Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session K1: Poster Session II (4:00pm-6:00pm)Poster
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Room: Exhibit Hall B |
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K1.00001: ATOM INTERFEROMETERS |
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K1.00002: Atom Interferometer inside a Hollow-Core Fiber Wui Seng Leong, Zilong Chen, Mingjie Xin, Shau-Yu Lan Light pulse atom interferometry under free fall is a common tool for gravity measurement at high precision level. However, its sensitivity scales with the size of experimental apparatus and optical power due to the diffraction of the Raman beam used in free space Mach-Zehnder interferometer. One of the solution is to use a waveguide such as single mode hollow-core fiber (HCF) to guide atoms and light simultaneously and perform interferometry in it. In this presentation, I will show the details of $\mathrm{Rb}^{85}$ atoms loaded into a hollow-core photonic crystal fiber. $\mathrm{Rb}^{85}$ atomic cloud of temperature $\sim100\mu\text{K}$ is prepared above the HCF. It is loaded into HCF by gravity pulling with the aid of a 1mK deep intra-HCF dipole trap. Rabi flopping, Ramsey fringes, and spin echo signal using 3.035 732 439 GHz microwave antenna for the transition $5^{2}\text{S}_{1/2}$ $F=2$ to $F=3$ and Raman beams with 1.276(2) GHz red detuned from $F=3\rightarrow F^{\prime}=2$ and $F=2\rightarrow F^{\prime}=2$ transition, are also demonstrated. Moreover, I will also show Mach-Zehnder interferometry signal, using $\frac{\pi}{2}-T-\pi-T-\frac{\pi}{2}$ sequence. [Preview Abstract] |
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K1.00003: Atom-chip-based interferometry with Bose-Einstein condensates Martina Gebbe, Sven Abend, Matthias Gersemann, Holger Ahlers, Hauke Muentinga, Sven Herrmann, Claus Laemmerzahl, Wolfgang Ertmer, Ernst M. Rasel Due to their small spatial and momentum width ultracold Bose-Einstein condensates (BEC) or even delta-kick collimated (DKC) atomic ensembles are very well suited for high precision atom interferometry and measure, for example, inertial forces with high accuracy. We generate such an ensemble in a miniaturized atom-chip setup, where BEC generation and DKC can be performed in a fast and reliable way. Using the chip as a retroreflector we have realized the first atom-chip-based gravimeter. All atom-optical operations including detection take place inside a volume of a one centimeter cube. In order to investigate new geometries we studied symmetric double Bragg diffraction as well as the coherent acceleration of atoms with Bloch oscillations. By combining both techniques we developed a novel relaunch mechanism, which we use to span a fountain geometry within our gravimeter. The relaunch increases the free fall time and, thus, enhances the device's sensitivity. Additionally, we employ these techniques to implement symmetric scalable large momentum beam splitters. [Preview Abstract] |
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K1.00004: Towards enhanced gravimetry with an optical cavity. Wanderson Pimenta, Mario Gonzalez, Ma. Soledad Billion, Alejandra Lopez-Vazquez, Georgina Olivares-Rentería, John Franco-Villafane, Eduardo Gomez Gravimetry uses Ramsey's separate field method with Raman transitions to accurately measure gravitational forces. Each atom interferes only with itself in the traditional gravimetry, giving an uncertainty that decreases as N-1/2 with N the number of atoms. An improved signal would be obtained using particles with higher mass. Our goal is to achieve collective interferometry, so that all atoms contribute coherently to the signal giving a better scaling of the uncertainty (as N-1). The present work gives a detailed description of the new atomic trap for collective interferometry in our laboratory. The vacuum system consists of a metal chamber with multiple windows for optical access connected to a combination of sorption and ion pumps. We use reentrant windows to avoid eddy currents generated by abrupt changes in the current of the coils. The optical components are mounted directly on the vacuum chamber using a cage system and we send the light through optical fibers. We monitor the atoms with a double relay imaging system to suppress background light. All the system is mounted in a passive isolation system to minimize vibrations. [Preview Abstract] |
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K1.00005: Low phase noise system for gravimetry Mario Gonzalez, Nieves Arias, Vahide Abediye, Eduardo Gomez The Raman beams required for atomic gravimetry involve two phase locked beams with different frequency. The traditional method uses two independent lasers with an optical phase lock loop to keep a fixed phase relation between them. Alternatively one can use a phase modulator to produce the required beams that are automatically phase locked. This method gives a simple system with a phase noise limited by the quality of the microwave synthesizer. Here, two Raman pairs are produced and they interfere with each other. We show that by using a calcite crystal we can change the relative polarization of the carrier and the sidebands. The destructive interference that appears in co-propagating Raman transitions is transformed into constructive interference with this method. We split the carrier and sidebands taking advantage of their different polarization and we send them in opposite directions to excite counter-propagating Raman transitions. By dialing the correct frequency we can select a particular direction for the momentum transfer. [Preview Abstract] |
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K1.00006: Design of an optical cavity for gravimetry M.S. Billion Reyes, A. Lopez-Vazquez, W. M. Pimenta, M.A. Gonzalez, J.A. Franco-Villafane, E. Gomez Atomic interferometry is a widely used method to perform precision measurements of accelerations. We enhance the interferometric signal by adding an optical cavity around the free-falling atoms inside of a vacuum chamber. We use a bow-tie configuration to support a traveling wave and avoid spatial fluctuations in the light shift. To induce collective behavior (entangled state), we design the optical cavity with a cooperativity factor higher than one. We present the characterization of an optical cavity with a maximized beam waist to reach homogeneous illumination of the atomic cloud. The mirrors have high reflectivity (R$=$99.999{\%}) at 780 nm, in a non-confocal arrangement so that we can excite transverse modes independently or simultaneously. We describe our progress to achieve a transverse mode closer to a flat-top and a cavity design that fits our geometrical restrictions. [Preview Abstract] |
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K1.00007: Versatile Atom Interferometer using a Single Diode Laser Xuejian Wu, Fei Zi, Ryan Bilotta, Jordan Dudley, Holger Mueller Light-pulse atom interferometry has been applied to measure gravity, Newton's gravitational constant and the fine structure constant with high precision. Miniature and transportable atom interferometers would open up more applications in geology, inertial navigation, and mineral exploration. Here, we demonstrate a compact atom interferometer for measuring gravity by use of a simplified laser system and a pyramid based magneto-optical trap. The laser system contains only a single distributed feedback laser. Both the repumping frequency and the Raman frequencies are generated from a fiber electro-optical modulator, and the Raman pulses are produced by acousto-optical modulators. In order to eliminate the AC Stark shift and balance the Rabi frequency and the single photon scattering, we choose a single photon detuning of 150 MHz red detuned from $F=$4$\to F$'$=$5 of cesium D$_{\mathrm{2}}$ transition. In the experiment, we capture 6 million atoms at 2 $\mu $K from the background vapor and achieve fringes with good visibility as the Raman pulse separation time is as long as tens of milliseconds in the Mach-Zehnder geometry. Additionally, multiple-axis measurement including three-axis acceleration and three-axis rotation is also possible in our atom interferometer with irradiating Raman pulses toward individual pyramid faces. Being simple, robust and multiple-axis capable, our versatile atom interferometer can be used for inertial sensing out of laboratory. [Preview Abstract] |
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K1.00008: Theoretical analysis of atom interferometry using a modulated laser John Alexander Franco Villafane, Georgina Olivares, Yasser Jeronimo Moreno, Eduardo Gomez Two-photon Raman transition has been a widely used technique in atom interferometry. However, the precision measurements are highly limited by the phase noise between the lasers involved in the Raman transition. To overcome this limitation atom interferometry using modulated Raman laser has been demonstrated experimentally recently in both counter- and co-propagating beams configuration. The theoretical analysis of this technique is far from being well understood. In this work, we will present an overview of the main challenges in the theoretical analysis of an atom interferometry using a modulated Raman laser. Some analytical solutions in limit cases are presented in counterpropagating configuration. [Preview Abstract] |
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K1.00009: Lukewarm lithium recoil interferometer Eric Copenhaver, Kayleigh Cassella, Brian Estey, Yanying Feng, Chen Lai, Müller Holger We demonstrate recoil-sensitive atom interferometry with laser-cooled lithium-7 at 50 times the recoil temperature. The large bandwidth of 160-ns beam-splitter pulses drives conjugate interferometers simultaneously with nearly equal contrast. Two-photon Raman transitions spectrally resolve the outputs, which thermally expand too quickly to be spatially resolved. Two images captured during a single exposure of a camera with slow readout detects both output ports. Optical pumping to a magnetically insensitive state using the well-resolved $D_1$ line suppresses magnetic dephasing and extends coherence time. Sensitivity comparable to interferometers utilizing large momentum transfer pulses is attainable at interrogation times on the order of 10 ms due to lithium’s high recoil frequency and the increased available atom number. Vibration noise is mitigated at this time scale and is converted to amplitude noise in our detection scheme, isolating the the recoil frequency from what is conventionally phase noise. These techniques relax requirements for cooling in recoil-sensitive interferometry, broadening the choice of species to particles that remain difficult to trap and cool, like electrons. [Preview Abstract] |
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K1.00010: Development of an Atom Interferometer Gravity Gradiometer for Earth Sciences Akash Rakholia, Alex Sugarbaker, Adam Black, Mark Kasevich, Babak Saif, Scott Luthcke, Lisa Callahan, Bernard D. Seery, Lee Feinberg, John C. Mather, Ritva Keski-Kuha We report progress towards a prototype atom interferometer gravity gradiometer for Earth science studies from a satellite in low Earth orbit. The terrestrial prototype has a target sensitivity of $8 \times 10^{-2} \mathrm{~E/Hz^{1/2}}$ and consists of two atom sources running simultaneous interferometers with interrogation time $T = 300 \mathrm{~ms}$ and $12\hbar k$ photon recoils, separated by a baseline of 2 m. By employing Raman sideband cooling and magnetic lensing, we will generate atomic ensembles with $N = 10^6$ atoms at a temperature of 3 nK. The sensitivity extrapolates to $7 \times 10^{-5} \mathrm{~E/Hz^{1/2}}$ in microgravity on board a satellite. Simulations derived from this sensitivity demonstrate a monthly time-variable gravity accuracy of 1 cm equivalent water height at 200 km resolution \footnote{S.B. Lutchke, \textit{et al.} In proceedings of the American Geophysical Union Fall Meeting, San Francisco, California, 2016}, yielding an improvement over GRACE by 1-2 orders of magnitude. A gravity gradiometer with this sensitivity would also benefit future planetary, lunar, and asteroidal missions. [Preview Abstract] |
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K1.00011: A large mode optical resonator for enhanced atom interferometry Ranjita Chanu Sapam, Nicolas Mielec, Isabelle Riou, Benjamin Canuel, David Holleville, Bess Fang, Arnaud Landragin, Remi Geiger The development of atom interferometry in the last few decades has led to high precision measurements of inertial effects and tests of fundamental physics. New methods for higher sensitivity atom interferometers (AIs) are being explored, particularly the interrogation of atoms with optical cavities\footnote{P. Hamilton et al, \textbf{Phys. Rev. Lett } 114, 100405 (2015)}. Its benefits would be higher optical power allowing large momentum transfer beam splitters, and possibly cleaner and controlled phase profiles. However high sensitivity AIs require long interrogation times, which combined with cold atom expansion, bring the challenges of large waists in cavities. We propose an optical resonator composed of a convergent lens with two flat mirrors at its focal planes\footnote{I. Riou , N. Mielec et al, \textbf{arXiv} 1701.01473 (2017)}. This cavity is marginally stable and exhibits half degenerate behaviour. A numerical study of its behaviour, using an ABCD transfer matrix formalism, showed that typical controllable misalignments of a few micrometres would not be critical for atom interrogation. We realise this cavity with a 200 mm lens and an 8 $\mu$m input waist and a 7 mm waist Gaussian beam inside the cavity. [Preview Abstract] |
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K1.00012: Characterizing the potential profile of an atom trap using tomographic fluorescence imaging Edward Moan, Tanwa Arpornthip, Charles Sackett We have developed a technique to fully characterize an arbitrary potential profile of an atom trap. A cold, but not condensed, atom cloud is first loaded into the trap and allowed to equilibrate. The trap is then turned off and the atoms are rapidly pumped into a dark state, such that they do not interact with light from a probe laser. A selected slice of the atom cloud is reactivated by repump light that is cylindrically focused into a light sheet with an appropriate thickness. The reactivated cross-sectional region interacts with the probe laser light to create a fluorescence image which is viewed perpendicular to the sheet. The light sheet can be translated to generate cross-section images of the cloud at different positions. Combing these cross-sections provides a full three dimensional profile of the atom cloud, much like tomographic imaging used in medical imaging. From the cloud profile the trap potential function is readily determined. We have demonstrated the technique using Rb atoms in a time-orbiting trap. We verified that the potential obtained had the correct anharmonic terms, when compared to an analysis of the trajectory of a Bose-Einstein condensate moving in the trap. The tomographic technique is both faster to acquire and in general simpler to analyze. [Preview Abstract] |
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K1.00013: Correcting for time-dependent field inhomogeneities in a time orbiting potential magnetic trap Adam Fallon, Seth Berl, Charles Sackett Many experiments use a Time Orbiting Potential (TOP) magnetic trap to confine a Bose-condensate. An advantage of the TOP trap is that it is relatively insensitive to deviations and errors in the magnetic field. However, precision experiments using the trapped atoms often do require the rotating field to be well characterized. For instance, precision spectroscopy requires accurate knowledge of both the field magnitude and field direction relative to the polarization of a probe laser beam. We have developed an RF spectroscopic technique to measure the magnitude of the field at arbitrary times within the TOP trap rotation period. From the time-variation mapped out, various imperfections can be isolated and measured, including asymmetries in the applied trap field and static environmental fields. By compensating for these imperfections, field control at the 10 mG level or better is achievable, for a bias field of 10 G or more. This should help enable more precision experiments using trapped condensates, including precision measurements of tune-out wavelengths and possibly parity-violation measurements. [Preview Abstract] |
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K1.00014: Enhancing Geometric Phases Sensitivity in Atomic Coupled Ring Interferometers by Modulating Inter-Ring Distance. John Toland, Eleni Romano Previous theoretical work in the study of transmission properties of cold atoms in coupled ring waveguide structures has indicated that the sensitivity to geometrical phase shifts be greatly enhanced by increasing the number of rings in the array or by changing the relative size of the rings in an array of the coupled waveguides. The coupled ring structures in these simulations assumed zero distance between rings. Our research addresses how increasing the inter-ring distance of the chain of $N$ rings affects the rotational sensitivity of a ring array interferometer. We determine the sensitivity of a ring array gyroscope by calculating the slopes of the transmission function with respect to phase at the sharpest transmission resonance in the transmission function. The distance between rings is parameterized as the product of the wave number $k$ and the distance between the rings d, while the size of the rings is parameterized by the product of k and the ring circumference $L$. The transmission is periodic with oscillatory regions and zero transmission gap regions. Our results show that modulating the inter-ring distance near $kd=0.5\pi$ leads to sharp transmission resonances with slopes that are orders of magnitude greater than those in ring arrays with directly connected rings. [Preview Abstract] |
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K1.00015: Toward a precision force sensor based on Bloch oscillations of atoms in an optical lattice Robert Niederriter, Chandler Schlupf, Eliot Bohr, Erik Szwed, Youna Park, Sami Khamis, Paul Hamilton Precision force sensors have potential for exploring and constraining unknown forces such as dark energy candidates [1]. We are developing a precision sensor that measures the force on ytterbium atoms optically trapped inside an optical cavity. The trapped and cooled atoms undergo Bloch oscillations which can be monitored for continuous force measurement [2]. Using trapped atoms allows long measurement times in a small volume. Continuous measurement enables detection of time-varying forces and reduces sensitivity to vibrations. The atoms for the force sensor are cooled and trapped in a two-dimensional magneto-optical trap (MOT) and loaded into a three-dimensional MOT within an optical cavity. We present progress towards the development of a precision force sensor and tests of new fundamental forces. [1] P. Hamilton, M. Jaffe, P. Haslinger, Q. Simmons, H. M{\"u}ller, J. Khoury, Science 349, 849 (2015). [2] B. Prasanna Venkatesh, M. Trupke, E. A. Hinds, and D. H. J. O’Dell, Phys. Rev. A 80, 063834 (2009). [Preview Abstract] |
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K1.00016: ATOMIC CLOCKS |
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K1.00017: A Cd$_{\mathrm{+}}$ microwave frequency standard based on dual-trap and sympathetic cooling. Yani Zuo, Pengfei Cheng, Xiaolin Sun, Jianwei Zhang, Lijun Wang The passive microwave atomic clocks are studied widely, and the frequency stability of the state-of-the-art ones are close to the quantum projection noise limit. Most of those frequency standards work in pulse mode, which means that there exits dead time in each locking cycle due to states initialization and detection, laser cooling. High frequency fluctuations of the local oscillator (LO) are down-conversed to the feedback loop to degrade the frequency stability, namely, Dick effect. The microwave frequency standard based on laser-cooled $_{\mathrm{113}}$Cd$_{\mathrm{+}}$ ions in our laboratory has similar issue. Although it achieved the frequency stability to 6e-13 $\tau_{\mathrm{-1/2}}$, it is far from the limit of theoretical performance. Analyses show that the Dick effect and RF heating are the two main limitations. Thus, we propose and design a new scheme to overcome these two limits by sympathetic cooling and interleaving lock. The $_{\mathrm{24}}$Mg$_{\mathrm{+}}$ ions cooled by 280nm laser are used to sympathetically cool the $_{\mathrm{113}}$Cd$_{\mathrm{+}}$ ions via Coulomb interaction to decrease the RF heating in ion traps. Meanwhile, two ion clouds in two identical ion traps are interrogated alternatively to lock the same LO to estimate dead time. The new scheme could improve the performance of the microwave atomic clocks greatly. [Preview Abstract] |
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K1.00018: Properties of Lu$^{2+}$ ion for the atomic clock development M. S. Safronova, W. R. Johnson, U. I. Safronova Significant bottleneck for further improvement of trapped ion clock accuracy arises from relatively low stability achievable with a single ion. A solution was proposed [1] that may allow to overcome this hurdle via the use of large ion crystals with a special scheme to cancel the effects of micromotion. The crucial condition for the implementation of such a scheme is the negative value of the scalar polarizability difference for the clock transition. Doubly ionized lutetium satisfies such a condition, and a potentially promising candidate for multi-ion clock development [2]. In this work, we study relevant parameters of Lu$^{2+}$, including transition matrix elements, lifetimes, polarizabilities, hyperfine constants and the blackbody radiation shift of the potential clock transition [3].\\ \noindent[1] K. J. Arnold \textit{et al.}, Phys. Rev. A 92, 032108 (2015).\\ \noindent[2] K. J. Arnold and M. D. Barrett (2016), arXiv:1607.04344.\\ \noindent[3] U. I. Safronova, M. S. Safronova, W. R. Johnson, Phys. Rev. A 94, 032506 (2016). [Preview Abstract] |
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K1.00019: Updates on the NIST ytterbium optical lattice clock Xiaogang Zhang, Roger Brown, Marco Schioppo, Kyle Beloy, William McGrew, Robert Fasano, Daniele Nicolodi, Holly Leopardi, Tara Fortier, Andrew Ludlow We present a summary of recent developments in an optical lattice clock based on ultracold ytterbium. By combining two lattice-trapped cold-atom systems to realize continuous laser interrogation, we demonstrate an optical clock with a fractional frequency instability of $6\times10^{-17}$ for an averaging time 1 s. The continuous laser interrogation scheme effectively eliminates the deleterious aliasing process which limits most optical clocks. By further decreasing the technical noise, it should be possible to realize quantum-limited stability due to quantum projection noise. We also characterize important systematic effects influencing the frequency uncertainty of the ytterbium optical lattice clock at the $10^{-18}$ level. Recent experimental studies of high-order lattice Stark shifts, including higher multipolarizabilities from magnetic dipole and electric quadrupole as well as hyperpolarizability, will be reported, together with DC stark effects, background gas shifts, residual Doppler effects, and more. [Preview Abstract] |
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K1.00020: Optical Atomic Clock for Fundamental Physics and Precision Metrology in Space Jason Williams, Thanh Le, Sascha Kulas, Nan Yu The maturity of optical atomic clocks (OC), which operate at optical frequencies for higher quality-factor as compared to their microwave counterparts, has rapidly progressed to the point where lab-based systems now outperform the record cesium clocks by orders of magnitude in both accuracy and stability. We will present our efforts to develop a strontium optical clock testbed at JPL, aimed towards extending the exceptional performance demonstrated by OCs from state-of-the-art laboratory designs to a transportable instrument that can fit within the space and power constraints of e.g. a single express rack onboard the International Space Station. The overall technology will find applications for future fundamental physics research, both on ground and in space, precision time keeping, and NASA/JPL time and frequency test capabilities. [Preview Abstract] |
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K1.00021: Frequency stability measurement of pulsed superradiance from strontium Matthew Norcia, Julia Cline, John Robinson, Jun Ye, James Thompson Superradiant laser light from an ultra-narrow optical transition holds promise as a next-generation of active frequency references. We have recently demonstrated pulsed lasing on the milliHertz linewidth clock transition in strontium. Here, we present the first frequency comparisons between such a superradiant source and a state of the art stable laser system. We characterize the stability of the superradiant system, and demonstrate a reduction in sensitivity to cavity frequency fluctuations of nearly five orders of magnitude compared to a conventional laser. [Preview Abstract] |
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K1.00022: A Fermi-degenerate three-dimentional optical lattice clock Akihisa Goban, Sara Campbell, Ross Hutson, G. Edward Marti, Lindsay Sonderhouse, John Robinson, Wei Zhang, Jun Ye The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, tighter limits on fundamental constant variation, and improved tests of relativity. Recent progress in optical lattice clock to the accuracy of 2E-18 has benefited from the understanding of atomic interactions. Also the precision of clock spectroscopy has been applied to explore many-body interactions including SU(N) symmetry. In our previous 1D optical lattice, atomic interactions cause suppression and broadening of the atomic resonance, limiting the clock stability. To overcome this limitation, we demonstrate a scalable solution that takes advantage of the high density of a degenerate Fermi gas in a three-dimensional optical lattice to protect against on-site interaction shifts. Using an ultrastable laser, we achieve an unprecedented level of atom-light coherence, reaching a spectroscopic quality factor 5.2E15. We investigate clock systematics unique to this design; on-site interactions are resolved so that their contribution to clock shifts is orders of magnitude suppressed compared to the 1D optical lattice experiments. Also, we measure the combined scalar and tensor magic wavelengths for state-independent trapping along all three lattice axes. [Preview Abstract] |
