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 P9: Advances in atom interferometry |
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Chair: Paul Hamilton, UCLA Room: 315 |
Thursday, June 8, 2017 2:00PM - 2:12PM |
P9.00001: Gravity sensing using Very Long Baseline Atom Interferometry Dennis Schlippert, \'Etienne Wodey, Christian Meiners, Dorothee Tell, Christian Schubert, Wolfgang Ertmer, Ernst M. Rasel Very Long Baseline Atom Interferometry (VLBAI) has applications in high-accuracy absolute gravimetry, gravity-gradiometry, and for tests of fundamental physics. Thanks to the quadratic scaling of the phase shift with increasing free evolution time, extending the baseline of atomic gravimeters from tens of centimeters to meters puts resolutions of $10^{-13}$\,g and beyond in reach. We present the design and progress of key elements of the VLBAI-test stand: a dual-species source of Rb and Yb, a high-performance two-layer magnetic shield, and an active vibration isolation system allowing for unprecedented stability of the mirror acting as an inertial reference. We envisage a vibration-limited short-term sensitivity to gravitational acceleration of $1\cdot 10^{-8}$ m/s$^2/$Hz$^{1/2}$ and up to a factor of 25 improvement when including additional correlation with a broadband seismometer. Here, the supreme long-term stability of atomic gravity sensors opens the route towards competition with superconducting gravimeters. The operation of VLBAI as a differential dual-species gravimeter using ultracold mixtures of Yb and Rb atoms enables quantum tests of the universality of free fall (UFF) at an unprecedented level of $\le 10^{-13}$, potentially surpassing the best experiments to date. [Preview Abstract] |
Thursday, June 8, 2017 2:12PM - 2:24PM |
P9.00002: Mach-Zehnder atom interferometer inside an optical fiber. Mingjie Xin, Wuiseng Leong, Zilong Chen, Shau-Yu Lan Precision measurement with light-pulse grating atom interferometry in free space have been used in the study of fundamental physics and applications in inertial sensing. Recent development of photonic band-gap fibers allows light for traveling in hollow region while preserving its fundamental Gaussian mode. The fibers could provide a very promising platform to transfer cold atoms. Optically guided matter waves inside a hollow-core photonic band-gap fiber can mitigate diffraction limit problem and has the potential to bring research in the field of atomic sensing and precision measurement to the next level of compactness and accuracy. Here, we will show our experimental progress towards an atom interferometer in optical fibers. We designed an atom trapping scheme inside a hollow-core photonic band-gap fiber to create an optical guided matter waves system, and studied the coherence properties of Rubidium atoms in this optical guided system. We also demonstrate a Mach-Zehnder atom interferometer in the optical waveguide. This interferometer is promising for precision measurements and designs of mobile atomic sensors. [Preview Abstract] |
Thursday, June 8, 2017 2:24PM - 2:36PM |
P9.00003: Recoil-sensitive lithium interferometer without a subrecoil sample Kayleigh Cassella, Eric Copenhaver, Brian Estey, Yanying Feng, Chen Lai, Holger M\"uller We report recoil-sensitive Ramsey-Bord\'{e} atom interferometry with a sample of lithium-7 atoms at 300 $\mu K$, well above the atomic recoil temperature of 6 $\mu K$. We overcome the need for additional cooling and velocity selection steps, which decrease phase sensitivity, by spectrally resolving the output ports with 160-ns Raman beam splitters. The large bandwidth pulses drive both conjugate interferometers simultaneously with nearly equal contrast, allowing for state selective detection of the summed interferometer signal. Optical pumping to a magnetically-insensitive state suppresses magnetic dephasing and extends coherence time. Sensitivity comparable to interferometers using large momentum transfer pulses can be attained at interrogation times on the order of 10-ms due to lithium’s high recoil frequency and the increased available atom number. At this time scale, vibration noise is converted to amplitude noise and does not perturb the determination of the recoil frequency from the summed interference signal. In addition to simplifying cooling, increasing atom number and reducing cycle time for faster integration, these techniques broaden the applicability of recoil-sensitive interferometry to particles that remain difficult to trap and cool, like electrons. [Preview Abstract] |
Thursday, June 8, 2017 2:36PM - 2:48PM |
