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 J9: Atomic Clocks |
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Chair: Samuel Brewer, NIST Room: 315 |
Wednesday, June 7, 2017 2:00PM - 2:12PM |
J9.00001: A Fermi-degenerate three-dimensional optical lattice clock Ross Hutson, Sara Campbell, Edward Marti, Akihisa Goban, Wei Zhang, John Robinson, Lindsay Sonderhouse, Jun Ye Ongoing advances in atomic clocks enable table top searches of dark matter and other physics beyond the Standard Model. Currently the most accurate and stable clocks are based on alkaline-earth(-like) neutral atoms confined to one-dimensional optical lattices. A major obstacle in improving clock stability and accuracy is mitigating density-dependent frequency shifts due to contact interactions. We overcome this limitation by loading a two spin component degenerate Fermi gas of strontium atoms into a three-dimensional optical lattice. By tuning the thermal, kinetic, and interaction energy scales, we operate in the half-filled Mott insulating regime that suppresses atomic collisions and leaves and any residual contact interactions spectroscopically resolvable. Additionally, we demonstrate control of the scalar, vector, and tensor components of the three-dimensional lattice induced ac Stark shifts, enabling the observation of a 6 second atom-light coherence time. [Preview Abstract] |
Wednesday, June 7, 2017 2:12PM - 2:24PM |
J9.00002: Feasibility of hollow core fiber based optical lattice clock Ekaterina Ilinova, James F. Babb, Andrei Derevianko The possibility of building the optical lattice clock based on the narrow $^1S_0$-$^3P_0$ transition in Hg and other alkaline-earth like atoms optically trapped inside the hollow core fiber has been studied. The general form of the long range atom-surface interaction potential at non-zero temperatures has been calculated for the hollow capillary geometry. The resulting $^1S_0$-$^3P_0$ transition frequency shift has been calculated for Sr and Hg atoms as a function of their position inside the capillary. Its dependence on the geometric parameters and optical properties of the capillary material has been analyzed. The resonant enhancement of the atom-surface interaction potential and radiative decay rate of the $^3P_0$ state at certain parameters of the waveguide has been studied. For the silica capillary with inner radius $R_{in}>15$ $\mu m$ and thickness $d\sim 1$ $\mu m$ the atom surface interaction induced $^1S_0$-$^3P_0$ transition frequency shift on the capillary axis can be suppressed down to the level $\delta \nu/\nu<10^{-18}$. The additional frequency shifts and atom loss from the optical trap due to the residual birefringence of the waveguide and collisions with the buffer gas molecules have been evaluated. [Preview Abstract] |
Wednesday, June 7, 2017 2:24PM - 2:36PM |
J9.00003: A new approach to an accurate calculation of hyperpolarizabilities Sergey Porsev, Marianna Safronova, Ulyana Safronova, Mikhail Kozlov A systematic effect that yet to be addressed to further reduce uncertainty of optical atomic clocks is a lattice Stark shift caused by the term nonlinear in lattice intensity and determined by the hyperpolarizability. Due to complexity of the theoretical expression for this quantity no reliable calculations of hyperpolarizabilities are available even for simpler atoms and ions than used for clock applications. We have developed a new approach to calculate hyperpolarizabilities for atoms and ions based on a solution of the inhomogeneous equation, what allows us very effectively and accurately carry out summations over intermediate states. We applied our new method to the calculation of the hyperpolarizabilities for the $^1\!S_0$ and $^3\!P_0$ clock states in Sr and Yb. The results will be reported at the conference. [Preview Abstract] |
Wednesday, June 7, 2017 2:36PM - 2:48PM |