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K1.00023: A clock transition in a solid-state system G. J. A. Edge, S. Potnis, A. C. Vutha With the impending redefinition of the SI second based on optical frequency standards, new secondary frequency standards are needed in order to form clock ensembles. Ideally such secondary standards will offer enhanced robustness, portability and high signal-to-noise ratios (SNR), to enable rapid and precise comparisons to be made against primary standards. A clock based on a narrow optical transition, in atoms that are doped into a solid-state host, offers the experimental simplicity and large SNR to satisfy these requirements. The intra-configuration $^7F_0 \to \, ^5D_0$ transition, in Sm$^{2+}$ ions doped into a host crystal, is an attractive candidate for such secondary standards due to its low susceptibility to perturbations from the crystal environment. We present results from the interrogation of this clock transition with a narrow linewidth laser. [Preview Abstract] |
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K1.00024: A compact apparatus for a two-photon optical clock S. Potnis, S. Jackson, A. C. Vutha The Doppler- and recoil-free nature of two-photon transitions eliminates the need for atoms in optical clocks to be trapped at ultracold temperatures. The resulting technical simplicity makes atoms with narrow two-photon transitions attractive candidates for portable optical frequency standards. We report on progress towards the construction of a two-photon optical clock based on the 915 nm $4s^{2}\,^{1}S_{0} \rightarrow\rightarrow 4s3d\,^{1}D_{2}$ transition in calcium atoms. We demonstrate laser cooling of calcium in a compact and portable apparatus, and report on the performance of two narrow-linewidth 915 nm lasers. [Preview Abstract] |
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K1.00025: ELECTRIC-DIPOLE SEARCHES AND TESTS OF FUNDAMENTAL SYMMETRIES |
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K1.00026: EDM measurements on cold $^{\mathrm{225}}$Ra and $^{\mathrm{171}}$Yb atoms Tian Xia, Matthew Dietrich, Zheng-Tian Lu EDM measurements on diamagnetic atoms probe CP-violating effects in the nucleus. Some types of these Beyond-Standard-Model effects are known to be strongly enhanced in $^{\mathrm{225}}$Ra due to octupole deformation of the nucleus. Other favorable characteristics of $^{\mathrm{225}}$Ra include a high atomic number (Z $=$ 88), a ground state of $^{\mathrm{1}}$S$_{\mathrm{0}}$, and a nuclear spin 1/2. An EDM search is carried out on this radioactive isotope (half-life 15 d) using laser-cooled atoms. Meanwhile, the stable isotope $^{\mathrm{171}}$Yb shares several characteristics, including $^{\mathrm{1}}$S$_{\mathrm{0}}$ and nuclear spin 1/2, and is particularly useful as a proxy of $^{\mathrm{225}}$Ra for developing laser trapping and probing techniques, for testing various measurement schemes, and for investigating systematic errors. Furthermore, $^{\mathrm{171}}$Yb atoms can be placed within 0.1 mm of $^{\mathrm{225}}$Ra, and act as a co-magnetometer. A laser trap of Yb atoms for an EDM measurement is under development. [Preview Abstract] |
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K1.00027: High precision measurement of T-symmetry violation in an atomic nucleus: Initial progress. Konrad Wenz, Eric B. Norrgard, David DeMille, David Kawall, Tanya Zelevinsky We discuss the plans and initial progress of an experimental search for an electric dipole moment (EDM) of a thallium nucleus by exploiting its Schiff moment. Our experiment relies on optical and microwave quantum-state manipulation and interrogation of a cold molecular beam. The sensitivity to the QCD $\theta $ parameter in the first generation is projected to be 30-fold improved compared to previous measurements. The apparatus being designed by our CENTREX collaboration relies on a cryogenic source that provides an intense, cold beam of thallium fluoride. The EDM measurement will utilize the molecular ground state, enabling us to take advantage of a long interaction region, where an applied electric field will strongly polarize the molecules and cause precession of the EDM. Recent progress includes construction and testing of ultraviolet light sources for optical manipulations of TlF, as well as designing the detection region with applied microwaves, detection light, and a high collection efficiency of cycling optical photons. We also simulate a molecule ``lens'' that focuses the molecular beam in the detection region using a quadrupole electric field and the J$=$3 rotational state of the molecules. [Preview Abstract] |
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K1.00028: Improvements to the YbF electron electric dipole moment experiment B. E. Sauer, I. M. Rabey, J. A. Devlin, M. R. Tarbutt, C. J. Ho, E. A. Hinds The standard model of particle physics predicts that the permanent electric dipole moment (EDM) of the electron is very nearly zero. Many extensions to the standard model predict an electron EDM just below current experimental limits. We are currently working to improve the sensitivity of the Imperial College YbF experiment.\footnote{J. J. Hudson et al., Nature, \textbf{473}(7348), 493-U232 (2011).} We have implemented combined laser-radiofrequency pumping techniques which both increase the number of molecules which participate in the EDM experiment and also increase the probability of detection. Combined, these techniques give nearly two orders of magnitude increase in the experimental sensitivity. At this enhanced sensitivity magnetic effects which were negligible become important. We have developed a new way to construct the electrodes for electric field plates which minimizes the effect of magnetic Johnson noise.\footnote{I. M. Rabey, J. A. Devlin, E. A. Hinds, B. E. Sauer, Rev. Sci. Inst. \textbf{87} 115110 (2016).} The new YbF experiment is expected to comparable in sensitivity to the most sensitive measurements of the electron EDM to date. We will also discuss laser cooling techniques which promise an even larger increase in sensitivity. [Preview Abstract] |
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K1.00029: Current results and future directions for an electron electric dipole moment search using molecular ions William B. Cairncross, Daniel N. Gresh, Yan Zhou, Kia Boon Ng, Tanya Roussy, Yuval Shagam, Fatemeh Abbasi Razgaleh, Parker Hinton, Jun Ye, Eric A. Cornell We recently completed a first measurement of the electron’s electric dipole moment (eEDM) using trapped HfF$^+$ ions, which we will present along with accompanying systematic error analysis. We will also detail our ongoing progress towards a second generation measurement with HfF$^+$, including characterizations of our second generation ion trap. Finally, we will present LIF spectroscopy of ThF for the efficient production of ThF$^+$, a species that possesses higher eEDM sensitivity than HfF$^+$, as well as the potential for very long interrogation times with high immunity to systematic errors via electron spin resonance spectroscopy in its ground $^{3}\Delta_1$ electronic state [1]. \\[4pt] [1] Daniel N.~Gresh, Kevin C.~Cossel, Yan Zhou, Jun Ye, and Eric A.~Cornell, J.~Mol.~Spec.~\textbf{319}, 1 (2016) [Preview Abstract] |
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K1.00030: Design and Operation of the ATRAP Low-Inductance Ioffe Trap Eric Tardiff, Christopher Hamley, Nathan Jones, Ghanshyambhai Khatri, Gerald Gabrielse, Cole Meisenhelder, Tharon Morrison, Siu Au Lee, Cory Rasor, Samuel Ronald, Dylan Yost, Bartosz Glowacz, Marcin Zielinski, Dieter Grzonka, Daniel Zambrano, Olga Andriyevska, Eric Hessels, Taylor Skinner, Cody Storry The ATRAP experiment aims to perform Lyman alpha cooling and 1S-2S spectroscopy of trapped antihydrogen atoms for a precision test of CPT symmetry. Our upgraded experimental apparatus includes a neutral-particle confining Ioffe trap that features several improvements over the previous generation. This Ioffe trap can run in both octupole and quadrupole configurations, be shut off in tens of milliseconds for reduced cosmic ray background over the antihydrogen annihilation window, and be fully energized in a few minutes. This allows for a much reduced duty cycle. As in the previous generation, it features four radial ports, allowing for three-axis laser access to the trapping volume. Commissioning tests have been completed and show that we can reliably energize the trap to depths of at least 405 mK (octupole) or 513 mK (quadrupole). [Preview Abstract] |
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K1.00031: Constructing a Laser Stabilization System for a Parity Non-Conservation Experiment with Francium A.C. DeHart, Gerald Gwinner, Michael Kossin, John Behr, Alexandre Gorelov, Mukut Kalita, Matthew Pearson, Seth Aubin, Eduardo Gomez Garcia, Luis Orozco We are developing an experiment at TRIUMF to test the Standard model at low energies by measuring Parity Non-Conservation (PNC) effects in francium. Current efforts include preparations to study the 7s -- 8s electric dipole (E1) forbidden transition in francium at 507 nm under the influence of an electric field. Fr has no stable isotope; therefore to frequency-stabilize our laser at 507 nm, we are developing a laser stabilization system by using the Pound-Drever-Hall technique with a Fabry-Perot cavity made of Ultra Low Expansion Glass (ULE) as our stable frequency reference. The system will stabilize a 1014 nm laser, which will be frequency doubled to 507 nm, before sending the light to our cold and trapped francium sample. We will report on our recent experiences with the laser stabilization system. [Preview Abstract] |
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K1.00032: Progress Towards an Order of Magnitude Improvement on the Measurement of the Electron Electric Dipole Moment Daniel Ang, David DeMille, John Doyle, Gerald Gabrielse, Jonathan Haefner, Zack Lasner, Cole Meisenhelder, Cristian Panda, Adam West, Elizabeth West The search for the electron electric dipole moment (eEDM) is a powerful probe of fundamental physics beyond the Standard Model. In 2014, the first generation of the ACME experiment set the most stringent upper limit on the eEDM of $|d_e|<1\times10^{−28}~e \cdot cm$ by means of measuring spin precession in a beam of thorium monoxide (Science 343 (2014), 269-272). Since then, we have implemented various improvements, such as STIRAP preparation of the experimental H state, rotational cooling, optimized apparatus geometry, and enhanced detection efficency, boosting our signal by a factor of about 400. We have also devised means to reduce the leading systematics we found in the Generation I experiment. We describe the recent progress in taking data using our Generation II apparatus and our ongoing efforts to investigate various systematics. [Preview Abstract] |
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K1.00033: Future Improvements to the ACME Electric Dipole Moment Experiment Jonathan Haefner, Daniel Ang, Jacob Baron, David DeMille, John Doyle, Gerald Gabrielse, Nicholas Hutzler, Zack Lasner, Cole Meisenhelder, Cristian Panda, Adam West, Elizabeth West In 2014, the ACME collaboration set a new upper bound on the electric dipole moment of the electron using beams of cold ThO. We discuss studies into further improvements to the ACME experiment, with the eventual goal of sensitivity at the $10^{-30} \; e \; \textup{cm}$ level, a factor of 100 smaller than the first generation experiment. Methods focus primarily on improving statistics, and include the use of an electrostatic or magnetic molecular beam focusing lens, optical cycling to improve detection, and the use of a new thermochemical beam source to increase molecule number. [Preview Abstract] |
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K1.00034: FLOQUENT PHYSICS |
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K1.00035: A graph-theoretical representation of multiphoton resonance processes in artificial atoms. Hossein Z. Jooya, Shih-I Chu We propose a graph-theoretical formalism to study generic circuit quantum electrodynamics systems consisting of a two level qubit coupled with a single-mode resonator in arbitrary coupling strength regimes beyond rotating-wave approximation. We define colored-weighted graphs, and introduce different products between them to investigate the dynamics of superconducting qubits in transverse, longitudinal, and bidirectional coupling schemes. The intuitive and predictive picture provided by this method, and the simplicity of the mathematical construction, are demonstrated with some numerical studies of the multiphoton resonance processes and quantum interference phenomena for the superconducting qubit systems driven by intense ac fields. [Preview Abstract] |
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K1.00036: Direct Observation of Topological Invariants using Quantum Walks Vinay Ramasesh, Emmanuel Flurin, Shay Hacohen-Gourgy, Leigh Martin, Irfan Siddiqi, Norman Yao Quantum walks are generalizations of the classical random walk in which the walking particle is endowed with an internal degree of freedom and can exist on a superposition of lattice sites. Initially investigated as a possible replacement for classical random walks in randomized algorithms, quantum walks have since found numerous applications, including the possibility of performing universal quantum computation and simulating interacting systems. More recently, it was realized that quantum walks also possess topological properties. Like spin-orbit coupled Hamiltonians in condensed matter physics, the effective band-structures corresponding to quantum walks feature topological invariants robust to local deformations. Here, we propose and analyze a new class of quantum walks, termed Bloch-oscillating-quantum-walks and demonstrate that such algorithms can directly probe the underlying band topology. Moreover, we present the first experimental measurement of a topological invariant in a quantum walk, performed in a cavity quantum electrodynamics architecture. [Preview Abstract] |
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K1.00037: Investigation of a driven fermionic system and detecting chiral edge modes in an optical lattice Frederik Görg, Michael Messer, Gregor Jotzu, Kilian Sandholzer, Rémi Desbuquois, Nathan Goldman, Tilman Esslinger Periodically driven systems of ultracold fermions in optical lattices allow to implement a large variety of effective Hamiltonians through Floquet engineering. An important question is whether this method can be extended to interacting systems. We investigate driven two-body systems in an array of double wells and measure the double occupancy and the spin-spin correlator in the large frequency limit and when driving resonantly to an energy scale of the underlying static Hamiltonian. We analyze whether the emerging states of the driven system can be adiabatically connected to states in the unshaken lattice. In addition, we measure the amplitude of the micromotion which describes the short time dynamics of the system and compare it directly to theory. In another context we propose a method to create topological interfaces and detect chiral edge modes in a two dimensional optical lattice. We illustrate this through an optical lattice realization of the Haldane model for cold atoms, where an additional spatially-varying lattice potential induces distinct topological phases in separated regions of space. [Preview Abstract] |
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K1.00038: Discrete time-crystalline order in black diamond Hengyun Zhou, Soonwon Choi, Joonhee Choi, Renate Landig, Georg Kucsko, Junichi Isoya, Fedor Jelezko, Shinobu Onoda, Hitoshi Sumiya, Vedika Khemani, Curt von Keyserlingk, Norman Yao, Eugene Demler, Mikhail D. Lukin The interplay of periodic driving, disorder, and strong interactions has recently been predicted to result in exotic ''time-crystalline'' phases, which spontaneously break the discrete time-translation symmetry of the underlying drive. Here, we report the experimental observation of such discrete time-crystalline order in a driven, disordered ensemble of $\sim 10^6$ dipolar spin impurities in diamond at room-temperature. We observe long-lived temporal correlations at integer multiples of the fundamental driving period, experimentally identify the phase boundary and find that the temporal order is protected by strong interactions; this order is remarkably stable against perturbations, even in the presence of slow thermalization. Our work opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems. [Preview Abstract] |
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K1.00039: Demonstration of the Kibble-Zurek mechanism in a non-equilibrium phase transition Yogesh S Patil, Hil F H Cheung, Aditya G Date, Mukund Vengalattore We describe the experimental realization of a driven-dissipative phase transition (DPT) in a mechanical parametric amplifier and demonstrate key signatures of a critical point in the system, where the susceptibilities and relaxation time scales diverge and coincide with the spontaneous breaking of symmetry and the emergence of macroscopic order. While these observations are reminiscent of equilibrium phase transitions, it is presently an open question whether such DPTs are amenable to the conventional Landau-Ginsburg-Wilson paradigm that relies on concepts of scale invariance and universality -- Indeed, recent theoretical work has predicted that DPTs can exhibit phenomenology that departs from these conventional paradigms [1]. By quenching the system past the critical point, we measure the dynamics of the emergent ordered phase and its departure from adiabaticity, and find that our measurements are in excellent agreement with the Kibble-Zurek hypothesis. In addition to validating the KZ mechanism in a DPT for the first time, we also uniquely show that the measured critical exponents accurately reflect the interplay between the intrinsic coherent dynamics and the environmental correlations, with a clear departure from mean field exponents in the case of non-Markovian system-bath interactions. We also discuss how the techniques of reservoir engineering and the imposition of artificial environmental correlations can result in the stabilization of novel many-body quantum phases and exotic non-equilibrium states of matter. [1] L. M. Sieberer et al., Phys. Rev. Lett. 110, 195301 [Preview Abstract] |
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K1.00040: Long-range Prethermal Time Crystals Francisco Machado, Gregory D. Meyer, Dominic Else, Christopher Olund, Chetan Nayak, Norman Y. Yao Driven quantum systems have recently enabled the realization of a discrete time crystal --- an intrinsically out-of-equilibrium phase of matter. One strategy to prevent the drive-induced, runaway heating of the time crystal is the presence of strong disorder leading to many-body localization (MBL). A more elegant, disorder-less approach is simply to work in the prethermal regime where time crystalline order can persist to exponentially long times. One key difference between prethermal and MBL time crystals is that the former is prohibited from existing in one dimensional systems with short-range interactions. In this work, we demonstrate that long-range interactions can stabilize a one dimensional prethermal time crystal. By numerically studying the pre-thermal regime, we find evidence for a phase transition out of the time crystal as a function of increasing energy density. Finally, generalizations of previous analytical bounds for the heating time-scale of driven quantum systems to long-range interactions will also be discussed. [Preview Abstract] |
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K1.00041: SYNTHETIC GAUGE FIELDS AND SPIN-ORBIT COUPLING IN COLD GASES |
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K1.00042: Spin-orbit coupling in ultracold Fermi gases of $^{173}$Yb atoms Bo Song, Chengdong He, Elnur Hajiyev, Zejian Ren, Bojeong Seo, Geyue Cai, Dovran Amanov, Shanchao Zhang, Gyu-Boong Jo Synthetic spin-orbit coupling (SOC) in cold atoms opens an intriguing new way to probe nontrivial topological orders beyond natural conditions. Here, we report the realization of the SOC physics both in a bulk system and in an optical lattice. First, we demonstrate two hallmarks induced from SOC in a bulk system, spin dephasing in the Rabi oscillation and asymmetric atomic distribution in the momentum space respectively. Then we describe the observation of non-trivial spin textures and the determination of the topological phase transition in a spin-dependent optical lattice dressed by the periodic Raman field. Furthermore, we discuss the quench dynamics between topological and trivial states by suddenly changing the band topology. Our work paves a new way to study non-equilibrium topological states in a controlled manner. [Preview Abstract] |
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K1.00043: Few-body bound states near free-space $p$-wave resonances in the presence of single-particle spin-orbit coupling terms D. Blume, Q. Guan Ultracold atom systems provide unique opportunities for studying extremely weakly-bound two- and few-body states. Theoretically, many aspects of such bound states have been explored successfully using zero-range $s$-wave contact interactions. Experimentally, bound state spectra have been deduced using radio-frequency spectroscopy. This work considers weakly-bound two- and few-body states in the vicinity of two-body free-space $p$-wave scattering resonances in the presence of spin-orbit coupling. While it has been shown previously that the single-particle spin-orbit coupling terms have a profound effect on the two- and three-body bound state energies for $s$-wave interacting systems, the interplay between two-body $p$-wave interactions and single-particle spin-orbit coupling terms is much less studied. This contribution discusses our implementation of the explicitly correlated Gaussian basis set expansion approach and the dependence of the resulting two- and few-body energy spectra on the free-space scattering volume, the two-body effective range, and the spin-orbit coupling parameters such as the Raman coupling strength and the detuning. [Preview Abstract] |
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K1.00044: New forms of spin-orbit coupling in a strontium optical lattice clock Michael Perlin, Arghavan Safavi-Naini, Roee Ozeri, Ana Maria Rey Ultracold atomic systems allow for the simulation of a variety of condensed matter phenomena, including spin-orbit coupling (SOC), a key ingredient behind recently discovered topological insulators and a path for the realization of topological superfluids. While many experimental efforts have used alkali atoms to engineer SOC via Raman transitions, undesirable heating mechanisms have limited the observation of many-body phenomena manifest at long timescales. Alkaline earth atoms (AEA) have been recently shown to be a potentially better platform for the implementation of SOC due to their reduced sensitivity to spontaneous emission [1,2,3]. While previous work has used electronic clock states as a pseudo-spin degree of freedom, we consider the effects of clock side-band transitions. We discuss the richer SOC dynamics which emerges as a result of this extension, and present methods to probe these dynamics in current AEA optical lattice clocks. [1] Galitski, V. and Spielman, I.B., ``Spin-orbit coupling in quantum gases." Nature 494.7435 (2013): 49-54. [2] Kolkowitz, S., et al. ``Spin–orbit-coupled fermions in an optical lattice clock." Nature (2016). [3] Wall, M.L., et al. ``Synthetic spin-orbit coupling in an optical lattice clock." Physical review letters 116.3 (2016): 035301. [Preview Abstract] |
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K1.00045: Scattering resonances in a low-dimensional Rashba-Dresselhaus spin-orbit coupled quantum gas Su-Ju Wang, D. Blume Confinement-induced resonances allow for the tuning of the effective one-dimensional coupling constant. When the scattering state associated with the ground transverse mode is brought into resonance with the bound state attached to the energetically excited transverse modes, the atoms interact through an infinitely strong repulsion. This provides a route to realize the Tonks-Girardeau gas. On the other hand, the realization of synthetic gauge fields in cold atomic systems has attracted a lot of attention. For instance, bound-state formation is found to be significantly modified in the presence of spin-orbit coupling in three dimensions. This motivates us to study ultracold collisions between two Rashba-Dresselhaus spin-orbit coupled atoms in a quasi-one-dimensional geometry. We develop a multi-channel scattering formalism that accounts for the external transverse confinement and the spin-orbit coupling terms. The interplay between these two single-particle terms is shown to give rise to new scattering resonances. In particular, it is analyzed what happens when the scattering energy crosses the various scattering thresholds that arise from the single-particle confinement and the spin-orbit coupling. [Preview Abstract] |