P9.00004: Large momentum transfer atomic interferometric gyroscope Robert Compton, Joshua Dorr, Karl Nelson, Richard Parker, Brian Estey, Holger M\"uller Atom interferometry~holds out significant promise as the basis for compact, low cost, high performance inertial sensing.~ Some light pulse atom interferometers are based on an atomic beam-splitter in which the interferometer paths separate at the velocity imparted by a two-photon (Raman) recoil event, resulting in narrow path separation and a corresponding high aspect ratio between the length and width of the interferometer.~ In contrast, proposals for large momentum transfer (LMT) offer paths to larger separation between interferometer arms, and aspect ratios approaching 1.~ Here, we demonstrate an LMT gyroscope based on a combination of~Bragg and Bloch atomic transitions adding up to a total of 8 photons of momentum transfer.~ We discuss prospects for scalability to larger photon numbers where angular random walk (ARW) can be better than navigation-grade. [Preview Abstract] |
Thursday, June 8, 2017 2:48PM - 3:00PM |
P9.00005: Symmetric large momentum transfer for atom interferometry with BECs Sven Abend, Martina Gebbe, Matthias Gersemann, Ernst M. Rasel We develop and demonstrate a novel scheme for a symmetric large momentum transfer beam splitter for interferometry with Bose-Einstein condensates. Large momentum transfer beam splitters are a key technique to enhance the scaling factor and sensitivity of an atom interferometer and to create largely delocalized superposition states. To realize the beam splitter, double Bragg diffraction is used to create a superposition of two symmetric momentum states. Afterwards both momentum states are loaded into a retro-reflected optical lattice and accelerated by Bloch oscillations on opposite directions, keeping the initial symmetry. The favorable scaling behavior of this symmetric acceleration, allows to transfer more than 1000 $\hbar k$ of total differential splitting in a single acceleration sequence of 6 ms duration while we still maintain a fraction of approx. 25\% of the initial atom number. As a proof of the coherence of this beam splitter, contrast in a closed Mach-Zehnder atom interferometer has been observed with up to 208 $\hbar k$ of momentum separation, which equals a differential wave-packet velocity of approx. 1.1 m/s for $^{87}$Rb. [Preview Abstract] |
Thursday, June 8, 2017 3:00PM - 3:12PM |
P9.00006: Techniques for Macroscopic Scale Atom Interferometry Tim Kovachy, Peter Asenbaum, Chris Overstreet, Jason Hogan, Mark Kasevich Atom interferometers that cover macroscopic scales in space and in time have a high intrinsic sensitivity to inertial forces, making them a valuable tool for a wide range of applications. We have used such interferometers in a 10 meter atomic fountain apparatus for precision gravity gradiometry, measurements of phase shifts associated with spacetime curvature across a single quantum system, and differential acceleration measurements between Rb-85 and Rb-87 for a test of the weak equivalence principle. This talk will focus on the techniques that enable these large scale interferometers, with path separations of tens of centimeters and durations of more than a second. As the path separation and duration are increased, the interferometer becomes more susceptible to experimental imperfections that degrade the interference signal. We will describe how this challenge can be overcome through the use of large momentum transfer atom optics based on sequential two-photon Bragg transitions, high power atom optics lasers with a spectrum that compensates unwanted light shifts, and magnetic/optical-dipole lensing to produce a well-collimated atom source. [Preview Abstract] |
Thursday, June 8, 2017 3:12PM - 3:24PM |
P9.00007: Opportunities for Maturing Precision Metrology with Ultracold Gas Studies Aboard the ISS Jason Williams, Jose D'Incao Precision atom interferometers (AI) in space are expected to become an enabling technology for future fundamental physics research, with proposals including unprecedented tests of the validity of the weak equivalence principle, measurements of the fine structure and gravitational constants, and detection of gravity waves and dark matter/dark energy. We will discuss our preparation at JPL to use NASA's Cold Atom Lab facility (CAL) to mature the technology of precision, space-based, AIs. The focus of our flight project is three-fold: a) study the controlled dynamics of heteronuclear Feshbach molecules, at temperatures of nano-Kelvins or below, as a means to overcome uncontrolled density-profile-dependent shifts in differential AIs, b) demonstrate unprecedented atom-photon coherence times with spatially constrained AIs, c) use the imaging capabilities of CAL to detect and analyze spatial fringe patterns written onto the clouds after AI and thereby measure the rotational noise of the ISS. The impact from this work, and potential for follow-on studies, will also be reviewed in the context of future space-based fundamental physics missions. [Preview Abstract] |