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K1.00046: Microscopy of the interacting Harper-Hofstadter model in the few-body limit M. Eric Tai, Alexander Lukin, Matthew Rispoli, Robert Schittko, Tim Menke, Dan Borgnia, Philipp Preiss, Fabian Grusdt, Adam Kaufman, Markus Greiner The interplay of magnetic fields and interacting particles can lead to exotic phases of matter exhibiting topological order and high degrees of spatial entanglement. While these phases were discovered in a solid-state setting, recent techniques have enabled the realization of gauge fields in systems of ultracold neutral atoms, offering a new experimental paradigm for studying these novel states of matter. This complementary platform holds promise for exploring exotic physics in fractional quantum Hall systems due to the microscopic manipulation and precision possible in cold atom systems. However, these experiments thus far have mostly explored the regime of weak interactions. Here, we show how strong interactions can modify the propagation of particles in a $2 \times N$, real-space ladder governed by the Harper-Hofstadter model. We observe inter-particle interactions affect the populating of chiral bands, giving rise to chiral dynamics whose multi-particle correlations indicate both bound and free-particle character. The novel form of interaction-induced chirality observed in these experiments demonstrates the essential ingredients for future investigations of highly entangled topological phases of many-body systems. [Preview Abstract] |
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K1.00047: Studies of dressed states with coupling between spin and orbital-angular-momentum in a Bose condensate Yu-Ju Lin, Hong-Ren Chen, Pao-kang Chen, Kuan-Yu Lin, Hung-Ji Wei, Neng-Chun Chiu We Raman-couple bare spin states of a Bose condensate with a transfer of orbital-angular-momentum (OAM), where one of the Raman beams is a Laguerre Gaussian beam. The dressed spin state in such systems is a superposition state consisting of bare spin states with different OAM. We characterize the spin texture, relevant gauge potentials and lifetime of these dressed states; it is studied in both trap geometries of harmonic potentials and ring-shaped potentials. [Preview Abstract] |
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K1.00048: Observation of the supersolid stripe phase in spin-orbit coupled Bose-Einstein condensates Junru Li, Jeongwon Lee, Wujie Huang, Sean Burchesky, Boris Shteynas, Furkan Top, Alan Jamison, Wolfgang Ketterle Supersolidity combines the property of superfluid flow with long-range spatial periodicity of solids and has not been observed since predicted in condensed matter systems. The concept of supersolidity was then generalized to include other superfluid systems which break continuous translational symmetry. Bose-Einstein condensates with spin-orbit coupling are predicted to possess a stripe phase with supersolid properties. Here we report the first observation of the predicted density modulation of the stripe phase using Bragg reflection -- the evidence for spontaneous long-range order in one direction while maintaining a sharp momentum distribution -- the hallmark of superfluid Bose-Einstein condensates. In our system, the spin-orbit coupling was realized in an optical superlattice as described in [1]. Briefly two lowest bands in the superlattice were used as pseudospins and a Raman process was implemented to provide coupling between pseudospin and momentum. Our work establishes a system with unique continuous symmetry breaking properties, associated Goldstone modes and superfluid behavior.~ References: [1] J. Li \textit{et. al }PRL \textbf{117}.185301 [2] J. Li \textit{et. al }arXiv:1610.08194 [Preview Abstract] |
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K1.00049: NONLINEAR DYNAMICS AND OUT OF EQUILIBRIUM TRAPPED GASES |
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K1.00050: One-body density-matrix characterization of many-body localization Fabian Heidrich-Meisner, Soumya Bera, Thomas Martynec, Henning Schomerus, Jens Bardarson We present a comprehensive analysis of the one-body density matrix (OPDM) in a system of interacting fermions in the presence of disorder in a one-dimensional lattice. We show that the eigenstates of the OPDM are localized/delocalized in the many-body localized (MBL)/ergodic phase while the eigenvalues exhibit a characteristic discontinuity in MBL phase reminiscent of the momentum distribution function of a zero-temperature Fermi-liquid [1]. Based on these results, we discuss the connection of OPDM eigenstates to quasi-particle-like integrals of motion in the MBL phase [2]. [1] Bera et al. Phys. Rev. Lett. 115, 046603 (2015) [2] Bera et al. arXiv:1611.01687 [Preview Abstract] |
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K1.00051: Measuring commutator square in nuclear spin systems Xuan Wei, Chandrasekhar Ramanathan, Paola Cappellaro Out-of-time ordered correlations (OTOC) have recently received much attention due to their unique ability to probe information scrambling in many-body quantum systems. As a result OTOC have been fruitfully applied to the study of quantum chaos, many-body localization, and quantum phase transitions. We provide experimental measurements of the commutator square, akin to OTOC, in a disordered interacting spin chain at effectively infinite temperature. We observe a slow growth of the commutator square consistent with slow information scrambling in disordered systems. We also measure the commutator square in a system exhibiting a phase transition; we observe the commutator square to grow the fastest near the critical point. [Preview Abstract] |
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K1.00052: Quantum dynamics of dynamically unstable, integrable few-mode systems Ranchu Mathew, Eite Tiesinga Recently, quenches in isolated ultra-cold atomic quantum systems have become a subject of intense study. We consider quantum few-mode systems that are integrable in their classical mean-field limit and become dynamically unstable after a quench of a system parameter. Specifically, we study the cases of a Bose-Einstein condensate (BEC) in a double-well potential and of an antiferromagnetic $F=1$ spinor BEC constrained to a single spatial mode. First, we study the time dynamics of a coherent state after the quench within the truncated Wigner approximation and find that due to phase-space mixing the systems relax to a steady state. Using action-angle formalism and guided by insights from the related pendulum system, we obtain analytical expressions for the time evolution of expectation values of observables and their long-time values. We also study the full quantum dynamics of the systems. Comparing their results with the TWA results, we find agreement in the long-time expectation value of the observables. The relaxation time scales, however, are different. [Preview Abstract] |
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K1.00053: Modulational instability and its role in the formation of matter-wave soliton trains De Luo, Jason H. V. Nguyen, Randall G. Hulet Modulational instability (MI) is a process by which perturbations at a critical wavelength in a waveform grow exponentially due to the interplay between a focusing nonlinearity and dispersion. The break-up of the waveform can lead to the formation of soliton trains. It was observed that matter-wave soliton trains form from a Bose-Einstein condensate, after an interaction quench from a repulsive to an attractive nonlinearity\footnote{K. E. Strecker, G. B. Partridge, A. G. Truscott, and R. G. Hulet, Nature 417, 150 (2002)}. An alternating phase structure was inferred from the dynamics of the soliton train, in which adjacent solitons repel one another. The mechanism by which the phase structure develops remains unclear. In this work, we examine the role of MI in the formation of the matter-wave soliton trains. We confirm that MI correctly predicts the number of solitons and the time-scale of the formation process. With real-time imaging, we provide evidence that the soliton train is born with an alternating phase structure, rather than evolving into one. [Preview Abstract] |
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K1.00054: Superradiance and dynamical instability in an illuminated BEC William Lunden, Jesse Amato-Grill, Ivana Dimitrova, Niklas Jepsen, Wolfgang Ketterle An elongated, trapped Bose-Einstein condensate illuminated by an off-resonant laser beam has been used as a platform to observe superradiant Rayleigh scattering for almost two decades. We now consider the case of an elongated BEC illuminated by a pair of non-interfering, off-resonant lasers, and explore the dynamics of the coupled light-matter system in the short-time regime (i.e., times on the order of the inverse of the single-photon recoil frequency). In particular, we look for signatures of a proposed dynamical instability in the coupled system which spontaneously breaks the translational symmetry of both the BEC density and the total light field's intensity profile along the long axis of the trap. We also explore the relative roles of the spontaneous light force and the dipole force in both superradiance and this dynamical instability. [Preview Abstract] |
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K1.00055: Influence of system-bath interactions on driven-dissipative phase transitions Hil F H Cheung, Yogesh S Patil, Mukund Vengalattore A wide range of non-equilibrium systems exhibit signatures of critical behavior and phase transitions such as critical slowing down, divergent correlation lengths and susceptibilities. Such signatures are coincident with the emergence of macroscopic phases due to the interplay between the coherent system dynamics and dissipation to the environment. In contrast to equilibrium physical systems, the physical mechanisms that give rise to this order involve both the system and the environment. Due to the different origins of these mechanisms, such driven-dissipative transitions can exhibit dynamical phase transitions where the critical behavior lies beyond the conventional universality classes of equilibrium phase transitions [1]. We describe such a driven-dissipative phase transition in a parametric oscillator-amplifier system and demonstrate that the system exhibits key signatures of a continuous phase transition, including a spontaneously broken symmetry and the emergence of goldstone modes. In contrast to an equilibrium phase transition, we show that the phase diagram and emergent phases crucially depend on the environmental correlations and that as such, can be modified by the imposition of correlations beyond the Markovian regime. We also discuss the extension of this description of universal behavior near criticality in driven-dissipative phase transitions to lower dimensions. [1] L. M. Sieberer et al., Phys. Rev. Lett. 110, 195301 [Preview Abstract] |
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K1.00056: The Kibble-Zurek mechanism in phase transitions of non-equilibrium systems Hil F H Cheung, Yogesh S Patil, Aditya G Date, Mukund Vengalattore We experimentally realize a driven-dissipative phase transition using a mechanical parametric amplifier to demonstrate key signatures of a second order phase transition, including a point where the susceptibilities and relaxation time scales diverge, and where the system exhibits a spontaneous breaking of symmetry. Though reminiscent of conventional equilibrium phase transitions, it is unclear if such driven-dissipative phase transitions are amenable to the conventional Landau-Ginsburg-Wilson paradigm, which relies on concepts of scale invariance and universality, and recent work has shown that such phase transitions can indeed lie beyond such conventional universality classes [1]. By quenching the system past the critical point, we investigate the dynamics of the emergent ordered phase and find that our measurements are in excellent agreement with the Kibble-Zurek mechanism. In addition to verifying the Kibble-Zurek hypothesis in driven-dissipative phase transitions for the first time, we also demonstrate that the measured critical exponents accurately reflect the interplay between intrinsic coherent dynamics and environmental correlations, showing a clear departure from mean field exponents in the case of non-Markovian system-bath interactions. We further discuss how reservoir engineering and the imposition of artificial environmental correlations can result in the stabilization of novel many-body quantum phases and aid in the creation of exotic non-equilibrium states of matter. [1] L. M. Sieberer et al., Phys. Rev. Lett. 110, 195301 [Preview Abstract] |
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K1.00057: Multicomponent solitons in dilute-gas BECs Vandna Gokhroo, Thomas M. Bersano, M. A. Khamehchi, Peter Engels Dilute-gas Bose-Einstein condensates can host an intriguing variety of nonlinear structures. In effectively one-dimensional geometries, solitonic excitations play a prominent role. While soliton physics in general is very rich, only a limited number of soliton types have been realized in BECs so far. Here we report on the experimental observation of novel types of solitons in multicomponent systems, including the dark-antidark soliton which is related to the recently introduced notion of magnetic solitons in BECs. [Preview Abstract] |
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K1.00058: LONG RANGE INTERACTIONS IN COLD GASES |
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K1.00059: Non-local dark solitons in dipolar condensates Matthew Edmonds, Thomas Bland, Nick Parker Dark solitons are fundamental one-dimensional excitations supported in defocussing nonlinear media, and have been observed and studied extensively in the atomic Bose-Einstein condensates. In dipolar condensates, for which the constituent atoms possess large magnetic moments, the conventional isotropic, local nonlinearity is supplemented by anisotropic, non-local nonlinearity [1]. Here we establish the properties of dark solitons in dipolar condensates, from their family of solutions and collision dynamics in homogeneous systems [2,3,4] to their oscillations in trapped condensates [5]. The non-locality of the dark soliton leads to a plethora of unconventional and intriguing behaviours, including density ripples around the soliton core, bound states and interaction-dependent oscillations. REFERENCES: [1] T. Lahaye, et al, Rep. Prog. Phys. 72, 126401 (2009) [2] K. Pawlowski and K. Rzazewski, New J. Phys. 17, 105006 (2015) [3] T. Bland, M. J. Edmonds, N. P. Proukakis, A. M. Martin, D. H. J. O'Dell and N. G. Parker, Phys. Rev. A 92, 063601 (2015) [4] M. J. Edmonds, T. Bland, D. H. J. O'Dell and N. G. Parker, Phys. Rev. A 93, 063617 (2016) [5] T. Bland et al., arXiv:1610.02002 (2016) [Preview Abstract] |
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K1.00060: Quantum walks of interacting particles in low-dimensional lattices Tirthaprasad Chattaraj, Roman Krems We study the effects of long-range hopping and long-range interparticle interactions on the quantum walk of hard-core bosons in ideal and disordered lattices. We find that the range of hopping has a much more significant effect on the particle correlation dynamics than the range of interactions. While attractively and repulsively interacting pairs with short-range hopping in 1D lattices undergo the same dynamics, long-range hopping introduces asymmetry with respect to the sign of the interaction. We examine the relative role of repulsive and attractive interactions on the dynamics of scattering by isolated impurities and Anderson localization in disordered lattices. We find that weakly repulsive interactions increase the probability of tunneling through isolated impurities and decrease the localization in one-dimensional systems. The results for 1D lattices are obtained by direct diagonalization of the Hamiltonian. For 2D lattices, we employ an approach based on the recursive calculation of the Green's functions for two interacting particles. [Preview Abstract] |
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K1.00061: Designing an optical lattice trap for ions Matt Grau, Christoph Fischer, Oliver Wipfli, Jonathan Home Ions trapped in an optical lattice have the potential to realize interesting two and three-dimensional geometries with long range, tunable spin-spin couplings with application to quantum simulation of many-body spin Hamiltonians. We are constructing a new experiment to trap large numbers of ions at small ion-ion distances using a deep optical lattice in a high-finesse cavity. A MOT will act as a reservoir of neutral Magnesium atoms which will be loaded into the lattice, where the atom positions can be manipulated before resonant photoionization. Lattice spacing can be controlled by using an optical lattice at a second wavelength to create a spatially varying AC stark shift on a transition to an anti-trapped electronic state of the neutral atom. The lattice wavelength will be far detuned from the neutral and ion primary fluorescence transitions, which will result in low off-resonant scattering rates. Additionally, the optical lattice will be located in a cryo-cooled vacuum chamber to minimize the probability of collisions with background gas. We will report on the experimental progress of the MOT, high-finesse cavity, and optical trapping. [Preview Abstract] |
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K1.00062: Efficient calculation of localization properties of particles with long-range hopping in extended finite-sized lattices Joshua T Cantin, Roman V Krems Determining the localization properties of particles with long-range hopping in lattices larger than 100$^3$ via exact diagonalization is computationally prohibitive. A faster alternative is to use scaling arguments to qualitatively determine the location of the localization-diffusion crossover line as a function of system size. These scaling arguments are based on the delocalization mechanism: site-to-site resonances. The probability that a given site has a resonance with another site in the system is a monotonic function of the disorder strength, filling fraction, and lattice size. Thus, by identifying a specific probability with the localization-diffusion crossover line at small system sizes, one can efficiently extrapolate the crossover line to macroscopically large system sizes using a combination of numerical and analytical techniques. Here, we determine the quantitative accuracy of this new method by computing the dynamics of a particle with long-range hopping in 1D lattices with different sizes ranging over multiple orders of magnitude. We compare this method with one based on energy level statistics and investigate the connection between the probability of site-to-site resonances and the single-particle Green's function. [Preview Abstract] |
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K1.00063: Selfbound quantum droplets Tim Langen, Matthias Wenzel, Matthias Schmitt, Fabian Boettcher, Carl Buehner, Igor Ferrier-Barbut, Tilman Pfau Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report on the observation of such droplets using dysprosium atoms, with densities $10^8$ times lower than a helium droplet, in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. [Preview Abstract] |
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K1.00064: Cold interactions and chemical reactions of linear polyatomic anions with alkali-metal and alkaline-earth-metal atoms Michal Tomza We consider collisional studies of linear polyatomic ions immersed in ultracold atomic gases and investigate the intermolecular interactions and chemical reactions of several molecular anions (OH$^-$, CN$^-$, NCO$^-$, C$_2$H$^-$, C$_4$H$^-$) with alkali-metal (Li, Na, K, Rb, Cs) and alkaline-earth-metal (Mg, Ca, Sr, Ba) atoms. State-of-the-art \textit{ab initio} techniques are applied to compute the potential energy surfaces (PESs) for these systems. The coupled cluster method restricted to single, double, and noniterative triple excitations, CCSD(T), is employed and the scalar relativistic effects in heavier metal atoms are included within the small-core energy-consistent pseudopotentials. The leading long-range isotropic and anisotropic induction and dispersion interaction coefficients are obtained within the perturbation theory. The PESs are characterized in detail and their universal similarities typical for systems dominated by the induction interaction are discussed. The possible channels of chemical reactions and their control are analyzed based on the energetics of reactants. The present study of the electronic structure is the first step towards the evaluation of prospects for sympathetic cooling and controlled chemistry of linear polyatomic ions with ultracold atoms. [Preview Abstract] |
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K1.00065: Manifestations of dipolar collisions in thermal and BEC gases of dysprosium Yijun Tang, Andrew Sykes, Nathaniel Burdick, Dmitry S. Petrov, Benjamin Lev Ultracold and quantum gases of dysprosium provide the opportunity to explore the physics of strongly dipolar gases. In this talk, we report on two recent experiments that highlight this physics. The first is a direct measurement of collisions between two Bose-Einstein condensates with strong dipolar interactions. A collision halo corresponding to the two-body differential scattering cross section is observed. The results demonstrate a novel regime of quantum scattering, relevant to dipolar interactions, in which a large number of angular momentum states become coupled during the collision. We perform Monte-Carlo simulations to provide a detailed comparison between theoretical two-body cross sections and the experimental observations. The second is a measurement of the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy. We develop a theory to express the post-expansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases. [Preview Abstract] |
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K1.00066: A quantum gas microscope for highly dipolar atoms Susannah Dickerson, Anne Hebert, Aaron Krahn, Gregory Phelps, Markus Greiner Highly dipolar atoms present an exciting opportunity to extend previous quantum gas microscope (QGM) experiments to more complex systems influenced by long range, anisotropic interactions. Erbium, with its large dipole moment, numerous isotopes, and rich Feshbach spectrum, is an excellent element for such research. We present on current progress toward the construction of a QGM for ultracold erbium atoms in an optical lattice. We discuss technical features including the novel reflective imaging system and the optical lattice expandable in all three dimensions. We also discuss proposed avenues for research including studies of magnetism, the Einstein-de Haas effect, and quantum phase transitions with fractional filling factors. [Preview Abstract] |
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K1.00067: Retardation effects in induced atomic dipole-dipole interactions Sean Graham, Jeffrey McGuirk We present mean-field calculations of azimuthally averaged retarded dipole-dipole interactions in a Bose-Einstein condensate induced by a laser, at both long and short wavelengths. Our calculations demonstrate that dipole-dipole interactions become significantly stronger at shorter wavelengths, by as much as 30-fold, due to retardation effects. This enhancement, along with the inclusion of the dynamic polarizability, indicate a method of inducing long-range interatomic interactions in neutral atom condensates at significantly lower intensities than previously realized. [Preview Abstract] |
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K1.00068: Dipolar droplets in bosonic erbium quantum fluids. Lauriane Chomaz, Simon Baier, Daniel Petter, Giulia Faraoni, Jan-Hendrik Becher, Rick van Bijnen, Manfred J. Mark, Francesca Ferlaino Due to their large magnetic moment and exotic electronic configuration, atoms of the lanthanide family, such as dysprosium (Dy) and erbium (Er), are an ideal platform for exploring the competition between inter-particle interactions of different origins and behaviors. Recently, a novel phase of dilute droplet has been observed in an ultracold gas of bosonic Dy when changing the ratio of the contact and dipole-dipole interactions and setting the mean-field interactions to slightly attractive. This has been attributed to the distinct, non-vanishing, beyond-mean-field effects in dipolar gases when the mean interaction cancels. Here we report on the investigation of droplet physics in fluids of bosonic Er. By precise control of the scattering length $a$, we quantitatively probe the Bose-Einstein condensate (BEC)-to-droplet phase diagram and the rich underlying dynamics. In a prolate geometry, we observe a crossover from a BEC to a single macro-droplet, prove the stabilizing role of quantum fluctuations and characterize the special dynamical properties of the droplet. In an oblate geometry, we observe the formation of assemblies of tinier droplets arranged in a chain and explore the special state dynamics following a quench of $a$, marked by successive merging and reformation events. [Preview Abstract] |
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K1.00069: Thermodynamics and Magnetism of the Fermi-Hubbard Hamiltonian 2D-3D Crossover Rick Mukherjee, Thereza Paiva, Richard T. Scalettar, Randall G. Hulet, Kaden R. A. Hazzard To observe antiferromagnetism with fermionic ultracold atoms in optical lattices is one of the major ongoing pursuits in cold atoms. Atoms in anisotropic lattices are an interesting place to explore anti-ferromagnetic (AF) order in ultracold systems. We investigate the possibility of enhancing magnetic order by using anisotropy, specifically in a cubic lattice with tunneling stronger along two directions than in the third, which interpolates between the 2D and isotropic 3D regimes. Using determinantal Quantum Monte Carlo methods, we calculate the real space spin-spin correlations and the corresponding magnetic structure factor as a function of temperature and anisotropy for the model at half filling. Similar to the 1D-3D crossover, we find enhanced magnetic structure due to anisotropy for some interaction strengths. Although the long-ranged magnetic order never exceeds that of the isotropic system at the optimal interaction strength, the correlations become anisotropic, which can lead to enhanced short-ranged correlations along certain directions. [Preview Abstract] |
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K1.00070: COLD RYDBERG GASES AND PLASMAS |
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K1.00071: Probing inter-atomic correlations using excitation to high Rydberg states Jovica Stanojevic, Robin C\^ot\'e We study potential surfaces of a Rydberg atom interacting with several ground-state atoms of the same or different species than the Rydberg atom. The energy of the Rydberg atom depends measurably on the positions of the ground-state atoms and the Rydberg state. It has been demonstrated recently that these potentials support molecular bound states. Our goal is to utilize these potential surfaces for various $n\ell$ states as means to probe correlations between ground-state atoms. [Preview Abstract] |
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K1.00072: Measurement of $nD$ Rydberg-ground molecules in Rb Jamie MacLennan, Georg Raithel We experimentally measure the energies of several Rydberg-ground molecular bound states in Rb(nD + 5S$_{1/2}$), including vibrationally excited states. Because these molecular states arise from the scattering interaction of a Rydberg electron with a ground-state atom, their measurement allows an estimate of scattering lengths. Photoassociation out of an optical dipole trap facilitates our observation of molecules of relatively low principal quantum numbers, leading to good resolution of the bound-energy measurements. The study further addresses hyperfine-mixed singlet-triplet states. [Preview Abstract] |
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K1.00073: Adiabatic preparation of Rydberg crystals in a cold lattice gas: Influence of atomic relaxations David Petrosyan, Klaus Molmer, Michael Fleischhauer Strong, long-range interactions between atoms in high-lying Rydberg states make them attractive systems for the studies of ordered phases and phase transitions of interacting many-body systems. Different approaches have been explored, both theoretically and experimentally, for the preparation of crystalline order of Rydberg excitations in spatially-extended ensembles of cold atoms. These include direct (near-)resonant laser excitation of interacting Rydberg states in a lattice gas, and adiabatic preparation of crystalline phases of Rydberg excitations in a one-dimensional optical lattice by adiabatic frequency sweep of the excitation laser. We show, however, that taking into account realistic relaxation processes affecting the atoms severely complicates the prospects of attaining sizable crystals of Rydberg excitations in laser-driven atomic media. Our many-body simulations well reproduce the experimental observations [Schau{\ss} \textit{et al.}, Science \textbf{347}, 1455 (2015)] of spatial ordering of Rydberg excitations in driven dissipative lattice gases, as well as highly sub-Poissonian probability distribution of the excitation number. We find that the excitations essentially form liquid rather than crystal phases with long-range order. [Preview Abstract] |
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K1.00074: Effect of atomic motion on Rydberg blockade in a hot atomic beam S. Yoshida, J. Burgd\"orfer, X. Zhang, F. B. Dunning The dipole blockade of very-high-$n$ ($n \sim 300$) strontium $5snf$ $^1F_3$ Rydberg atoms in a hot atomic beam is studied. For such high $n$, the blockade radius ($\sim$ 0.1mm) can exceed the linear dimensions of the excitation volume. Rydberg atoms formed inside the excitation volume can, upon leaving the region, continue to suppress excitation until they have moved further away than the blockade radius. Moreover, the high density of states near the $F$-states originating from strong coupling to nearby high-$L$ states results in a small but finite probability for excitation of $n$ $^1F_3$ atom pairs at small internuclear separations below the blockade radius. We suggest a theoretical model to study the time evolution of the average Rydberg number and the Mandel $Q$ parameter revealing the correlation in many-body excitation in a time resolved manner. The results will be compared with measured data. [Preview Abstract] |
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K1.00075: Towards Rydberg dressing of a lithium Fermi gas Elmer Guardado-Sanchez, Peter Schauss, Debayan Mitra, Peter Brown, Waseem Bakr One attractive route towards finite-range interactions in ultracold gases is off-resonant coupling to Rydberg states, the so-called Rydberg dressing. Lithium is an interesting candidate due to its light mass and therefore fast dynamics. We report on the progress of Rydberg spectroscopy of lithium p-states with an ultra-violet laser at 230nm. We achieve narrow linewidth UV-light of up to 80mW by frequency-quadrupling of an amplified diode laser at 920nm locked to a ULE cavity. As a first step we implemented a V-type spectroscopy in a lithium cell and afterwards we plan to perform high-resolution loss spectroscopy in our quantum gas microscope setup. The long-term goal is a Fermi gas with tunable finite-range interactions under the microscope. [Preview Abstract] |
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K1.00076: Toward Probing Many-Body Correlations in Ultracold Gases using Ultralong-Range Rydberg Molecules J. D. Whalen, R. Ding, F. Camargo, F. B. Dunning, T. C. Killian Experimental techniques such as photoassociation spectroscopy and, more recently, quantum gas microscopes have been developed to probe correlations between atoms in ultracold quantum systems. These techniques have been remarkably successful at measuring correlations at very short ranges, $r <200 \,a_0$, and at ranges of the order of an optical lattice site, $r >5000\, a_0$. However, many physical systems such as halo dimers, Efimov trimers, Cooper pairs, etc. express correlations in a more intermediate regime. We propose a new method of probing this intermediate regime using photoassociation of ultralong-range Rydberg molecules. Excitation to well localized dimer states of varying principal quantum number ($20 < n < 100$) will provide a tunable probe of interparticle correlations and direct measurement of the two-body correlation function $g^{(2)}(r)$. We present an experimental proposal and preliminary results using this technique to measure the two-body wavefunction of a strongly interacting gas of $^{84}$Sr and $^{88}$Sr. [Preview Abstract] |
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K1.00077: Symmetry-protected collisions between strongly interacting photons Travis Nicholson, Jeff Thompson, Qiyu Liang, Sergio Cantu, Aditya Venkatramani, Soonwon Choi, Daniel Viscor, Thomas Pohl, Mikhail Lukin, Vladan Vuletic Realizing robust quantum phenomena in strongly interacting systems is one of the central challenges in modern physical science. Here, using coherent coupling between light and Rydberg excitations in an ultracold atomic gas, we demonstrate a controlled and coherent state exchange collision between two strongly interacting photons. The collision is accompanied by a $\pi/2$ phase shift, which is robust in that the value of the shift is determined by the interaction symmetry rather than the precise experimental parameters, and in that it occurs under conditions where photon absorption is minimal. The measured phase shift of $0.48(3)\pi$ is in excellent agreement with a theoretical model. These observations open a route to realizing robust single-photon switches and all-optical quantum logic gates, and to exploring novel quantum many-body phenomena with strongly interacting photons. [Preview Abstract] |
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K1.00078: Spatial and Temporal Correlations in a Cold-Atom Rydberg-EIT System Michael Viray, Stephanie Miller, Georg Raithel We investigate spatial and temporal second-order correlation functions, g\textasciicircum ((2) ) (r) and g\textasciicircum ((2) ) ($\tau )$, of cold rubidium-87 Rydberg atoms in a Rydberg-electromagnetically-induced-transparency (Rydberg-EIT) medium. To measure the spatial correlations, Rydberg atoms are field-ionized, and the resulting ion positions are recorded and processed to yield the spatial correlation function. For the temporal correlations in the Rydberg-EIT medium, the photon timing of the probe beam is recorded with a single photon counting module, and temporal correlations are extracted. We present preliminary results of these measurements and look at relations between the two correlation functions. [Preview Abstract] |
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K1.00079: Ultracold neutral plasma heating due to resonance excitation Adam Dodson, Quinton McKnight, Tucker Sprenkle, Scott Bergeson We report electron heating measurements in an expanding ultracold neutral calcium plasma. The plasma is formed by resonantly ionizing calcium atoms in a magneto-optical trap. The 397 nm resonance transition is excited at intensities ranging from 0.2 to 10 times the saturation intensity. We observe an increasing plasma expansion rate due to more rapid electron heating as the intensity of the 397 nm excitation increases. We discuss possible implications for laser-cooling the ions in this ultracold neutral plasma environment. [Preview Abstract] |
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K1.00080: Experimental optimization of directed field ionization Zhimin Cheryl Liu, Vincent C. Gregoric, Thomas J. Carroll, Michael W. Noel The state distribution of an ensemble of Rydberg atoms is commonly measured using selective field ionization. The resulting time resolved ionization signal from a single energy eigenstate tends to spread out due to the multiple avoided Stark level crossings atoms must traverse on the way to ionization. The shape of the ionization signal can be modified by adding a perturbation field to the main field ramp. Here, we present experimental results of the manipulation of the ionization signal using a genetic algorithm. We address how both the genetic algorithm and the experimental parameters were adjusted to achieve an optimized result. [Preview Abstract] |
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K1.00081: Directed Field Ionization: A Genetic Algorithm for Evolving Electric Field Pulses Xinyue Kang, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel When an ionizing electric field pulse is applied to a Rydberg atom, the electron's amplitude traverses many avoided crossings among the Stark levels as the field increases. The resulting superposition determines the shape of the time resolved field ionization spectrum at a detector. An engineered electric field pulse that sweeps back and forth through avoided crossings can control the phase evolution so as to determine the electron's path through the Stark map. In the region of $n=35$ in rubidium there are hundreds of potential avoided crossings; this yields a large space of possible pulses. We use a genetic algorithm to search this space and evolve electric field pulses to direct the ionization of the Rydberg electron in rubidium. We present the algorithm along with a comparison of simulated and experimental results. [Preview Abstract] |
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K1.00082: Blackbody effects in high-precision microwave spectroscopy with circular Rydberg atoms Stephen DiIorio, Andira Ramos, Kaitlin Moore, Georg Raithel Rydberg atoms experience a shift in transition frequencies and a shortening of lifetimes due to blackbody radiation (BBR). In a proposed Rydberg-constant measurement (RCM), which hopes to contribute to solving the ``proton radius puzzle'' [Bernauer, Pohl, Sci. Am. 310, 32 (2014)], circular Rydberg atoms are used. This work requires a careful examination of BBR effects. Typically, approximations are made to account for BBR effects, however, since BBR at room temperature matches the frequency range of our transitions, we follow the exact procedure outlined by Farley and Wing [Farley, Wing, Phys. Rev. A 23, 2397 (1981)] to calculate these shifts. We present calculations for BBR shifts in different temperature regimes and show that these calculated shifts converge and do not necessitate the consideration of continuum transitions. We also present calculated lifetimes of the relevant states in different temperature regimes. [Preview Abstract] |
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K1.00083: An ultracold potassium Rydberg source for experiments in quantum optics and many-body physics Charles Conover, Pamela DuPre, Ai Phuong Tong, Carlvin Sanon, Kevin Clarke, Brian Doolittle, Stephen Louria, Philip Adamson We report on the development of an apparatus for the study of quantum dynamics of Rydberg atoms of potassium. Samples of Rydberg atoms at 1 mK and varying density are excited in a magneto-optical trap of $10^7$ K-39 atoms. The atoms are excited to Rydberg states in a steps from 4s to 5p and from 5p to $ns$ and $nd$ states using stabilized external-cavity diode lasers at 405 nm and 980 nm. Selective field ionization and detection with microchannel plates provides a platform for spectroscopic measurements in potassium, exploration of multiphoton processes, and experiments on cold atom collisions. [Preview Abstract] |
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K1.00084: A Rydberg/cavity QED apparatus for exploring polariton blockade Alexandros Georgakopoulos, Albert Ryou, Ningyuan Jia, Nathan Schine, Ariel Sommer, Jonathan Simon In this work, we present the technical advances that have enabled us to explore Rydberg-mediated Interactions between resonator photons. In particular, we describe an exotic resonator geometry that enables us to maintain ~the small mode waist essential for exploring blockade physics, while keeping all material surfaces nearly a full cm away from the electric-field sensitive Rydbergs. We achieve stray fields stable at the 10mV/cm level over a day, in spite of the presence of a high-voltage piezo actuator to stabilize the resonator length to the few angstrom level. This enables us to employ 87Rb Rydbergs in the n$=$\textit121S quantum state, with a DC polarizability of nearly 24GHz/(v/cm)\textasciicircum 2, for our cavity Rydberg EIT experiments, thereby reaching the blockaded regime, indicating strong interactions between individual photons. We will also explore prospects for pushing these experiments into a multimode regime where dissipative manybody pumping will allow us to explore crystals and topological fluids of photons. [Preview Abstract] |
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K1.00085: DEGENERATE FERMI GASES |
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K1.00086: Towards ultracold mixtures of lithium and strontium atoms Xiaobin Ma, Zhuxiong Ye, Liyang Xie, Xiangliang Li, Li You, Meng Khoon Tey Both lithium and strontium come with bosonic and fermionic isotopes, which will enable many possibilities for rich inter-species interaction dominated mixture physics, and facilitate systematic investigations of impurity and disorder related many body quantum models. Progress towards a new experimental setup aimed at realizing degenerate mixtures of lithium and strontium atoms will be presented. [Preview Abstract] |
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K1.00087: Transport of ultracold atoms through a quantum point contact Samuel Häusler, Martin Lebrat, Dominik Husmann, Laura Corman, Sebastian Krinner, Charles Grenier, Jean-Philippe Brantut, Tilman Esslinger We explore transport of neutral particles through a quantum point contact with tunable interactions. The contact is optically imprinted onto the center of a cigar-shaped cloud of fermionic lithium 6 atoms connected to macroscopic reservoirs on each side. We create a particle, spin or temperature bias between the reservoirs and measure the induced conductance. At weak attractive interactions we observe quantized particle conductance at multiples of 1/h, an upper bound for Fermi liquid reservoirs. Upon increasing attraction the plateaus contineously increase to non-universal values as high as 4/h before the gas becomes superfluid. At stronger interactions, the plateaus in the particle conductance disappear while spin transport is suppressed, signaling the emergence of superfluid pairing. The anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the strongly attractive gas. Complementary to particle and spin transport we study the thermoelectric response to a temperature gradient between the reservoirs. We observe that resonant interactions strongly modify the particle and energy evolution compared to the weakly attractive case. [Preview Abstract] |
(Author Not Attending)
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K1.00088: New apparatus for the production of Fermi-Fermi mixtures of Dy and K Marian Kreyer, Cornelis Ravensbergen, Slava Tzanova, Elisa Soave, Alexander Werlberger, Vincent Corre, Emil Kirilov, Rudolf Grimm We have developed a new apparatus for the production of Fermi-Fermi mixtures of dysprosium and potassium. An atomic beam of dysprosium is produced in a high-temperature effusion oven and decelerated with a Zeeman slower. The atoms are then trapped by a narrow-line magneto-optical trap (MOT) operating on the 626\ nm intercombination transition. Potassium atoms are first trapped with a 2D$^+$ MOT, which produces a beam of slow atoms, and then transferred to the 3D MOT in the main chamber. We have so far achieved MOTs of bosonic $^{39}$K and $^{164}$Dy, and fermionic $^{40}$K and $^{161}$Dy, as well as the first double MOT of Dy and K. Our laser systems are based on infrared fiber lasers, which provide Dy light via sum frequency generation and K light via frequency-doubling, respectively. This brings the advantages of high stability, narrow linewidths and high beam quality, as well as the possibility to supply repumping light for potassium via sideband modulation. Further laser systems will enable narrow-line cooling for Dy as well as gray-molasses cooling for K. [Preview Abstract] |
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K1.00089: Interaction effects in two-dimensional Fermi gases S.L. Uppalapati, Daniel Sheehy Recent atomic physics experiments [1,2,3,4] have investigated two-dimensional fermionic atomic gases confined to a quasi two-dimensional trapping potential. Taking advantage of the fact that short-ranged attractive interactions are marginal in two-dimensions, we apply a renormalization group method to compute observable properties such as the local density, taking account of the harmonic trapping potential using the local density approximation. We compare our theoretical predictions to recent experimental data in the balanced and imbalanced regimes. [1] W. Ong et al, Phys. Rev. Lett. \textbf{114}, 110403 (2015) [2] K. Fenech et al, Phys. Rev. Lett. \textbf{116}, 045302 (2016) [3] I. Boettcher et al, Phys. Rev. Lett. \textbf{116}, 045303 (2016) [4] D. Mitra et al, Phys. Rev. Lett. \textbf{117}, 093601 (2016) [Preview Abstract] |
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K1.00090: Fermi Gas Microscopy of Potassium Fudong Wang, Rhys Anderson, Peihang Xu, Vijin Venu, Graham J. A. Edge, Stefan Trotzky, Joseph H. Thywissen Quantum gas microscopes offer a unique and direct view on strongly correlated atoms in optical lattices. Optical imaging with single-site resolution is a local probe, when the system size is large, and especially when motional states of atoms are restricted to the lowest band of the lattice. We present the current performance of our Fermi gas microscope imaging $^{40}$K atoms trapped in an optical lattice through a 200-micron-thick sapphire window. In-situ fluorescence imaging relies on continuous laser cooling to pin atoms to a single site during imaging. We have extended our original approach of electromagnetically-induced-transparency (EIT) cooling by combining it with simultaneous Raman sideband cooling (RSC). This method shows an improved performance over a ``pure’’ EIT cooling scheme. We describe the principle behind this method, show new images, and discuss measurements in progress. [Preview Abstract] |
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K1.00091: Probing and studying homogeneous atomic Fermi gases Zhenjie Yan, Biswaroop Mukherjee, Parth Patel, Airlia Shaffer-Moag, Cedric Wilson, Richard Fletcher, Zoran Hadzibabic, Tarik Yefsah, Julian Struck, Martin Zwierlein We create and study homogeneous Fermi gases of ultracold atoms in uniform trapping potentials. The homogeneity of the gas enables the measurement of momentum distributions without density averaging. For the non-interacting Fermi gas, we observe the emergence of the Fermi surface and the saturated occupation of one particle per momentum state. For thermodynamic measurements, we convert the uniform trap into a hybrid potential that is harmonic in one dimension and uniform in the other two. The spatially resolved compressibility reveals the superfluid transition in a spin-balanced Fermi gas, saturation in a fully polarized Fermi gas, and strong attraction in the polaronic regime of a partially polarized Fermi gas. In addition, we present results on the temperature dependence of the contact of the unitary Fermi gas measured with radio-frequency spectroscopy. [Preview Abstract] |
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K1.00092: QUANTUM INFORMATION |
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K1.00093: Towards quantum information transport through a classical conductor Da An, Hartmut Haeffner, Maya Lewin-Berlin, Erik Urban Establishing quantum links between separately trapped ions is a significant step towards scalable trapped ion quantum computation. Here, we present our design, simulation, and ongoing implementation of a novel surface ion trap for studying quantum correlations between separate trapping sights through an ordinary conducting wire. This is a challenging task since the thermal noise in the wire is much greater than the motional ion energy, but as long as the decoherence sources are minimized, we can achieve quantum coupling through the wire. We also include intermediate steps towards this goal, such as characterizing the stability of our novel trap, which has variable trapping height, and establishing a classical link through the wire. This technology may lead to quantum computation with mixed ion species, sympathetic cooling of ion species that cannot be co-trapped, and hybrid quantum devices that couple ion based qubits with superconducting qubits. [Preview Abstract] |
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K1.00094: DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number Dr. Sahadev Pradhan The flow over a 2D leading-edge flat plate is studied at Mach number \textit{Ma }$= (U_{inf}/ \backslash $\textit{sqrt\textbraceleft k}$_{B}T_{inf}$\textit{/ m\textbraceright ) }in the range \textit{\textless Ma \textless 10}, and at Reynolds number number \textit{Re }$= (L_{T} U_{inf}$\textit{ rho}$_{inf\thinspace }$\textit{)/ mu}$_{inf\thinspace }$ equal to 10$^{\mathrm{\thinspace \thinspace }}$using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number. Here, $L_{T}$is the characteristic dimension, $U_{inf}$and $T_{inf}$are the free stream velocity and temperature, \textit{rho}$_{inf}$ is the free stream density, $m$is the molecular mass, \textit{mu}$_{inf\thinspace }$is the molecular viscosity based on the free stream temperature $T_{inf},$and $k_{B}$is the Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip ((Pradhan and Kumaran, J. Fluid Mech-2011); (Kumaran and Pradhan, J. Fluid Mech-2014)) at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain. [Preview Abstract] |
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K1.00095: Investigating phonon-mediated interactions with polar molecules John Sous, Kirk Madison, Mona Berciu, Roman Krems We show that an ensemble of polar molecules in an optical lattice realizes the Peierls polaron model for hard-core particles/pseudospins. We analyze the quasiparticle spectrum in the one-particle subspace, the two-particle subspace and at finite concentrations. We derive an effective model that describes the low-energy behavior of the system. We show that the Hamiltonian includes phonon-mediated repulsions and phonon-mediated ``pair-hopping" terms which move the particle pair as a whole. We show that microwave excitations of the system exhibit signatures of these interactions. These results pave the way for the experimental observation of phonon-mediated repulsion. [Preview Abstract] |
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K1.00096: Simulation of Quantum Many-Body Dynamics for Generic Strongly-Interacting Systems Gregory Meyer, Francisco Machado, Norman Yao Recent experimental advances have enabled the bottom-up assembly of complex, strongly interacting quantum many-body systems from individual atoms, ions, molecules and photons. These advances open the door to studying dynamics in isolated quantum systems as well as the possibility of realizing novel out-of-equilibrium phases of matter. Numerical studies provide insight into these systems; however, computational time and memory usage limit common numerical methods such as exact diagonalization to relatively small Hilbert spaces of dimension $\sim2^{15}$. Here we present progress toward a new software package for dynamical time evolution of large generic quantum systems on massively parallel computing architectures. By projecting large sparse Hamiltonians into a much smaller Krylov subspace, we are able to compute the evolution of strongly interacting systems with Hilbert space dimension nearing $2^{30}$. We discuss and benchmark different design implementations, such as matrix-free methods and GPU based calculations, using both pre-thermal time crystals and the Sachdev-Ye-Kitaev model as examples. We also include a simple symbolic language to describe generic Hamiltonians, allowing simulation of diverse quantum systems without any modification of the underlying C and Fortran code. [Preview Abstract] |