Thursday, June 8, 2017 3:24PM - 3:36PM |
P9.00008: Competition between spin echo and spin self-rephasing in a trapped atom interferometer Xavier Alauze, Alexis Bonnin, Franck Pereira Dos Santos, Cyrille Solaro, Jean-Noel Fuchs, Frederic Combes, Frederic Piéchon The FORCA-G project aims to develop a quantum sensor to probe short range forces. We realize a trapped atom interferometer of $^{87}$Rb in a vertical optical lattice in which stimulated Raman transitions induce coherent coupling between adjacent lattice sites. We thus measure the Bloch frequency with a state-of-the-art relative sensitivity of 1.8 10$^{-6}$ at 1s. Optical evaporative cooling allows us to increase the density and thus the number of atoms per well. We studied in a recent work the impact of atomic interactions at densities of a few 10$^{12}$ atoms/cm$^3$. We observe, in the dipolar trap, an unexpected behaviour of the contrast, when applying a $\pi$-pulse to symmetrize the interferometer. These results are interpreted as a competition between the spin-echo technique and a spin self-rephasing (SSR) mechanism based on identical spin rotation effect (ISRE) . Originating from particle indistinguishability, SSR is a remarkable mechanism that can enhance the clock's coherence up to several tens of seconds. This illustrates the important role of atomic interactions, in quantum sensors based on trapped ultracold atomic ensembles. They can lead to complex and non-intuitive dynamics of the system, either detrimental or favorable depending on the interferometer configuration. [Preview Abstract] |
Thursday, June 8, 2017 3:36PM - 3:48PM |
P9.00009: Decoherence in Ramsey Spectroscopy Due to Magnetic Field Gradients Frank Narducci, Arvind Srinivasan, Jon P. Davis, Matthias Zimmermann, Maxim Efremov, Ernst Rasel, Wolfgang Schleich Ramsey or spin-echo spectroscopy techniques are often used to interferometrically probe systems. Most experiments use the the `clock’ transition to suppress the sensitivity to magnetic fields. Magnetic Raman transitions will behave the same way as the clock transition, apart from a dependence of the resonance frequency on the value of the field for perfectly static and uniform magnetic fields. However, our current experiments require the presence of a magnetic field gradient. The magnetic field gradient causes a loss of contrast in the interference pattern in two ways. Due to the gradient and the spatial extend of the cloud, the resonance frequency of the transition differs between atoms such that they do not receive perfect $\pi/2$ pulses. Proper frequency chirping of the Raman fields can restored the peak Raman amplitude. Secondly, the precession rate differs between different atoms, which is not reversible by standard spin echo techniques. This dephasing can be interpreted as a result of the non-closure of the interferometer. A properly closed interferometer, such as the one we demonstrate with a four pulse sequence will restore the contrast. We apply our results to our experiments on the measurement of the $T^3$ contribution to the phase of the interferometer. [Preview Abstract] |
Thursday, June 8, 2017 3:48PM - 4:00PM |
P9.00010: Atom-optics knife-edge: Measuring sub-nanokelvin momentum distributions Ramon Ramos, David Spierings, Aephraim Steinberg Temperatures below 1 nanokelvin have been achieved in the recent years, enabling new classes of experiments which benefit from the resulting long coherence times. This achievement comes hand in hand with the challenge of measuring such low temperatures. By employing the equivalent of a knife-edge measurement for matter-waves, we have been able to characterize ultra-low momentum widths. We measured a momentum width corresponding to an effective temperature of 900 $\pm$ 200 pK, only limited by our cooling performance. We show that this technique compares favourably with more traditional methods, which would require expansion times of 100’s of ms or frequency stability of 10’s of Hz. Finally, we show that the effective knife-edge, created by a potential barrier, begins to become ``blunt" due to tunneling for thin barriers, and we obtain quantitative agreement with a theoretical model. This method is a useful tool for atomic interferometry and other areas in ultracold atoms where a robust and precise technique for characterizing the momentum distribution is required. [Preview Abstract] |
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