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K1.00097: Quantum simulation using photons and room temperature atoms Connor Goham, Mehdi Namazi, Eden Figueroa Recent proposals show that Electromagnetically Induced Transparency (EIT) using quantized light fields and atoms can be a promising and alternative approach for quantum simulation [1,2]. In our experiment we generate a dark state polariton (DSP) through the storage of a pulse of light in a room temperature vapor and retrieve it using a multi-lambda scheme including the D1 and D2 lines of rubidium 87 atoms [3]. By applying a position dependent magnetic field during retrieval we have engineered the resultant coupled DSPs to follow a nonlinear Dirac Hamiltonian analog to the Jackiw-Rebbi model describing a Dirac field with spatially variable mass. [1] Scientific Reports, 4:6110 2014. [2] Phys. Rev. Lett., 105:173603 2010. [3] Nature Communications, 5:5542 2014. [Preview Abstract] |
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K1.00098: A Raman phase gate for $^{87}$Rb Bose--Einstein Condensates Joseph D. Murphree, Maitreyi Jayaseelan, Justin T. Schultz, Nicholas P. Bigelow Bose--Einstein condensates (BECs) are of interest for use in quantum information and quantum computing due to their macroscopic dimensions and long coherence lifetimes. This requires the realization of quantum gates in BECs, and phase gates are an important first step. We use a coherent Raman process to implement a phase gate on a $^{87}$Rb BEC. This process is capable of effecting a spatially varying, arbitrary rotation on the Bloch sphere in the pseudo-spin-$\frac{1}{2}$ space created from two spin sublevels. We first use a set of Raman pulses to create a full-Bloch BEC, a spin texture on the cloud which includes every state on the Bloch sphere. A second set of Raman pulses introduces a phase shift between the spin components, applying a phase gate to every possible superposition of states simultaneously. The amount and spatial uniformity of the added phase is then measured using atom-optic polarimetry. Using structured or singular Raman beams with this technique could enable the study of quantum gates with Laguerre--Gaussian basis states. [Preview Abstract] |
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K1.00099: A Multimode Analysis of an Atom-Cavity System as a Controlled Phase Gate William Konyk, Julio Gea-Banacloche We study the scattering of a single- and two-photon pulse off of a three-level atom in the V configuration contained within a cavity. Our solution utilizes a full multimode treatment of the quantized electric field and leads to analytic results for common input pulses. We use this solution to analyze the system's ability to act as a conditional phase gate between two photons for various choices of couplings and detunings. We find that the maximum success probability is nearly identical to that obtained for a similar atom in a chiral waveguide configuration. We also show that the initial pulse shape has a significant effect on the gate operation, in some cases entirely preventing the ideal $\pi$ phase shift between the two photons for any choice of parameters. [Preview Abstract] |
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K1.00100: Analytical results for a conditional phase shift between single-photon pulses in a nonlocal nonlinear medium Balakrishnan Viswanathan, Julio Gea-Banacloche We analyze a recent scheme proposed by Xia et al.\footnote{K. Xia, M. Johnsson, P. L. Knight, and J. Twamley, Phys. Rev. Lett. {\bf 116}, 023601 (2016)} to induce a conditional phase shift between two single-photon pulses by having them propagate at different speeds through a nonlinear medium with a nonlocal response. We have obtained an analytical solution for the case they considered, which supports their claim that a $\pi$ phase shift with unit fidelity is possible in principle. We discuss the conditions that have to be met and the challenges and opportunities that this might present to the realization of a single-photon conditional phase gate. [Preview Abstract] |
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K1.00101: A high performance microfabricated surface ion trap Daniel Lobser, Matthew Blain, Raymond Haltli, Andrew Hollowell, Melissa Revelle, Daniel Stick, Christopher Yale, Peter Maunz Microfabricated surface ion traps present a natural solution to the problem of scalability in trapped ion quantum computing architectures. We address some of the chief concerns about surface ion traps by demonstrating low heating rates, long trapping times as well as other high-performance features of Sandia's high optical access (HOA-2) trap. For example, due to the HOA's specific electrode layout, we are able to rotate principal axes of the trapping potential from 0 to 2$\pi $ without any change in the secular trap frequencies. We have also achieved the first single-qubit gates with a diamond norm below a rigorous fault tolerance threshold [1,2], and a two-qubit M{\o}lmer-S{\o}rensen gate [3] with a process fidelity of 99.58(6). Here we present specific details of trap capabilities, such as shuttling and ion reordering, as well as details of our high fidelity single- and two-qubit gates. ~ [1] R. Blume-Kohout et al. arXiv:1606.07674. [2] P. Aliferis and J. Preskill, Phys. Rev. A 79, 012332 (2009). [3] A. S{\o}rensen and K. M{\o}lmer, Phys. Rev. Lett. 82, 1971 (1999) [Preview Abstract] |
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K1.00102: $^{\mathrm{133}}$Ba$^{\mathrm{+}}$: a new ion qubit. Justin Christensen, David Hucul, Wesley Campbell, Eric Hudson $^{\mathrm{133}}$Ba$^{\mathrm{+}}$ combines many of the advantages of commonly used trapped ion qubits. $^{\mathrm{133}}$Ba$^{\mathrm{+}}$ has a nuclear spin 1/2, allowing for a robust hyperfine qubit with simple state preparation and readout. The existence of long-lived metastable D-states and a lack of low-lying F-states simplifies shelving, which will allow high fidelity state detection. The visible wavelength optical transitions enable the use of high-power lasers, low-loss fibers, high quantum efficiency detectors, and other optical technologies developed for visible wavelength light. Furthermore, background-free qubit readout, where the readout is insensitive to laser scatter, is possible in $^{\mathrm{133}}$Ba$^{\mathrm{+}}$, and simplifies its use in small ion traps and the study of ions near surfaces. We report progress on realizing this qubit. We load barium ions into an ion trap using thermal ionization from a platinum ribbon. We experimentally demonstrate the isotopic purification of large numbers of barium ions using laser heating and cooling along with mass filtering to produce isotopically pure chains of any naturally-occurring barium isotope. This purification process has allowed us to laser cool rare, naturally-occurring barium isotopes $^{\mathrm{132}}$Ba$^{\mathrm{+}}$ and $^{\mathrm{130}}$Ba$^{\mathrm{+}}$, and we report the isotope shifts from $^{\mathrm{138}}$Ba$^{\mathrm{+}}$ of the P$_{\mathrm{1/2}}$ to D$_{\mathrm{3/2\thinspace }}$transitions near 650 nm for the first time. In addition, we have developed an ion gun to produce high luminosity ion beams with adjustable mean kinetic energy by combining a surface ionization source and ion optics. [Preview Abstract] |
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K1.00103: Nondestructive fluorescence detection of hyperfine states of Rb using an EMCCD camera Minho Kwon, Matthew Ebert, Christopher Young, Thad Walker, Mark Saffman We demonstrate a method to non-destructively differentiate two hyperfine ground states of trapped neutral ${}^{87}$ Rb atoms, with an EMCCD camera. The semi-closed cycling transition limits the number of photons that atoms can scatter before their internal state changes. We utilize circularly polarized probe light and strictly controlled quantization axis to fully close the transition. This enables us to collect sufficient photons for a measurement while preserving the internal state. In our proof of principle experiments up to five trap sites are interrogated in parallel. A few ms of readout time and scalability of the method allow significant speed ups in quantum information experiments with neutral atoms. We also report progress toward Rydberg-mediated gate experiments using ensembles. [Preview Abstract] |
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K1.00104: Absolute Calibration of Analog Photodiodes with Correlated Twin Beams from Four-wave Mixing Meng-Chang Wu, Brian Anderson, Bonnie Schmittberger, Alan Migdall, Paul Lett Quantum-correlated twin beams are a promising source for absolute calibration of analog photodiodes over a large frequency range. In our experiment, we make two-mode squeezed light with four-wave mixing in a double-lambda scheme in a warm Rb vapor. At least -5 dB of intensity-difference squeezing in the measurement frequencies range of 100Hz to a few megahertz is obtained routinely. One of the correlated twin beams is detected by a first uncalibrated detector and this provides a reference for signals at a second uncalibrated detector. Fluctuations in one detector should be mirrored in the other, and any inefficiency of the photodiodes, or losses in the optical path for the twin beams will reduce the degree of their correlation. We can obtain the quantum efficiency of both analog photodiodes in the test by measuring the correlation functions of twin beams and having good loss measurements for all of the optical paths. We measure the losses of every optical element and the loss from the Rb atoms in the source. The main contributions to the uncertainties of the calibration are from the loss measurements. [Preview Abstract] |
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K1.00105: Visible-Wavelength Multi-Species Trapped-Ion Quantum Logic Colin Bruzewicz, Robert McConnell, Jonathon Sedlacek, Jules Stuart, John Chiaverini, Jeremy Sage Large-scale quantum information processing using trapped ions will likely utilize multiple atomic species to permit sympathetic cooling of shared ion motion and to facilitate quantum state measurement without decohering unmeasured qubits. Using the techniques of quantum logic spectroscopy, we demonstrate state transfer and subsequent readout using a memory (Ca$^{+}$) and auxiliary (Sr$^{+}$) ion in a surface-electrode ion trap. This method obviates the need for fluorescence detection of the memory ion, massively reducing the amount of resonant scattered light as a source of decoherence in other nearby memory ions. Further, the necessary lasers for manipulation of Ca$^{+}$ and Sr$^{+}$ are all in the visible and near-infrared portion of the spectrum and may permit the use of integrated photonic waveguides to route light throughout a trap array without the need for free-space optics. [Preview Abstract] |
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K1.00106: Implementation of a Single-Shot Displacement Receiver for Quaternary Phase-Shift-Keyed Coherent States Matthew DiMario, Francisco Becerra, Richard Jackson, Zeke Carrasco Non-Gaussian receivers that achieve discrimination errors below the Quantum Noise Limit (QNL) are an important tool in communication and quantum information. Discrimination of coherent states of light with zero probability of error is fundamentally impossible due to their intrinsic overlap. Therefore, the goal is to design and demonstrate strategies that minimize the probability of error and outperform a perfect heterodyne measurement working at the QNL, while being compatible with current communication technologies. We experimentally implement a strategy proposed in PRA 86, 042328 (2012) to discriminate between quaternary phase-shift keyed (QPSK) coherent states below the QNL that is based on simultaneously testing multiple hypotheses within a single-shot measurement. The receiver uses displacement operations and single photon counting without the need for any feedback operations and thus it is compatible with current high-bandwidth communications. In our demonstration we use optimized displacement operations to minimize the probability of error in a polarization based set-up. Our investigations allow us to identify how the critical parameters, such as visibility of the displacements and detection efficiency, influence the error probability as well as what is required to out-perform a heterodyne measurement under realistic noise and loss. [Preview Abstract] |
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K1.00107: Improvement in T2* via Cancellation of Spin Bath Induced Dephasing in Solid-State Spins Erik Bauch, Connor Hart, Jennifer Schloss, Matthew Turner, John Barry, Ronald L. Walsworth In measurements using ensembles of nitrogen vacancy (NV) centers in diamond, the magnetic field sensitivity can be improved by increasing the NV spin dephasing time, T2*. For NV ensembles, T2* is limited by dephasing arising from variations in the local environment sensed by individual NVs, such as applied magnetic fields, noise induced by other nearby spins, and strain. Here, we describe a systematic study of parameters influencing the NV ensemble T2*, and efforts to mitigate sources of inhomogeneity with demonstrated T2* improvements exceeding one order of magnitude. [Preview Abstract] |
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K1.00108: Linear optical quantum metrology with single photons -- Experimental errors, resource counting, and quantum Cram\'{e}r-Rau bounds Nicholas Studer, Jonathan Olson, Keith Motes, Patrick Birchall, Margarite LaBorde, Todd Moulder, Peter Rohde, Jonathan Dowling Quantum number-path entanglement is a resource for super-sensitive quantum metrology and in particular provides for sub-shotnoise or even Heisenberg-limited sensitivity. However, such number-path entanglement has thought to have been resource intensive to create in the first place -- typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feed-forward, which are difficult to implement. Recently we showed that number-path entanglement from a BOSONSAMPLING inspired interferometer can be used to beat the shot-noise limit. In this work, we compare and contrast different interferometric schemes, discuss resource counting, calculate exact quantum Cramer-Rao bounds, and study details of experimental errors. [Preview Abstract] |
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K1.00109: Towards a quantum network of room temperature quantum devices bertus jordaan, reihaneh shahrokhshahi, mehdi namazi, connor goham, eden figueroa Progressing quantum technologies to room temperature operation is key to unlock the potential and economical viability of novel many-device architectures. Along these lines, warm vapor alleviates the need for laser trapping and cooling in vacuum or cooling to cryogenic temperatures. Here we report our progress towards building a prototypical quantum network, containing several high duty cycle room-temperature quantum memories interconnected using high rate single photon sources [1,2]. We have already demonstrated important capabilities, such as memory-built photon-shaping techniques [3], compatibility with BB84-like quantum communication links [4], and the possibility of interfacing with low bandwidth (MHz range), cavity enhanced, SPDC-based photon source tuned to the Rb transitions. This body of works suggest that an elementary quantum network of room temperature devices is already within experimental reach. [1] M. Namazi, arXiv:1512.07374 (2015). [2] C. Kupchak, , Scientific Reports 5, 7658 (2015). [3] M. Namazi, Phys. Rev. A 92, 033846 (2015). [4] M. Namazi, arXiv 1609.08676 (2016). [Preview Abstract] |
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K1.00110: QUANTUM/COHERENT CONTROL |
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K1.00111: Preparation of Vibrationally Excited H$_{\mathrm{2}}$ in a Coherent Superposition of $M$-States Using Stark Induced Adiabatic Raman Passage (SARP) Nandini Mukherjee, Wenrui Dong, William Perreault, Richard Zare We prepare a large ensemble of rovibrationally excited ($v=$1, $J=$2) H$_{\mathrm{2}}$ molecules in a coherent superposition of $M$-states using Stark-induced adiabatic Raman passage (SARP) with linearly polarized single mode pump (532 nm) and Stokes (699 nm) laser pulses of duration 6 ns and 4 ns. A biaxial superposition state, \textbar $\psi $\textgreater $=$1/$\surd $2 [ \textbar $v=$1, $J=$2, $M=$-2\textgreater - \textbar $v=$1, $J=$2, $M=+$2\textgreater ], is prepared using SARP with a sequence of a pump laser pulse partially overlapping with a cross polarized Stokes laser pulse co-propagating along the quantization z-axis. The degree of phase coherence is measured by recording interference fringes in the ion signal produced using the O(2) line of 2$+$1 resonance enhanced multiphoton ionization (REMPI) from the rovibrationally excited ($v=$1,$ J=$2) level as a function of REMPI laser polarization angle. The ion signal is measured using a time-of-flight mass spectrometer. Nearly 60{\%} population transfer from H$_{\mathrm{2}}$ ($v=$0,$ J=$0) ground state to the superposition state in H$_{\mathrm{2}}$ ($v=$1, $J=$2) is measured from the depletion of Q(0) REMPI signal of the ($v=$0,$ J=$0) ground state. The $M$-state superposition behaves much like a multi-slit interferometer where the number of slits, i.e. the number of $M$-states, and their separations, i.e. the relative phase, can be varied experimentally. [Preview Abstract] |
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K1.00112: Raman transition at motional sideband for a trapped ion using co-propagating pulsed lasers and a high NA lens Yeong-Dae Kwon, Seokjun Hong, Minjae Lee, Dongil Dan Cho, Taehyun Kim A pulsed laser is a great tool for coherent control of qubits based on trapped ions. Unlike microwave, it allows addressing individual ions among the string of ions stored in the same trap, and the high instantaneous power of the pulsed laser enables faster and more stable qubit operations [1]. The pulsed laser can also play a crucial role in the cooling process, as two-photon Raman process allows transitions between different motional states of an ion, which makes the sideband cooling possible [2]. Generally, however, for such a transition to occur, two beams traveling in different directions are needed to impart a sufficient momentum kick to the ion. In this research, we show that co-propagating pulsed lasers are also capable of driving such inter-motional-state transitions as long as they reach the ion through a high NA lens, from which the beams gain the extra momentum difference. Such a scheme can vastly simplify the optical setup, since the active matching and stabilization of the path lengths of the two pulsed lasers are no longer required when the lasers co-propagate. [1] D. Hayes et al., Phys. Rev. Lett. 104, 140501 (2010). [2] C. Monroe et al., Phys. Rev. Lett. 75, 4011 (1995). [Preview Abstract] |
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K1.00113: Electron spin control and spin-libration coupling of a levitated nanodiamond Thai Hoang, Yue Ma, Jonghoon Ahn, Jaehoon Bang, Francis Robicheaux, Ming Gong, Zhang-qi Yin, Tongcang Li Hybrid spin-mechanical systems have great potentials in sensing, macroscopic quantum mechanics, and quantum information science. Recently, we optically levitated a nanodiamond and demonstrated electron spin control of its built-in nitrogen-vacancy (NV) centers in vacuum. We also observed the libration (torsional vibration) of a nanodiamond trapped by a linearly polarized laser beam in vacuum. We propose to achieve strong coupling between the electron spin of a NV center and the libration of a levitated nanodiamond with a uniform magnetic field. With a uniform magnetic field, multiple spins can couple to the torsional vibration at the same time. We propose to use this strong coupling to realize the Lipkin-Meshkov-Glick (LMG) model and generate rotational superposition states. [Preview Abstract] |
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K1.00114: Analysis of decoherence mechanisms in a single-atom quantum memory Matthias Koerber, Stefan Langenfeld, Olivier Morin, Andreas Neuzner, Stephan Ritter, Gerhard Rempe While photons are ideal for the transmission of quantum information, they require dedicated memories for long-term storage. The challenge for such a photonic quantum memory is the combination of an efficient light-matter interface with a low-decoherence encoding. To increase the time before the quantum information is lost, a thorough analysis of the relevant decoherence mechanisms is indispensable. Our optical quantum memory consists of a single rubidium atom trapped in a two dimensional optical lattice in a high-finesse Fabry-Perot-type optical resonator. The qubit is initially stored in a superposition of Zeeman states, making magnetic field fluctuations the dominant source of decoherence. The impact to this type of noise is greatly reduced by transferring the qubit into a subspace less susceptible to magnetic field fluctuations. In this configuration, the achievable coherence times are no longer limited by those fluctuations, but decoherence mechanisms induced by the trapping beams pose a new limit. We will discuss the origin and magnitude of the relevant effects and strategies for possible resolutions. [Preview Abstract] |
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K1.00115: Decoherence and electric field noise analysis of nitrogen vacancy center diamonds due to the surface charge fluctuations and lattice strain Deborah Santamore We theoretically investigate the decoherence mechanisms due to the electric field noise in nitrogen vacancy (NV) center diamonds. The noise is caused by both the surface charge fluctuations and strain due to surface contaminants and bulk impurities. The system is modeled with nitrogen impurities in diamond and hydrogen surface terminations with water. We obtain the equations of motion, calculate the electric field fluctuations, and analyze noise. We find that the surface effect is greater than lattice distortion by the bulk impurity substitution. We also discuss how to minimize the noise. Finally, we examine lattice distortion and stability of NV centers under high pressure. [Preview Abstract] |
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K1.00116: Manipulating trapped ions with ultrafast laser pulses to generate mesoscopic states and entanglement Steven Moses, David Wong-Campos, Kale Johnson, Jonathan Mizrahi, Christopher Monroe The main requirements for a viable quantum computing platform include robustness to external perturbations and logical operations faster than the system's decoherence time. Trapped ions have met these requirements while maintaining high operation fidelities. Although extensive work has been done in the resolved sideband regime, ultrafast quantum state control promises an improvement to both clock speeds and scalability. Here we demonstrate the use of ultrafast laser pulses for generating high fidelity spin-dependent momentum kicks (SDKs) in $^{171}$Yb$^+$ ions. These SDKs are the building blocks used to create mesoscopic superpositions, or Schr\"{o}dinger cat states, of motional states that enable sensing of thermal states up to room temperature. More recently, we have used a sequence of SDKs on two ions to realize a novel phase gate, which operates independent of temperature and is scalable to large system sizes. [Preview Abstract] |
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K1.00117: Quantum many-body control beyond the adiabatic regime Yogesh S Patil, Hil F H Cheung, Aditya G Date, Mukund Vengalattore We demonstrate the optomechanical realization of a non-equilibrium heat engine in a system out-of-equilibrium with its environment. We investigate the limits on the work-extraction efficiency in such non-equilibrium systems which violate adiabaticity or indeed even the fluctuation-dissipation theorem. We discuss how such protocols can potentially be used to relate microscopic non-equilibrium equalities to macroscopic thermodynamic quantities and to shed light on the microscopic basis of thermodynamics. Furthermore, we describe how feedback and continuous measurements can be used to coax out-of-equilibrium quantum systems into novel correlated many-body quantum states. As an example of the power of such non-equilibrium processes, we demonstrate a dramatic increase in the squeezing achieved using a non-equilibrium transient protocol. [Preview Abstract] |
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K1.00118: Atomic excitation probability for Fock and coherent-state pulses: asymptotic results Hemlin Swaran Rag, Julio Gea-Banacloche For a two-level atom in a cavity or waveguide, interacting with a single-photon pulse, the excitation probability $P_e$ can never equal one unless the pulse shape is the exact time-reverse of the spontaneous decay. For pulses with the ``wrong'' shape, we investigate (following the work of Wang et al.\footnote{Y. Wang, J. Min\'{a}\v{r}, and V. Scarani, Phys. Rev. A {\bf 86}, 023811 (2012)}) how many photons it takes to bring the excitation probability close to 1. For square pulses we find analytically that for large average photon numbers $\bar n$, $P_e-1$ scales as $1/\sqrt{\bar n}$, with a coefficient that is the same for Fock states as for coherent states. We also present analytical and numerical results for how the presence of additional losses affects $P_e$ and makes it necessary to increase the number of photons, even for the optimal-shape pulse. [Preview Abstract] |
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K1.00119: Two qubit gate operation using the frequency encoding technique Junghyun Lee, Keigo Arai, Huiliang Zhang, Erik Bauch, Emma Rosenfeld, Ronald Walsworth Nitrogen-vacancy (NV) color centers in diamond are good candidates for realizing a scalable spin coupled system. For a simple two NV electronic spin interacting system, two qubit gate operations can be realized through the spin dipolar interaction. With two NV electronic spins separated by about 10 nm, and by manipulating an applied magnetic field gradient and a Rabi driving field, we outline how the spin dipolar interaction can be controlled to create different types of two qubit gate operations. Furthermore, we outlook how this two electronic spin qubit system can act as a channel for entangling two nitrogen nuclear spins adjacent to each NV electronic spins. [Preview Abstract] |
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K1.00120: Are strategies in physics discrete? A remote controlled investigation Robert Heck, Jacob F. Sherson In science, strategies are formulated based on observations, calculations, or physical insight. For any given physical process, often several distinct strategies are identified. Are these truly distinct or simply low dimensional representations of a high dimensional continuum of solutions? Our online citizen science platform www.scienceathome.org used by more than 150,000 people recently enabled finding solutions to fast, 1D single atom transport [Nature2016]. Surprisingly, player trajectories bunched into discrete solution strategies (clans) yielding clear, distinct physical insight. Introducing the multi-dimensional vector in the direction of other local maxima we locate narrow, high-yield ``bridges'' connecting the clans. This demonstrates for this problem that a continuum of solutions with no clear physical interpretation does in fact exist. Next, four distinct strategies for creating Bose-Einstein condensates were investigated experimentally: hybrid and crossed dipole trap configurations in combination with either large volume or dimple loading from a magnetic trap. We find that although each conventional strategy appears locally optimal, ``bridges'' can be identified. In a novel approach, the problem was gamified allowing 750 citizen scientists to contribute to the experimental optimization yielding nearly a factor two improvement in atom number. [Preview Abstract] |
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K1.00121: Toward Nanoscale Magnetometry of Van der Waals Heterostructures using Nitrogen-Vacancy Centers in Diamond Thomas Mittiga, Satcher Hsieh, Chong Zu, Chenhao Jin, Jonghwan Kim, Bryce Kobrin, Feng Wang, Norman Yao Two-dimensional layered heterostructures remain at the forefront of materials research and are promising candidates from the perspective of both fundamental science and technological advancement. They can exhibit a rich array of magnetic phenomena, with recent experiments in transition metal dichalcogenides (TMD) demonstrating long-lived spin relaxation and coherence times. We present first steps toward a wide-field confocal microscope aimed at probing the exciton and defect-based magnetism of such materials. By observing the quenching of fluorescence from single Nitrogen-Vacancy centers of predetermined depths, we measure the transition dipole moment of the TMD and characterize this as a function of layer number. We also describe recent progress toward the imaging of magnetic defects and evaluate the feasibility of using this scheme to probe coupled spin and valley dynamics.~ [Preview Abstract] |
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K1.00122: Synthetic clock states generated in a Bose-Einstein condensate via continuous dynamical decoupling Nathan Lundblad, Dimitrios Trypogeorgos, Ana Valdes-Curiel, Erin Marshall, Ian Spielman Radiofrequency- or microwave-dressed states have been used in NV center and ion-trap experiments to extend coherence times, shielding qubits from magnetic field noise through a process known as continuous dynamical decoupling (1). Such field-insensitive dressed states, as applied in the context of ultracold neutral atoms, have applications related to the creation of novel phases of spin-orbit-coupled quantum matter (2). We present observations of such a protected dressed-state system in a Bose-Einstein condensate, including measurements of the dependence of the protection on rf coupling strength, and estimates of residual field sensitivities. \\ (1) Rabl, P. et al. Strong magnetic coupling between an electronic spin qubit and a mechanical resonator. Phys.~Rev.~B 79, 041302 (2009). \\ (2) Campbell, D.~L. \& Spielman, I.~B. Rashba realization: Raman with RF. New J. Phys. 18, 033035 (2016). [Preview Abstract] |
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K1.00123: NONLINEAR OPTICS |
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K1.00124: ABSTRACT WITHDRAWN |
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K1.00125: Rotational Doppler effect in third-harmonic generation from spinning molecules Ilya Sh. Averbukh, J. Zyss, A. Milner, V. Milner, E. Prost, E. Hertz, F. Billard, B. Lavorel, O. Faucher The angular Doppler effect results from interaction of a rotating body with a circularly-polarized (CP) light. In linear optics, it was first evidenced by observing the frequency shift imparted to a CP light transmitted through a mechanically rotated wave plate [Opt. Commun., {\bf 31}, 1 (1979)], and more recently, demonstrated in our experiments with fast spinning molecules [Nat Photon. {\bf 7}, 711 (2013); Phys.Rev.Lett. {\bf 112}, 113004 (2014); Phys.Rev.Lett. {\bf 114}, 103001 (2015)]. We present here the first observation of the nonlinear rotational Doppler shift in the frequency of optical harmonic generated in fast rotating molecules. Conservation of energy and angular momentum in the light-molecule interaction suggests four different kinds of nonlinear shifts depending on the mutual handedness of the circularly polarized fundamental and harmonic fields, as well as the handedness of the molecular rotation. All four types of the frequency shifts were observed in our experiments on third-harmonic generation in a gas of fast spinning $O_2$ molecules [Phys. Rev. A {\bf 94}, 051402(R) (2016)]. [Preview Abstract] |
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K1.00126: Rotational cavity optomechanics Wyatt Wetzel, B. Rodenburg, B. Ek, A. K. Jha, M. Bhattacharya We consider optomechanics based on the exchange of orbital angular momentum between light and matter. Specifically we consider a nanoparticle levitated in an optical ring trap in a cavity. The motion of this particle is probed by an angular lattice created by two co-propagating beams carrying equal but opposite angular momenta. Firstwe consider the case where the lattice is weak, so the nanoparticle can execute complete rotations about the cavity axis. We establishanalytically the existence of a linear regime where accurate Doppler velocimetry can be performed on the nanoparticle, and also describe numerically the dynamics in the nonlinear regime where the velocimetry is no longer accurate. Second, we consider the case where the lattice is strong and the nanoparticle executes torsional motion about the cavity axis. We find the presence of an external torque introduces an instability, but can also be used to tune continuously the linear optomechanical coupling whose strength can be measured by homodyning the cavity output field. This research was supported by the National Science Foundation (NSF) (1454931), the Office of Naval Research (N00014-14-1-0803), and the Research Corporation for Science Advancement (20966). [Preview Abstract] |
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K1.00127: Electromagnetically Induced Transparency in a Double-Lambda System Saesun Kim, Alberto Marino Electromagnetically induced transparency (EIT) is a well-known phenomenon due in part to its application to quantum devices such as quantum memory and quantum gates. Commonly, EIT is modeled with a three-level lambda configurations due to the simplicity of the calculation; however, all of the D1 transitions in Alkali atoms have four hyperfine levels. As a result, it is necessary to consider the effect of two excited states whose frequency separation is smaller or of the order of the Doppler broadening when working with atomic vapors. We model the atomic system as a double-lambda system and analytically calculate its response using the density matrix formalism under the assumption of a weak probe field and taking Doppler broadening into account. We show that the presence of the fourth level leads to an additional term in the susceptibility compared to two independent three-level lambda systems. This extra interference term leads to an enhancement of EIT and electromagnetically induced absorption (EIA) and under certain conditions to an additional absorption in-between the two upper levels. Finally, we measure the transmission spectrum through a $^{85}$Rb vapor cell and show that it agrees with the theoretical calculations. [Preview Abstract] |
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K1.00128: Harmonic generation with an ultra-strongly coupled cavity polariton Michael Crescimanno, Kenneth Singer, Bin Liu, Michael McMaster The large dipole density in a new class of glassy organic dyes results in ultrastrong exciton-cavity field coupling leading to polariton splittings of over an eV. We describe the theoretical model and experimental protocol used to understand third harmonic generation (THG) in this system. We quantify the THG enhancement at the polariton branches through its dependence on coupling, cavity-exciton detuning and cavity finesse. [Preview Abstract] |
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K1.00129: Current studies and improvements on a single frequency blue source generated by second harmonic from IR Ali Khademian, Sai Lakshman Jampani, Matthew Truscott, Anooja Jayaraj, David Shiner We have reported 81.5{\%} efficiency in generating \textasciitilde 500 mW of blue at 486 nm by second harmonic generation (SHG) from the IR, using a periodically poled Lithium Tantalate (PPSLT) crystal. Initially a total cavity loss of 0.65{\%} was observed. We developed techniques for careful measurement of individual losses such as scattering and absorption in the crystal and mirrors, polarization misalignment caused by the crystal and back reflection from the periodically poled boundaries of crystal. We have replaced the crystal with a tilted periodically poled crystal. This eliminated the reflection loss, but scattering in the crystal, we speculate from the MgO doping, is still causing enough feedback to destabilize the IR source. We are also replacing cavity mirrors with ultra-low loss sputtered mirrors to minimize their contribution to loss. Crystal lifetime at different blue power levels is being investigated. In our setup a mixed signal processer (MSP) is used for cavity locking and temperature stabilizing. Once MSP is programed by a computer interface, it can be installed inside the cavity housing, making the laser source standalone and self-sufficient. We have been able to stabilize and lock the laser cavity length, the temperature of the IR laser source, the temperature of fiber Bragg grating (FBG), and the temperature of the nonlinear crystal using the MSP, matching the performance of high end commercial temperature controllers and lock-in amplifiers. Our recent progress and improvements will be presented. [Preview Abstract] |
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K1.00130: ULTRA FAST |
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K1.00131: A superradiant laser integrated in a hollow-core photonic-crystal fiber Fereshteh Rajabi, Taehyun Yoon, Jeremy Flannery, Sreesh Venuturumilli, Michal Bajcsy Superradiant lasers exhibit a high spectral purity characterized by a frequency linewidth thousand times less than that of a conventional laser. This characteristic of superradiant laser, which is due to collective effects arising in the dipole ensemble forming the gain medium, makes it an exellent candidate for high-precision metrology applications. Additionally, superradiant lasers are an interesting platform to study strongly-correlated systems. We propose a fiber-integrated superradiant laser consisting of an ensemble of cold Cs atoms coupled to a single mode of radiation field in a Fabry-Perot cavity formed in a hollow-core photonic crystal fiber (HCPCF). The Cs atoms, initially cooled using a magneto-optical trap (MOT), are guided and confined inside a short piece of HCPCF with a magic-wavelength dipole trap. The Fabry-Perot cavity is integrated into the fiber using photonic-crystal slabs acting as mirrors, which are attached to the ends of the fiber piece. A small number of photons can synchronize atomic dipoles inside the cavity and result in superradiance, while a steady-state superradiance can be achieved by re-populating the atomic excited state at a proper rate. [Preview Abstract] |
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K1.00132: A fiber-coupled incoherent light source for ultra-precise optical trapping Tim Menke, Robert Schittko, Anton Mazurenko, M. Eric Tai, Alexander Lukin, Matthew Rispoli, Adam M. Kaufman, Markus Greiner The ability to engineer arbitrary optical potentials using spatial light modulation has opened up exciting possibilities in ultracold quantum gas experiments. Yet, despite the high trap quality currently achievable, interference-induced distortions caused by scattering along the optical path continue to impede more sensitive measurements. We present a design of a high-power, spatially and temporally incoherent light source that bears the potential to reduce the impact of such distortions. The device is based on an array of non-lasing semiconductor emitters mounted on a single chip whose optical output is coupled into a multi-mode fiber. By populating a large number of fiber modes, the low spatial coherence of the input light is further reduced due to the differing optical path lengths amongst the modes and the short coherence length of the light. In addition to theoretical calculations showcasing the feasibility of this approach, we present experimental measurements verifying the low degree of spatial coherence achievable with such a source, including a detailed analysis of the speckle contrast at the fiber end. [Preview Abstract] |
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K1.00133: High-repetition-rate setup for pump-probe time-resolved XUV-IR experiments employing ion and electron momentum imaging Shashank Pathak, Seyyed Javad Robatjazi, Pearson Wright Lee, Kanaka Raju Pandiri, Daniel Rolles, Artem Rudenko J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan KS, USA We report on the development of a versatile experimental setup for XUV-IR pump-probe experiments using a 10 kHz high-harmonic generation (HHG) source and two different charged-particle momentum imaging spectrometers. The HHG source, based on a commercial KM Labs eXtreme Ultraviolet Ultrafast Source, is capable of delivering XUV radiation of less than 30 fs pulse duration in the photon energy range of \textasciitilde 17 eV to 100 eV. It can be coupled either to a conventional velocity map imaging (VMI) setup with an atomic, molecular, or nanoparticle target; or to a novel double--sided VMI spectrometer equipped with two delay-line detectors for coincidence studies. An overview of the setup and results of first pump-probe experiments including studies of two-color double ionization of Xe and time-resolved dynamics of photoionized CO$_{\mathrm{2}}$ molecule will be presented. [Preview Abstract] |
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K1.00134: Filming nuclear dynamics of iodine using x-ray diffraction at the LCLS Matthew Ware, Adi Natan, James Glownia, James Cryan, Phil Bucksbaum We will provide an overview of our analysis of the nuclear dynamics of iodine. At the LCLS, we pumped a gas cell of iodine with a weak 520nm, 50 fs pulse, and the nuclear dynamics are then probed with 9 keV, 40 fs x-rays with variable time delay. This allows us to simultaneously image nuclear wavepackets on the dissociating A state, on the bound B state, and even Raman wavepackets in the ground electronic state. We will explain at length how we isolate each of these signals using a Legendre decomposition of our x-ray data and the selection rules for each of the transitions. Likewise, we will discuss how we convert the x-ray diffraction patterns into real-space movies of the nuclear dynamics. [Preview Abstract] |
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K1.00135: Multiphoton Double Ionization of H$_2$ Y. Li, M. S. Pindzola, J. P. Colgan Multiphoton double ionization probabilities for H$_2$ are calculated using a time-dependent close-coupling method. Total double ionization probabilities are calculated for 2, 3, and 4 photon absorption in the energy range from 10 eV to 50 eV. Single and triple differential probabilities are calculated at photon energies where the total ionization probability is near a maximum. [Preview Abstract] |
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K1.00136: TIME-RESOLVED MOLECULAR DYNAMICS AND FEMTOCHEMISTRY |
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K1.00137: Vibrational relaxation of hot carriers in C$_{\mathrm{60}}$ molecule Mohamed Madjet, Himadri Chakraborty Electron-phonon coupling in molecular systems is at the heart of several important physical phenomena, including the mobility of carriers in organic electronic devices [1]. Following the optical absorption, the vibrational relaxation of excited (hot) electrons and holes to the fullerene band-edges driven by electron-phonon coupling, known as the hot carrier thermalization process, is of particular fundamental interest [2]. Using the non-adiabatic molecular dynamical methodology (PYXAID $+$ Quantum Espresso) based on density functional approach [3], we have performed a simulation of vibrionic relaxations of hot carriers in C$_{\mathrm{60}}$. Time-dependent population decays and transfers in the femtosecond scale from various excited states to the states at the band-edge are calculated to study the details of this relaxation process. [1] Coropceanu et al, Chem. Rev. \textbf{107}, 926 (2007); [2] Ross et al, Nature Materials \textbf{8}, 208 (2009); [3] Madjet et al, Phys. Chem. Chem. Phys. \textbf{18}, 5219 (2016). [Preview Abstract] |
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K1.00138: Modeling Quantum Dynamics in Multidimensional Systems Kyle Liss, Thomas Weinacht, Brett Pearson Coupling between different degrees-of-freedom is an inherent aspect of dynamics in multidimensional quantum systems. As experiments and theory begin to tackle larger molecular structures and environments, models that account for vibrational and/or electronic couplings are essential for interpretation. Relevant processes include intramolecular vibrational relaxation, conical intersections, and system-bath coupling. We describe a set of simulations designed to model coupling processes in multidimensional molecular systems, focusing on models that provide insight and allow visualization of the dynamics. Undergraduates carried out much of the work as part of a senior research project. In addition to the pedagogical value, the simulations allow for comparison between both explicit and implicit treatments of a system's many degrees-of-freedom. [Preview Abstract] |
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K1.00139: Ultrafast photo-dissociation imaged with femtosecond gas electron diffraction Kyle Wilkin, Jie Yang, Ryan Coffee, James Cryan, Markus Guehr, Kareem Hegazy, Renkai Li, Michael Minitti, Pedro Nunes, Xiaozhe Shen, Thomas Wolf, Xijie Wang, Martin Centurion We examine dynamics of single photon excitation in C$_{\mathrm{2}}$F$_{\mathrm{4}}$I$_{\mathrm{2}}$ molecules in the gaseous state using Ultrafast Electron Diffraction (UED). The experiments were performed at SLAC National Laboratory using the MeV gun with sub-200 fs resolution. With UED we can observe dynamics of the molecule with sub-Angstrom resolution. This allows us to view the transient state C$_{\mathrm{2}}$F$_{\mathrm{4}}$I $+$ I before the molecule fully dissociates to C$_{\mathrm{2}}$F$_{\mathrm{4}} \quad +$ 2I. We report on any dynamics observed in the transient state. We also report on differences in the rise time of the dynamics when comparing sub-sections of diffraction patterns both parallel and orthogonal to the polarization of the pump laser. [Preview Abstract] |
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K1.00140: Non-Born-Oppenheimer dynamics in small molecules - connecting experiment and theory Kirk A Larsen, Elio G Champenois, Loren Greenman, C William McCurdy, Thorsten Weber, Daniel S Slaughter A femtosecond pulse of VUV light can coherently excite a wavepacket in a molecule that then evolves on an excited state potential energy surface (PES). This can lead to non-Born-Oppenheimer dynamics via the coupling of electronic and nuclear degrees of freedom near conical intersections of PESs. Even for molecular systems comprised of just a few atoms, its PESs exist in a highly dimensional space. This can make interpreting time-resolved VUV/XUV pump-probe experiments on molecules very challenging, as it can be difficult to ascertain which dimensions of the PESs play central roles in driving the quantum dynamics. Here, I present preliminary results from time-resolved VUV pump-probe electron and ion momentum imaging experiments on simple polyatomic molecules, such as NH$_{\mathrm{3}}$, using a high harmonic generation light source, and discuss the use of parallelized ab initio time-independent molecular electronic structure calculations to give insight into the results of these experiments. In certain cases, even for molecules with highly dimensional PESs, time-independent theory can elucidate observed wavepacket motion. I will also present time-dependent dynamics calculations and discuss the strengths and weaknesses of these approaches to understanding the results our experiments. [Preview Abstract] |
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K1.00141: Ultrafast Polarization Spectroscopy in Polyatomic Molecules Richard Thurston, Niranjan Shivaram, Elio Champenois, Said Bakhti, Pavan Muddukrishna, Ali Belkacem Polarization spectroscopy has been used in the past to study dynamics in solid, liquid and gas phase systems on picosecond and femtosecond time scales. In polarization spectroscopy, two laser pulses (drive and probe) with a relative polarization of 45 degrees, interact with the medium being probed. Due to the third order non-linear polarization induced in the medium a signal with a polarization orthogonal to the probe is generated along the probe direction. This signal measured after a crossed polarizer is directly related to the induced birefringence and dichroism in the medium. Here, we present preliminary measurements in ultraviolet grade fused silica and discuss our model to obtain the ultrafast electronic response of the medium. We then discuss the extension of this method to study ultrafast dynamics in polyatomic molecular systems using multiple pulses. [Preview Abstract] |
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K1.00142: Measuring attosecond time-delays between dissociating vibrational states of D$_2^+$ using a two-color laser field T. Severt, Ben Berry, M. Zohrabi, Peyman Feizollah, Bethany Jochim, Kanaka Raju P., J. McKenna, B. Gaire, K. D. Carnes, G. S. J. Armstrong, D. Ursrey, J. V. Hernandez, F. Anis, B. D. Esry, I. Ben-Itzhak There is considerable interest in studying attosecond time-delays in the photoionization of neighboring electronic states of atomic and more complex targets. The underlying assumption of that work is that electron dynamics are responsible for such short delays, since they match the natural electronic timescale. Recent theoretical work has shown that the two-color dissociation probability of adjacent vibrational states in the HeH$^+$ molecule exhibit time-delays of tens of attoseconds. Since electronic excitation is negligible in HeH$^+$ for the considered laser parameters, this demonstrates that attosecond delays occur for purely nuclear motion. Here, we present an analogous experiment on a D$_2^+$ ion beam, where attosecond time-delays are observed using an intense two-color (800/400-nm) laser field. In the two-color field, interfering pathways ending in opposite parity states result in a spatial asymmetry with respect to the laser polarization. By comparing the phase shifts of the spatial asymmetry parameter between the $v=7$ and $v=8$ vibrational states of the $1s\sigma_g$, we observe a $53$-as delay. [Preview Abstract] |
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K1.00143: Time-resolved electron and ion imaging to investigate ultrafast structural dynamics in gas-phase halomethane molecules F. Ziaee, A. Rudenko, D. Rolles, E. Savelyev, C. Bomme, R. Boll, B. Manschwetus, B. Erk, S. Trippel, J. Wiese, J. Kupper, K. Amini, J. Lee, M. Brouard, F. Brausse, A. Rouzee, P. Olshin, A. Mereshchenko, J. Lahl, P. Johnsson, M. Simon, T. Marchenko We investigate structural dynamics in halomethane molecules (CH$_{\mathrm{3}}$I, CH$_{\mathrm{2}}$IBr, and CH$_{\mathrm{2}}$ICl) within a UV pump-IR probe scheme, in which the UV pulse initiates a photodissociation reaction, and the delayed IR-probe pulse ionizes the molecule. The produced electrons and ions are imaged by a double-sided velocity map imaging (VMI) spectrometer. Delay-dependent yields and momentum distributions of ionic fragments are recorded with the PImMS camera [1]. Simultaneously, angle-resolved electron spectra are recorded on the other side of the spectrometer. We observe large changes in the yield and kinetic energy of various fragment ions along with subtler changes in the electron spectrum, from which we extract dissociation dynamics of the molecule information. [1] K. Amini et al., Rev. Sci. Instrum. \textbf{86}, 103113 (2015) [Preview Abstract] |
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K1.00144: Femtosecond Time-Resolved Photoelectron Imaging of Excited Doped Helium Nanodroplets Catherine Saladrigas, Camila Bacellar, Stephen R. Leone, Daniel M. Neumark, Oliver Gessner Helium nanodroplets are excellent matrices for high resolution spectroscopy and the study of ultracold chemistry. They are optically transparent. In their electronic ground state, interact very weakly with any atomic or molecular dopant. Electronically excited droplets, however, can strongly interact with dopants through a variety of relaxation mechanisms. Previously, these host-dopant interactions were studied in the energy domain, revealing Penning ionization processes enabled by energy transfer between the droplet host and atomic dopants. Using femtosecond time resolved XUV photoelectron imaging, we plan to perform complementary experiments in the time domain to gain deeper insight into the timescales of energy transfer processes and how they compete with internal droplet relaxation. First experiments will be performed using noble gas dopants, such as Kr and Ne, which will be compared to previous energy-domain studies. Femtosecond XUV pulses produced by high harmonic generation will be used to excite the droplets, IR and near-UV light will be used to monitor the relaxation dynamics. Using velocity map imaging, both photoelectron kinetic energies and angular distributions will be recorded as a function of time. Preliminary results and proposed experiments will be presented. [Preview Abstract] |
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K1.00145: ION-ATOM, ION-ION COLLISIONS |
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K1.00146: Thin film deposition using rarefied gas jet Dr. Sahadev Pradhan The rarefied gas jet of aluminium is studied at Mach number \textit{Ma }$=$\textit{ (U\textunderscore j / }$\backslash $\textit{sqrt\textbraceleft kb T\textunderscore j / m\textbraceright )}in the range \textit{.01 \textless Ma \textless 2}, and Knudsen number \textit{Kn }$=$\textit{ (1 / (}$\backslash $\textit{sqrt\textbraceleft 2\textbraceright }$\backslash $\textit{pi d\textasciicircum 2 n\textunderscore d H)} in the range \textit{.01 \textless Kn \textless 15}, using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations, to understand the flow phenomena and deposition mechanisms in a physical vapor deposition (PVD) process for the development of the highly oriented pure metallic aluminum thin film with uniform thickness and strong adhesion on the surface of the substrate in the form of ionic plasma, so that the substrate can be protected from corrosion and oxidation and thereby enhance the lifetime and safety, and to introduce the desired surface properties for a given application. Here, $H$is the characteristic dimension, \textit{U\textunderscore j}and \textit{T\textunderscore j}are the jet velocity and temperature, \textit{n\textunderscore d}is the number density of the jet, $m$and $d$ are the molecular mass and diameter, and \textit{kb}is the Boltzmann constant. An important finding is that the capture width (cross-section of the gas jet deposited on the substrate) is symmetric around the centerline of the substrate, and decreases with increased Mach number due to an increase in the momentum of the gas molecules. DSMC simulation results reveals that at low Knudsen number \textit{((Kn }$=$\textit{ 0.01);}shorter mean free paths), the atoms experience more collisions, which direct them toward the substrate. However, the atoms also move with lower momentum at low Mach number$,$which allows scattering collisions to rapidly direct the atoms to the substrate. [Preview Abstract] |
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K1.00147: Positronium formation from C$_{\mathrm{60}}$ Paul-Antoine Hervieux, Anzumaan Chakraborty, Himadri Chakraborty Due to the dominant electron capture by positrons from the molecular shell and the spatial dephasing across the shell-width, a powerful diffraction effect universally underlies the positronium (Ps) formation from C$_{\mathrm{60}}$. This results into trains of resonances in the Ps formation cross section as a function of the positron beam energy [1], producing structures in recoil momenta in analogy with classical single-slit diffraction fringes in the configuration space. C$_{\mathrm{60}}$ is modeled by a jellium-based local-density approximation (LDA) method [2] and the Ps formation is treated by the continuum distorted-wave final-state (CDW-FS) approximation [3]. The work may motivate application of the Ps formation spectroscopy to gas-phase nanoparticles and also the access target-level- as well as Ps-level-differential measurements. [1] Hervieux et al (submitted), \underline {arXiv:1610.00335 [physics.atm-clus]}; [2] Choi et al (submitted), \underline {arXiv:1610.00346}\underline {\textbf{~}}\underline {[physics.atm-clus]}; [3] Fojon et al, Phys. Rev. A \textbf{54}, 4923 (1996) [Preview Abstract] |
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K1.00148: Vortices for Ps formation in positron-hydrogen collisions S. J. Ward, P. Van Reeth, Albandari W. Alrowaily We have found two deep minima in the differential cross section for Ps formation in positron-hydrogen collisions in the Ore Gap. Each minimum has been shown to correspond to a vortex in the velocity field associated with the scattering amplitude. The velocity field rotates about the position where the real and imaginary parts of the scattering amplitude are zero. For the first zero, we have verified that the magnitude of the circulation [1] is $2\pi/M$, where $M$ is the mass of the outgoing Ps. [1.] Iwo Bialynicki-Birula, Zofia Bialynicka-Birula, and Cezary \'Sliwa, Phys.~Rev.~A {\bf 61}, 032110 (2000). [Preview Abstract] |
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K1.00149: Spectral Resolution of Resonant Positron-Molecule Annihilation due to Multimodes. J. R. Danielson, M. R. Natisin, C. M. Surko The annihilation spectra of positrons on molecules, as a function of incident positron energy, are typically dominated by relatively sharp features that have been identified as vibrational Feshbach resonances (VFR) mediated by fundamental vibrations.\footnote{\small G. F. Gribakin, J. A. Young, C. M. Surko, {\it Rev. Mod. Phys.} {\bf 82}, 2557 (2010).} The theory of Gribakin and Lee is successful in describing the annihilation spectra for selected small molecules where the annihilation is dominated by a small number of dipole-allowed modes.\footnote{\small G. F. Gribakin, C. M. R. Lee, {\it Phys. Rev. Lett.} {\bf 97}, 193201 (2006).} However, in most molecules, these sharp peaks ride on a broad background of enhanced annihilation. There is indirect evidence that this effect is due to a dense set of combination and overtone resonances.\footnote{\small A. C. L. Jones, {\it et al.}, {\it Phys. Rev. Lett.} {\bf 108}, 093201 (2012).} An extension of the Gribakin-Lee theory can be used to describe VFR's due to these multimodes, where the important effect of multiple decay channels is also included. Prospects for resolving these features using a new high-resolution positron beam will be discussed. [Preview Abstract] |
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K1.00150: Computation of Electron Impact Ionization Cross sections of Iron Hydrogen Clusters -- Relevance in Fusion Plasmas Umang Patel, K N Joshipura Plasma-wall interaction (PWI) is one of the key issues in nuclear fusion research. In nuclear fusion devices, such as the JET tokamak or the ITER, first-wall materials will be directly exposed to plasma components. Erosion of first-wall materials is a consequence of the impact of hydrogen and its isotopes as main constituents of the hot plasma. Besides the formation of gas-phase atomic species in various charge states, di- and polyatomic molecular species are expected to be formed via PWI processes. These compounds may profoundly disturb the fusion plasma, may lead to unfavorable re-deposition of materials and composites in other areas of the vessel. Interaction between atoms, molecules as well transport of impurities are of interest for modelling of fusion plasma. $Q_{ion}$ by electron impact are such process also important in low temperature plasma processing, astrophysics etc. We reported electron impact $Q_{ion\thinspace }$for iron hydrogen clusters, FeH$_{\mathrm{n}}$ (n $=$ 1 to 10) from ionization threshold to 2000eV. A semi empirical approach called Complex Scattering Potential -- Ionization Contribution (CSP-\textit{ic}) has been employed for the reported calculation$^{\mathrm{1}}$. In context of fusion relevant species $Q_{ion}$ were reported for beryllium and its hydrides, tungsten and its oxides and cluster of beryllium-tungsten by Huber \textit{et al}$^{\mathrm{2}}$. Iron hydrogen clusters are another such species whose $Q_{ion}$ were calculated$^{\mathrm{2}}$ through DM and BEB formalisms, same has been compared with present calculations. $^{\mathrm{1}}$U. R. Patel \textit{et al}, J. Chem. Phys, \textbf{140} (2014) 44302 $^{\mathrm{2}}$S. E. Huber \textit{et al}, Eur. Phys. J. D. 70 (2016) 182 [Preview Abstract] |
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K1.00151: Quantum Chemistry and Non-equilibrium Thermodynamics in an Atom-Ion Hybrid Trap Michael Mills, Prateek Puri, Steven Schowalter, Alex Dunning, Christian Schneider, Eric Hudson In this presentation we describe work conducted with the MOTion trap - a hybrid atom-ion trap consisting of a linear quadrupole ion trap (LQT) and a co-located magneto-optical trap (MOT). With the long interrogation times associated with the ion trap and precisely tunable entrance channels of both the atom and ion via laser excitation, the MOTion trap is a convenient platform for the study of quantum state resolvable cold chemistry. We describe a recent study of excited state chemistry between cold Ca atoms and the BaOCH3$+$ molecular ion, which has resulted in the product BaOCa$+$, the first observed mixed hypermetallic alkaline earth oxide molecule. Further, due to the complexity of ion-ion heating within an LQT and micromotion interruption collisions, there remain many open questions about the thermodynamics of ions in a hybrid trap environment. We describe an analytical model that explains the thermodynamics of these systems as well an experimental effort confirming one of the more interesting hallmarks of this model, the bifurcation in steady state energy of ions immersed in an ultracold gas. [Preview Abstract] |
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K1.00152: Effect of viscosity on propagation of MHD waves in astrophysical plasma. Alemayehu Cherkos We determine the general dispersion relation for the propagation of magnetohydrodynamic (MHD) waves in an astrophysical plasma by considering the effect of viscosity with an anisotropic pressure tensor. Basic MHD equations have been derived and linearized by the method of perturbation to develop the general form of the dispersion relation equation. Our result indicates that an astrophysical plasma with an anisotropic pressure tensor is stable in the presence of viscosity and a strong magnetic field at considerable wavelength. [Preview Abstract] |
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K1.00153: Electron transfer, ionization, and excitation in collisions between protons and the ions F$^{8+}$ and Ne$^{9+}$ Thomas Winter Coupled-state cross sections are being determined for electron transfer, ionization, and excitation in collisions between keV-energy protons and the hydrogenic ions F$^{8+}$ and Ne$^{9+}$ initially in the ground state, extending early\footnote{T. G. Winter, Phys. Rev. A {\bf 35}, 3799 (1987).} and more recent work\footnote{T. G. Winter, Phys. Rev. A {\bf 87}, 032704 (2013).} on the less highly charged target ions He$^{+}$, Li$^{2+}$, Be$^{3+}$, B$^{4+}$, and C$^{5+}$, and work reported at the 2016 DAMOP meeting on the target ions N$^{6+}$ and O$^{7+}$. As in the more recent works, a basis of 60 Sturmians on each center is being used, and in a second calculation, a basis of 280 Sturmians on the target nucleus and a single $1s$ function on the proton is being used. The extent to which high-energy scaling rules with target nuclear charge $Z$ are valid is being examined further for transfer to the ground state, total transfer, and ionization, as well as for excitation and individual-state processes at intermediate energies near where the cross sections peak, and at lower energies. [Preview Abstract] |
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K1.00154: Towards Laser Controlled Generation of Rydberg State, One-Electron Ions Joan Dreiling, Aung Naing, Joseph Tan We report on progress towards the goal of producing hydrogen-like ions in Rydberg states for laser spectroscopy measurements of fundamental constants [1]. Fully stripped neon atoms (Ne$^{\mathrm{10+}})$ are produced in an electron beam ion trap (EBIT). These bare nuclei are extracted via a beamline from the EBIT into a second apparatus where they are captured at low energy in a unitary Penning trap [2]. The second apparatus has a cross-beam configuration, with a perpendicular beam of laser excited Rb atoms intersecting the ion beam at the Penning trap. While stored in the trap, the ions can interact with the Rb and, through charge exchange interactions, the bare nuclei can capture one or more electrons from the Rb. The charge states of the stored ions can then be analyzed by dumping the ions from the trap to a time-of-flight (TOF) detector [2]. To search for enhanced electron capture due to the laser excitation, initial studies compare the charge exchange rates in the TOF data for ground state Rb and for laser excited Rb. [1] U.D. Jentschura et al., Phys. Rev. Lett. \textbf{100}, 160404 (2008). [2] S.F. Hoogerheide et al., Atoms \textbf{3}, 367 (2015). [Preview Abstract] |
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K1.00155: Radiative collisional processes for atoms and ions J.F. Babb, B. M. McLaughlin We describe theoretical studies of radiative collisional processes between atoms and ions. The cross sections and rate coefficients for the radiative charge transfer process between a carbon atom and a helium ion (C-He${}^+$) [1] and between other atom-ion pairs are calculated. The radiative association process is investigated for a carbon atom and a proton (C-H${}^+$) and for other atom-ion systems. Applications of the results are discussed. [1] J.F. Babb and B. M. McLaughlin, J. Phys. B 50 (2017), 044003. [Preview Abstract] |
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K1.00156: Quantum-State-Resolved Ion-Molecule Chemistry Tiangang Yang, Gary Chen, Eric Hudson, Wesley Campbell We are working towards a new platform for quantum-state-resolved ion-molecule chemistry by utilizing a combination of cryogenic buffer gas cooling, laser-cooled ion sympathetic cooling, and integrated mass spectrometry in an RF Paul trap. Cold molecular species produced in a cryogenic buffer gas beam collide with target atomic carbon ions in an linear quadrupole trap. Ion imaging and time of flight mass spectrometry are then used to observe the resulting reaction rates and products. We can utilize the precision control over quantum states allowed by this neutral-plus-ion chemistry environment (N$+$ICE) to resolve state-resolved quantum chemical reactions without high-density molecular sample production; proposed extensions suggest true state-to-state chemistry is possible in this system. We report progress towards cold carbon and water chemistry, including co-trapping and sympathetic cooling of carbon ions with laser-cooled beryllium ions. [Preview Abstract] |
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K1.00157: Fully differential study on projectile coherence effects in ionization of helium by protons Sachin Sharma, T Arthanayaka, B.R Lamichhane, A Hasan, S Borbély, F Járai-Szabó, L Nagy, Michael Schulz Atomic-fragmentation experiments have played a crucial role in our understanding of the dynamic few-body processes. Despite incredible progress in the field, puzzling discrepancies between theory and experimental still exist for some very fundamental collision systems e.g. single ionization of He by 100 MeV/a.m.u C6$+$ ions. In recent years, a possible explanation for these discrepancies has been explored through various experimental studies on ``Projectile Coherence Effects'' (PCE). Here, we present a fully differential study on single ionization of helium by 75 keV protons. FDCS were measured for two different transverse projectile coherence lengths i.e. 1 a.u. and 3.5 a.u.. Substantial differences between the FDCS were observed, once again signifying pronounced PCE. The FDCS for the large PCL contain an interference term due to a coherent superposition of different impact parameters that are leading to the same scattering angles, which is suppressed for the small PCL. The experimental data have been qualitatively well reproduced by a non-perturbative ab initio time-dependent model, which treats the projectile coherence properties in terms of a wave-packet. [Preview Abstract] |
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K1.00158: ELECTRON-ATOM COLLISIONS |
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K1.00159: Analytic descriptions of ultracold electron-atom collisions Bo Gao, Alex Dalgarno From the quantum defect theory\footnote{Gao, PRL, \textbf{104}, 213201 (2010); PRA, \textbf{88}, 022701 (2013).} (QDT) and the multichannel quantum defect theory\footnote{Li \textit{et al.}, PRA \textbf{89}, 052704 (2014); Li and Gao, PRA \textbf{91}, 032702 (2015).} (MQDT) for an attractive polarization potential, we derive both a QDT expansion and a MQDT expansion, that together provide analytic descriptions of low-energy electron collisions with atoms in a ground $^1S$ or a ground $^2S$ state. The expansions are accurate over an energy range from the zero kelvin to hundreds of kelvins, and include effects of hyperfine structure if it is present in cases of $^2S$ atoms. Results for electron-hydrogen hyperfine-changing collisions are presented as an example. [Preview Abstract] |
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K1.00160: Free-free experiments in potassium: the search for dressed-atom effects C.M. Weaver, B.N. Kim, N.L.S. Martin, B.A. deHarak The absorption or emission of radiation during the collision of charged particles with atoms and molecules is investigated in the so-called free-free experiments. Up to now almost all such experiments have been in agreement with a simple theory which assumes that the interaction of the radiation with the atom itself has no effect on the scattering process. Very recently the first experiments to observe the unambiguous breakdown of this assumption have been carried out in xenon by Morimoto, Kanya, and Yamanouchi.\footnote{Y. Morimoto, R. Kanya, and K. Yamanouchi, Phys.\ Rev.\ Lett.\ {\bf 115}, 123201 (2015)} An estimate of the dressing of the target by the radiation's electric field may be made in terms of the electric dipole polarizability of the target. The effects in Xe were extremely difficult to measure because they occur at very small scattering angles. We have begun to carry out experiments in potassium which has a polarizability an order of magnitude larger than Xe. Estimates show that the dressing effects in potassium should be observed at scattering angles easily accessible to experiments, and without the need for complicated corrections. [Preview Abstract] |
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K1.00161: Comprehensive out-of-plane ($e,2e$) measurements on He autoionizing levels N.L.S. Martin, B.N. Kim, C.M. Weaver, B.A. deHarak, O. Zatsarinny, K. Bartschat We report out-of-scattering-plane $(e,2e)$ measurements on helium $2\ell2\ell'$ auto\-ionizing levels for 80, 100, 120, 150, and 488 eV incident electron energies, and scattering angles 60$^\circ$, 50.8$^\circ$, 45$^\circ$, 39.2$^\circ$, and 20.5$^\circ$, respectively. The kinematics are similar in all cases: ejected electrons are detected in a plane that contains the momentum transfer direction and is perpendicular to the scattering plane, and the momentum transfer is 2.1~a.u..\footnote{B.A. deHarak, K. Bartschat, and N.L.S. Martin, Phys. Rev. Lett. {\bf 100}, 063201 (2008)} The results are presented as $(e,2e)$ angular distributions energy-integrated over each level, and are compared with our second-order theory calculated for 488 eV incident electron energy, as well as predictions based on a fully non-perturbative close-coupling model. At all energies except 80 eV, the shapes of the angular distributions, and the recoil peak intensities, are in excellent agreement with the 488 eV results for all three autoionizing levels. The reasons why this is so, for incident energies that vary by almost a factor of five, is at present unclear. [Preview Abstract] |
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K1.00162: Spin entanglement in elastic electron scattering from quasi-one electron atoms. Samantha Fonseca dos Santos, Klaus Bartschat We have extended our work on e-Li collisions [1] to investigate low-energy elastic electron collisions with atomic hydrogen and other alkali targets (Na,K,Rb). These systems have been suggested for the possibility of continuously varying the degree of entanglement between the elastically scattered projectile and the valence electron [2,3]. In order to estimate how well such a scheme may work in practice, we carried out overview calculations for energies between 0 and 10 eV and the full range of scattering angles~$0^\circ - 180^\circ$. In addition to the relative exchange asymmetry parameter that characterizes the entanglement, we present the differential cross section in order to estimate whether the count rates in the most interesting energy-angle regimes are sufficient to make such experiments feasible in practice. [1] K.~Bartschat and S.~Fonseca dos Santos, arXiv:1611.06180. [2] K.~Blum and B.~Lohmann, Phys.\ Rev.\ Lett.~{\bf 116} (2016) 033201. [3] B.~Lohmann, K.~Blum, and B.~Langer, Phys.\ Rev.\ A~{\bf 94} (2016) 032331. [Preview Abstract] |
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K1.00163: Benchmark calculations for electron-impact excitation of Mg$^{4+}$. Kedong Wang, Luis Fern\'{a}ndez-Menchero, Oleg Zatsarinny, Klaus Bartschat There are major discrepancies between recent B-spline R-matrix (BSR) [1] and Dirac Atomic R-matrix Code (DARC) [2] calculations regarding electron-impact excitation rates for transitions in $\mathrm{Mg}^{4+}$. To identify possible reasons for these discrepancies and to estimate the accuracy of the various results, we carried out independent BSR calculations with the same 86 target states as in the previous calculations, but with a more accurate representation of the target structure. We find close agreement with the results given in~[2] for the majority of transitions. The remaining discrepancies in the collision strengths are mostly due to the different structure description, specifically the inclusion of correlation effects, and the likely occurrence of pseudo\-resonances in the DARC calculations. To further check the convergence of the predictions, we carried out even more extensive calculations by coupling 316 states of $\mathrm{Mg}^{4+}$. Extending the close-coupling expansion results in major corrections for transitions involving the high-lying states and allows us to assess the likely uncertainties in the existing datasets. [1] K.~M.~Aggarwal and F.~P.~Keenan, Can.\ J.~Phys.~{\bf 95} (2017)~9. [2] S.~S.~Tayal and A.~M.~Sossah, Astron.\ Astroph.~{\bf 574} (2015) A87. [Preview Abstract] |
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K1.00164: Novel mechanism for creating long-lived metastable atomic negative ions Alfred Msezane, Zineb Felfli A novel mechanism is proposed for creating long-lived metastable atomic negative ions in complex atoms, such as the lanthanides. It exploits the orbital collapse of the 5d orbital in Gd (Z$=$64) into the 4f orbital of Tb (Z$=$65). In the region of collapse the properties of the 5d and 4f orbitals are quite sensitive to the changes in the effective potential. Consequently the collapse phenomenon impacts the core-polarization interaction significantly in the relevant atom, namely Tb inducing a new excited Tb\textasciimacron anion. The mechanism is demonstrated in the lanthanide atoms Tb and Dy through the appearance of long-lived Tb\textasciimacron and Dy\textasciimacron anions in the Regge pole calculated electron elastic total cross sections. Ground and long-lived metastable negative ion formation occurs at the second Ramsauer -Townsend minima. [Preview Abstract] |
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K1.00165: Monitoring GaAs photocathode heat cleaning temperature Nathan Clayburn, Kenneth Trantham, Matthew Dunn, Timothy Gay Before a GaAs photocathode can be ``activated'' to achieve a negative electron affinity condition, the GaAs crystal must be cleaned. This is most commonly done by ohmic, radiative, or electron bombardment heating. We report a new technique to monitor the temperature of heated GaAs photocathodes by observation with a camera. The method is robust and yields the same temperatures for different GaAs samples heated using different methods in different mounting configurations. [Preview Abstract] |
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K1.00166: Elastic scattering of electrons and positrons by Pb atoms Bidhan Saha, A. K. Basak, M. A. Uddin, A. K. F. Haque, M. I. Hossain, M. M. Haque, M. A. R. Patoary, M. Maaza The elastic scattering of e$^{\mathrm{\pm }}$ - Pb atoms is reported for 10 eV $\le $E $\le $ 1 keV\textbf{. }A complex optical potential embodying the static, exchange, polarization and absorption potentials is used to solve Dirac equations [1] by partial wave analysis. For electron case the absorption strength (W$_{\mathrm{abs}})$ plays an important role; it increases monotonically from E\textgreater 30 eV but its low energy peak may be due to dispersion effect at the inelastic threshold. As compared to other theoretical values [2] our results show good agreement with available experimental cross sections [3]. [1] P.A.M. Dirac, \textit{Principles of Quantum Mechanics}. International Series of Monographs on Physics (4th ed.), Oxford University Press. p.~255. (1958).. [2] P. Kumar, A. K. Jain, A. N. Tripathi, and S. N. Nahar, Phys. Rev. A 49, 899 (1994). [3] S. Tosic, M. S. Rabasovic, D. Sevic, V. Pejcev, D. M. Filipovic, L. Sharma, A. N. Tripathi, R. Srivastava, and B. P. Marinkovic, Phys. Rev. A77, 012725 (2008). [Preview Abstract] |
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K1.00167: Dielectronic Recombination of Si-Like Ions and the Low-temperature S$^{2+}$ Orion Nebula Abundance Conundrum Jagjit Kaur, Thomas Gorczyca, Nigel Badnell We describe detailed calculations for the dielectronic recombination (DR) of the Si-like isoelectronic sequence. Our theoretical methodology begins with the perturbative, multi-configurational Breit-Pauli code AUTOSTRUCTURE for efficient yet comprehensive calculations along the entire sequence. We have also investigated, using more sophisticated R-matrix and multi-configuration Hartree-Fock (MCHF) approaches, the low-energy DR resonances. The resultant DR rate coefficients at lower temperatures are extremely sensitive to the theoretically-predicted near-threshold resonance energy positions. This problem is especially acute for near-neutral Si-like ions, including the uncertainties in the S$^{2+}$ DR rate coefficient, an important parameter in astrophysical plasma models for the sulfur ionization balance in the Orion nebula. The computed DR rate coefficients comprise part of the assembly of the DR data base required in the modeling of dynamic finite density plasmas. [Preview Abstract] |
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K1.00168: Doubly excited states of atomic negative ions Matthew Eiles, Chris Greene Doubly excited states of negative ions reveal the intricate details of electron correlations and depend sensitively on the structure of the excited atomic state. In hydrogen, the degenerate states of the excited atom form a permanent dipole, leading to the dipole series of doubly excited resonances \footnote{M. Gailitis and R. Damburg, Proc. Phys. Soc. 82, 192 (1963)}. In other species, the non-degenerate excited states instead form induced dipole potentials, but for higher partial waves their increasingly small energy splittings can lead to both polarization terms in the asymptotic potentials. We theoretically investigate the high partial wave cross sections measured recently \footnote{Lindahl et al. PRL 108, 033004 (2012)} using the eigenchannel R-Matrix method to understand the role of these potentials in the observed photodetachment cross sections. We also explore the interactions between a doubly excited hydrogen negative ion and a neutral atom, using analogies to Rydberg molecules. Just as a Rydberg electron can bind to an atom within its large ($R\sim n^2$) orbit, the outer electron of a doubly excited H- ion can also bind to an atom in its exponential orbit, $R\sim\exp(n)$. We use the Fermi pseudopotential to investigate the possibility of forming exotic molecules. [Preview Abstract] |
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K1.00169: SPECTROSCOPY, LIFETIMES, OSCILLATOR STRENGTHS |
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K1.00170: Laser Spectroscopy of $^{176}\mathrm{Lu}^{+}$ Rattakorn Kaewuam, Arpan Roy, Kyle Arnold, Murray Barrett Singly ionized lutetium $^{176}\mathrm{Lu}^+$ possesses low-lying metastable D levels where the corresponding decay channels have been proposed as promising optical clock transitions. Here we report laser spectroscopy of the $^3D_1$, $^3D_2$, $^3P_0$, and $^3P_1$ levels relative to the $^1S_0$ ground state. The hyperfine structure for each level, the allowed E1 transitions for detection and cooling, and clock transitions are all determined. These measurements provide a useful reference for establishing optical clock operation with this ion. [Preview Abstract] |
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K1.00171: Relativistic many-body calculation of energies, multipole transition rates, and lifetimes in molybdenum ions Dadong Huang, Z. Zuhrianda, M. S. Safronova, U. I. Safronova Accurate calculations of atomic properties for systems with $3d^n$ valence configurations are complicated by strong correlation corrections. In this work, we apply the relativistic hybrid approach that combines the configuration interaction and the coupled cluster methods to this problem. We chose molybdenum ions with two, three, and four valence electrons as testing cases. The $4d^4$, $4d^35s$, $4d^35d$, $4d^36s$ even-parity states and the $4d^35p$ and $4d^25s5p$ odd-parity states are considered for Zr-like Mo$^{2+}$. The $4d^3$ and $4d^25p$ states are considered for Y-like Mo$^{3+}$, and $4d^2$, $4d5s$, $4d5d$, and $4d5p$ states are considered for Sr-like Mo$^{4+}$. Energy levels, multipole (E1, M1, and E2) matrix elements, and lifetimes are evaluated for all three ions. The energy results are compared with the experimental values for benchmark tests of the method performance for these configuration [Preview Abstract] |
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K1.00172: Photoelectron Angular Distributions of Rotationally Resolved Autoionizing States of Molecular Nitrogen Alexander M. Chartrand, Ugo Jacovella, David M. P. Holland, Berenger Gans, Stephen T. Pratt, Laurent Nahon, Gustavo A. Garcia, Xiaofeng Tang, Elizabeth F. McCormack Rotationally resolved excitation of N$_2$ just above the ionization threshold allowed the recording of photoelectron angular distributions (PADs) for selected autoionizing levels of the ($X^+\,^2\Sigma^+_g$) $6p\sigma$, $v=2$ and ($X^+\,^2\Sigma^+_g$) $9f$, $v=1$ Rydberg states. Because the direct ionization continuum is weak compared to the autoionizing resonances, the PADs can be predicted using simplified formulae based on the work of Raoult \emph{et al.} [\emph{J. Chim. Phys.} {\bf 77}, 599 (1980)]. The observed PADs are generally in good agreement with these predictions. Photoelectron angular distributions were also recorded for individual rotational levels of the $b' {\,}^1\Sigma_u^+$, $v = 42$ and 43 states, and for two complex resonances arising from the interactions between the $b'$ state and Rydberg states converging to the $X^+$, $A^+$, and $B^+$ states of the ion. The analysis of these PADs is more complex and is still underway. [Preview Abstract] |
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K1.00173: Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Ge II Negar Heidarian, Richard E. Irving, Steven R. Federman, David G. Ellis, Song Cheng, Larry J. Curtis Better understanding of the atomic structure for atomic ions requires experimental measurements for lifetimes and oscillator strengths which also serve as a test for theoretical calculations. Furthermore, interpreting astronomical observations of atomic ions requires knowledge of their oscillator strengths and transition probabilities. We present the results of lifetime measurements with beam-foil techniques performed with the Toledo Heavy-Ion Accelerator on levels of interest in Ge~{\footnotesize II} producing transitions to the ground term at 1237.1 {\AA} and 1261.9 {\AA} ($4s^{2}4d$ $^{2}D_{3/2}$ and $4s^{2}4d$ $^{2}D_{5/2}$, respectively). Oscillator strengths are derived from the lifetimes, and our experimental results are compared with our MCDHF\footnote[2] {P. J{\"{o}}nsson et al., The Computational Atomic Structure Group (2014)} calculations using the development version of the GRASP2K package\footnote[3] {P. J{\"{o}}nsson et al., Comput. Phys. Commun. 184, 2197 (2013)} as well as the latest calculations done by others. We also provide an overall comparison of our studies on the $ns^{2}nd$ $^{2}D$ and $nsnp^{2}$ $^{2}D$ terms in three elements of group~{\footnotesize IV} of the periodic table, namely Pb~{\footnotesize II}, Sn~{\footnotesize II} and Ge~{\footnotesize II}. [Preview Abstract] |
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K1.00174: Relativistic many-body calculation of energies, multipole transition rates, and lifetimes of tungsten ions U. I. Safronova, M. S. Safronova, N. Nakamura Atomic properties of Cd-like W$^{26+}$, In-like W$^{25+}$, and Sn-like W$^{24+}$ ions are evaluated using a relativistic CI+all-order approach that combines configuration interaction and the coupled-cluster methods. The energies, transition rates, and lifetimes of low-lying levels are calculated and compared with available theoretical and experimental values. The magnetic-dipole transition rates are calculated to determine the branching ratios and lifetimes for the $4f^3$ states in W$^{25+}$ and for the $4f^4$ in W$^{24+}$ ions. We also evaluated the atomic properties of these ions using the Hebrew University Lawrence Livermore Atomic (HULLAC) code and demonstrated higher accuracy of the wavelength values obtained using the CI+all-order approach. [Preview Abstract] |
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K1.00175: Hyperfine Structure of the B State and Predictions of Optical Cycling Behavior of the X-B transition in TlF Eric Norrgard, Eustace Edwards, Daniel McCarron, Matthew Steinecker, David DeMille, Shah Alam, Stephen Peck, Neha Wadia, Larry Hunter The rotational and hyperfine spectrum of the $X^1\Sigma^+ \rightarrow B^3\Pi_1$ transition in TlF molecules was measured using laser excitation and detection of the resulting fluorescence from a molecular beam. Rotational and hyperfine constants are obtained from a least-squares analysis. The large magnetic hyperfine interaction of the Tl nuclear spin leads to significant mixing of the lowest $B$ state rotational levels. Updated, more precise measurements of the $B\rightarrow X$ vibrational branching fractions are also presented. The combined rovibrational branching fractions allow for the prediction of the number of photons that can be scattered in a given TlF optical cycling scheme, which will be critical knowledge for the CeNTREX collaboration's upcoming precision measurement of the Schiff Moment of the Tl nucleus using TlF. [Preview Abstract] |
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K1.00176: Analysis of monochromatic and quasi-monochromatic X-ray sources in imaging and therapy Maximillian Westphal, Sara Lim, Sultana Nahar, Christopher Orban, Anil Pradhan We studied biomedical imaging and therapeutic applications of recently developed quasi-monochromatic and monochromatic X-ray sources [1]. Using the Monte Carlo code GEANT4, we found that the quasi-monochromatic 65 keV Gaussian X-ray spectrum created by inverse Compton scattering with relatavistic electron beams were capable of producing better image contrast with less radiation compared to conventional 120 kV broadband CT scans [3]. We also explored possible experimental detection of theoretically predicted K$\alpha$ resonance fluorescence in high-Z elements [2] using the European Synchrotron Research Facility with a tungsten (Z = 74) target. In addition, we studied a newly developed quasi-monochromatic source generated by converting broadband X-rays to monochromatic K$\alpha$ and $\beta$ X-rays with a zirconium target (Z = 40). We will further study how these K$\alpha$ and K$\beta$ dominated spectra can be implemented in conjunction with nanoparticles for targeted therapy.\newline 1. S.N.Lim, et al, JRR 56, 77 (2015)\newline 2. S.N.Nahar, A.K. Pradhan, JQSRT 155, 32 (2015)\newline 3. S.N.Lim\&M.S.Westphal, et al, PMB (submitted 2017)\newline Acknowledgement: Ohio Supercomputer Center, Columbus, OH [Preview Abstract] |
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K1.00177: Experimental Potential Energy Curve for the 4$^3\Pi$ Electronic State of NaCs Andrew Steely, Hannah Cooper, Hareem Zain, Ciara Whipp, Carl Faust, Andrew Kortyna, John Huennekens We present results from experimental studies of the 4$^3\Pi$ electronic state of the NaCs molecule. This electronic state is interesting in that its potential energy curve likely exhibits a double minimum. As a result, interference effects are observed in the resolved bound-free fluorescence spectra. The optical-optical double resonance method was used to obtain Doppler-free excitation spectra for the 4$^3\Pi$ state. This dataset of measured level energies was expanded largely by observing fluorescence from levels populated by collisions. To aid in level assignments, simulations of resolved bound-free fluorescence spectra were calculated using the BCONT program (R. J. Le Roy, University of Waterloo). Spectroscopic constants were determined to summarize data belonging to inner well, outer well, and above barrier regions of the electronic state. Current work focuses on using the IPA method to construct an experimental potential energy curve. [Preview Abstract] |
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K1.00178: Study of electron correlations in Helium double Rydberg wave packets Xiao Wang, Francis Robicheaux The correlation between two bound electrons as a three-body Coulomb problem remains an interesting topic. We have performed fully quantum and classical calculations on a Helium atom with two excited Rydberg wave packets. Changing the central energies and the energy widths of the wave packets may lead to totally different behavior of the system, such as faster autoionization rates or more stable trajectories. We also studied field-caused double ionizations of this system with THz short pulses, where the results can be used to study the wavefunction structure of the system during autoionization process. [Preview Abstract] |
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K1.00179: Towards Er-K quantum gas mixtures Jackson Angonga, Bryce Gadway We present our efforts towards developing a system that will trap and cool atomic mixtures of erbium and potassium. We highlight the first polarization spectroscopy measurements of erbium, which will be used to stabilize a 401nm laser beam, as well as progress towards laser cooling both species. The system will \quad be used to study few- and many body physics, including collisional studies of Er-K mixtures and quantum magnetism with dipolar atoms. [Preview Abstract] |
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K1.00180: Characterizing Radiation Trapping Effects in Precision Measurements of Atomic Excited State Lifetimes Brian Patterson, Jerry Sell, Alina Gearba, Jeremiah Wells, Derald Madson, Randy Knize, Stephen Spicklemire Measurements of atomic excited state lifetimes provide a valuable test of atomic theory, allowing comparisons between experimental and theoretical transition dipole matrix elements. We previously measured the 6$P_{\mathrm{3/2\thinspace }}$state lifetime in Cs using a pulsed laser technique$^{\mathrm{1}}$, achieving a precision of 0.15{\%}. In that experiment, a single pulse from a mode-locked laser was used to excite cesium atoms in a thermal beam, and a subsequent pulse ionized the excited atoms. The ions were collected while varying the time delay between the excitation and ionization pulses. Two of the dominant systematic errors in the measurement included the effects of quantum beating and radiation trapping. We will present our recent efforts to reduce these systematic errors in lifetime measurements of the 5$P_{\mathrm{3/2\thinspace }}$state of rubidium. These efforts include using a gated CW laser to excite a single hyperfine level, greatly reducing quantum beats. We are also carrying out independent measurements of the atom beam density to better quantify the effects of radiation trapping on the measured lifetime. We use two-photon ionization of the atom beam and the known rubidium two-photon ionization cross-section to extract the rubidium density. Measurements of the Rb lifetime at various beam densities are compared to predictions of Monte Carlo calculations of the radiation trapping. $^{\mathrm{1}}$B. M. Patterson \textit{et al}., Phys. Rev. A 91, 012506 (2015). ~~~~~~~ [Preview Abstract] |
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K1.00181: Anomalies in QED corrections to the 3d states of K-like ions Jonathan Sapirstein, Kwok-Tsang Cheng Higher-order QED corrections to atomic energy levels from electron correlations are typically smaller in magnitudes than the lowest-order radiative corrections. However, such is not the case for the $3d$ states of K-like ions, as screened QED corrections are enhanced by interactions with the $1s-3p$ core electrons which have much larger one-loop self-energy and vacuum polarization corrections than the $3d$ valence electrons. In this work, screened vacuum polarization corrections are found to be almost two orders of magnitudes larger than the lowest-order corrections for the $3d$ ground states of K-like krypton. Similar enhancements should exist in the self-energies of these $3d$ states. [Preview Abstract] |
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K1.00182: A pulsed VUV laser for the search for the thorium-229 nuclear isomeric transition Christian Schneider, Justin Jeet, Eugene V. Tkalya, Eric R. Hudson The nucleus of thorium-229 has an exceptionally low-energy isomeric transition in the vacuum-ultraviolet (VUV) spectrum around $7.8 \pm 0.5$eV [1]. While inaccessible to standard nuclear physics techniques, there are various prospects for a laser-accessible nuclear transition. Our direct search for the transition uses thorium-doped crystals as samples. In a previous experiment [2] at the Advanced Light Source (ALS) synchrotron, LBNL, we were able to exclude a large portion of the transition lifetime-vs.-frequency region-of-interest (ROF) [3]. We will present the technical aspects of our ongoing efforts at UCLA, including a newly developed pulsed VUV laser system with wide tunability and VUV pulse energies up to $40 \mu J$/pulse, the absolute measurement of these pulse energies, and the characterization of the frequency spectrum of the pulsed laser light. A preliminary, updated exclusion region obtained with the new experimental setup will be depicted. \\[2ex] {[1]} B. R. Beck et al.: LLNL-PROC-415170 (2009)\\ {[2]} J. Jeet et al.: Phys. Rev. Lett. 114, 253001 (2015)\\ {[3]} E. V. Tkalya et al.: Phys. Rev. C 92, 054324 (2015) [Preview Abstract] |
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K1.00183: Testing quantum electrodynamics in the lowest singlet state of neutral beryllium-9 Will Williams, Carson Patterson, Alisha Vira, Bruce Hawkins We performed high precision spectroscopy on the 2s2p J=1 singlet state in neutral beryllium-9. This result serves as a test of quantum electrodynamics and as an assessment of theoretical methods used to predict the energy levels of beryllium. A frequency quadrupled titanium sapphire laser at 235 nm was used to probe a beam of atomic beryllium. The frequency was measured to high precision by stabilizing the 470 nm light out of the frequency doubler to an ultra-low expansion cavity that was calibrated using molecular tellurium lines. This experimental method allowed us to improve the precision of the energy level to which the singlet state is known by more than 3 orders of magnitude. [Preview Abstract] |
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K1.00184: Optogalvanic spectroscopy of lanthanum hyperfine structure Amanda Nelson, Jessie Hankes, Patrick Banner, Steven Olmschenk Optogalvanic spectroscopy is a sensitive technique to measure optical transitions of atoms and ions produced in a high voltage discharge. Advantages of this technique include a comparatively simple optical setup and the ability to interrogate excited state transitions. Here, we use optogalavanic spectroscopy in a hollow cathode lamp to measure the hyperfine spectrum of several transitions in lanthanum. Hyperfine coefficients are determined for the corresponding energy levels and compared to available previous measurements. [Preview Abstract] |
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K1.00185: Characterizing the perturbed 6snd series of Ytterbium using MW spectroscopy Fathima Niyaz, Thomas Gallagher The Yb 6snd Rydberg series is perturbed weakly by a doubly excited state lying between the 6s26s and 6s27d states. We have used microwave transitions between 6sns-6s(n$+$1)s and 6sns-6s(n-1)d states to determine the energies of the 6snd Rydberg states of~28$\le $n$\le $40. We have analyzed the energies if the perturbed series using quantum defect theory, which allows the characterization of the perturbed series by only four parameters. The quantum defect theory model~predicts the energies to the accuracy of a few MHz. We have also made lifetime measurements of the 6snd states as a consistency check of our analysis. This work has been supported by the Chemical Sciences Division of the Department of Energy. [Preview Abstract] |
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K1.00186: Frequency-comb based spectroscopy of the Yb I 399 nm transition Quinton McKnight, Michaela Kleinert, Scott Bergeson We determine the frequency of the Yb I $^1S_0 - ^1P_1$ transition at 399 nm using an optical frequency comb. Although this transition was measured previously using an optical transfer cavity [D. Das et al., Phys. Rev. A 72, 032506 (2005)], recent work has uncovered significant errors in that method. We compare our result with those from the literature and discuss observed differences. We verify the correctness of our method by measuring the frequencies of well-known transitions in Rb and Cs, and by demonstrating proper control of systematic errors in both laser metrology and atomic spectroscopy. We also demonstrate the effect of quantum interference due to hyperfine structure in a divalent atomic system and present isotope shift measurements for all stable isotopes. [Preview Abstract] |
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K1.00187: Predicted broad resonant absorption feature in the continuum spectrum of Ho II Werner Eissner, Sultana Nahar Ho II lines are being observed in metal poor stars. Excess of Ho II lines relative to Fe-peak elements in these stars indicate enhanced neutron-capture or the rapid or r-process in contrast to typical stars. However due to high line blending, spectroscopic identification of the observed lines have been difficult. We have carried out atomic structure calculations from bound-bound and bound-free transitions in Ho II (Z=67) in relativistic Breit-Pauli approximation using the program SUPERSTRUCTURE. However, the objective is to study the features in the continuum, particularly due to strong 4d-4f transitions in $4s^24p^64d^{10}5s^25p^66s4f^{11}$). We find that there are extensive number, a total of 6712, 4d-4f allowed E1 transitions which form an enhanced broad resonant structure in the energy region of 150 - 200 eV. The feature is expected to be observable in the absorption spectrum of Ho II. [Preview Abstract] |
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K1.00188: Precise lifetime of the metastable $^{\mathrm{2}}$P$_{\mathrm{1/2}}$ state in Ar$^{\mathrm{9+}}$ ions isolated in a Penning trap Joseph Tan, Samuel Brewer, Joan Dreiling, Shannon Hoogerheide, Nicholas Guise, Aung Naing A measurement with \textless 1{\%} statistical uncertainty is presented for the radiative decay lifetime of the metastable $^{\mathrm{2}}$P$_{\mathrm{1/2}}$ state in the ground-state fine structure of fluorine-like Ar$^{\mathrm{9+}}$ (one hole in the filled 2$p$ subshell). The method involves the extraction of multiply-ionized Ar atoms from an electron beam ion trap (EBIT) and the capture of only Ar$^{\mathrm{9+}}$ ions in a compact Penning trap. The $^{\mathrm{2}}$P$_{\mathrm{1/2}}$ state of the stored Ar$^{\mathrm{9+}}$ ions can spontaneously decay via M1 (spin-flip) radiative transition to the ground state, with the photon emission monitored using a photomultiplier tube and a multichannel scaler. Improvements that reduced measurement uncertainty are discussed. The results are compared with theory and prior measurements. [Preview Abstract] |
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K1.00189: Observation and analysis of high-lying singlet gerade states of rubidium dimer Phillip Arndt, Xinhua Pan, David Beecher, Marjatta Lyyra, Ergin Ahmed The structure of the excited electronic states of Rubidium dimer is important to a number of areas of research including, the production of ultracold ground state molecules, cold atom-molecule collisions, and the development of new \textit{ab-initio} molecular electronic structure methods. In the experiment we used optical double resonance technique to observe large number of ro-vibrational levels of the 5$^{\mathrm{1}}\Sigma _{\mathrm{g}}^{\mathrm{+}}$, 6$^{\mathrm{1}}\Sigma _{\mathrm{g}}^{\mathrm{+}}$, and 3$^{\mathrm{1}}\Pi_{\mathrm{g}}$ electronic states in the 24000-26000 cm$^{\mathrm{-1}}$ range. The Rb$_{\mathrm{2}}$ molecules were initially excited from the ground X$^{\mathrm{1}}\Sigma_{\mathrm{g}}^{\mathrm{+}}$ state to an intermediate level of the mixed A$^{\mathrm{1}}\Sigma _{\mathrm{u}}^{\mathrm{+}}$\textasciitilde b$^{\mathrm{3}}\Pi _{\mathrm{u}}$ manifold using a narrow band tunable TiSa laser. In the next step the probe laser, a narrow band dye laser tunable in the 13000-14000cm$^{\mathrm{-1\thinspace }}$range, excited the molecules further to the target states. The resonances of the probe laser were observed by detecting the total fluorescence from the excited states to the a$^{\mathrm{3}}\Sigma_{\mathrm{u}}^{\mathrm{+}}$ state in the 500nm range. Potential energy curve was constructed for each state from the term values of the observed levels. [Preview Abstract] |
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K1.00190: Computing Rydberg Electron Transport Rates Using Periodic Orbits Sulimon Sattari, Kevin Mitchel Electron transport rates in chaotic atomic systems are computable from classical periodic orbits. This technique allows for replacing a Monte Carlo simulation launching millions of orbits with a sum over tens or hundreds of properly chosen periodic orbits using a formula called the spectral determiant. A firm grasp of the structure of the periodic orbits is required to obtain accurate transport rates. We apply a technique called homotopic lobe dynamics (HLD) to understand the structure of periodic orbits to compute the ionization rate in a classically chaotic atomic system, namely the hydrogen atom in strong parallel electric and magnetic fields. HLD uses information encoded in the intersections of stable and unstable manifolds of a few orbits to compute relevant periodic orbits in the system. All unstable periodic orbits are computed up to a given period, and the ionization rate computed from periodic orbits converges exponentially to the true value as a function of the period used. Using periodic orbit continuation, the ionization rate is computed over a range of electron energy and magnetic field values. The future goal of this work is to semiclassically compute quantum resonances using periodic orbits. [Preview Abstract] |
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