J9.00004: Hyperpolarizability and operational magic wavelength in an optical lattice clock R Brown, N. Phillips, K. Beloy, W. McGrew, M. Schioppo, R. Fasano, X. Zhang, H. Leopardi, D. Nicolodi, T. Fortier, A. Ludlow One of the largest systematic frequency shifts in optical lattice clocks arises from light shifts due to the trapping lattice. At the 1x10\textasciicircum -18 level we find that light shift effects beyond the dominant electric dipole coupling (hyperpolarizability, magnetic dipole, and electric quadrupole) become relevant. Including finite temperature effects, we observe a simple linear $+$ quadratic scaling of clock frequency shift with trap depth. For any choice of trap depth, we may tune our trapping laser to a corresponding ``operational magic wavelength'' where the clock shift is insensitive to uncontrolled changes in trap depth. We further explore atomic temperature-dependent effects by implementing a third stage of quenched sideband laser cooling on the ultra-narrow $^{\mathrm{1}}$S$_{\mathrm{0}}$ to $^{\mathrm{3}}$P$_{\mathrm{0}}$ clock transition. This cooling allows us to achieve near unit occupation of the ground band of our 1-D optical lattice (corresponding to temperatures in the 100's of nK) within a few 10's of ms. This cooling implies increased atomic confinement, which we use as a lever arm to explore previously unobservable magnetic dipole and electric quadrupole effects. [Preview Abstract] |
Wednesday, June 7, 2017 2:48PM - 3:00PM |
J9.00005: Searching for Dark Matter and Exotic Physics with Atomic Clocks and the GPS Constellation Benjamin Roberts, Geoffrey Blewitt, Conner Dailey, Maxim Pospelov, Alex Rollings, Jeff Sherman, Wyatt Williams, Andrei Derevianko Cosmological observations indicate that dark matter (DM) constitutes 85\% of all matter in the Universe, yet conclusive evidence for DM in terrestrial experiments remains elusive. One of the possibilities is that DM can be composed from ultralight quantum fields whose self-interactions lead to the formation of DM objects in the form of stable topological defects. As the Earth moves through the halo of DM objects, interactions with such DM clumps could lead to measurable variations in GPS signals which propagate through the satellite constellation at galactic velocities. We use the network of atomic clocks onboard GPS satellites as a 50000\,km aperture DM detector. By mining over 16yr of archival GPS data, we find no evidence for topological defects in the form of domain walls at our current sensitivity, which enables us to improve the present limits on certain DM--ordinary matter coupling strengths by up to six orders of magnitude.\\~\\ [1] A. Derevianko and M. Pospelov, Nat. Phys. 10, 933 (2014) [Preview Abstract] |
Wednesday, June 7, 2017 3:00PM - 3:12PM |
J9.00006: Experimental research of good-bad cavity dual-wavelength active optical clock Jingbiao Chen, Duo Pan, Biao Xue, Tiantian Shi The stability of clock laser for optical clocks is currently limited by the cavity-length noise of the super cavity, which is induced by the thermal Brownian-motion. The active optical clock, first proposed in 2005, has dramatically reduced the sensibility of the output frequency to the cavity-length noise, nevertheless, the stability is still limited by the residual cavity pulling effect. To stabilize the main cavity length, we propose a dual- wavelength active optical clock, of which the two output lasers with different wavelength share the same cavity, and work in good cavity regime at YAG 1064 nm and bad cavity regime at Cs 1470 nm, respectively. The good cavity signal is locked to a super cavity by the PDH technique, and thus the main cavity length of the active optical clock is stabilized. The frequency stability of the active optical clock signal is expected to be improved by 2 orders of magnitude than that of the PDH stabilized signal, due to the suppression of cavity pulling effect in the bad cavity. Experimentally, we realize the dual-wavelength output of the active optical clock, and the power and linewidth characteristics are preliminarily studied. In the next step, we will work on the PDH stabilization of the bad cavity signal. [Preview Abstract] |
Wednesday, June 7, 2017 3:12PM - 3:24PM |
J9.00007: Study of high SNR Ramsey-CPT spectrum with dispersion detection in Rb cell Xiaolin Sun, Pengfei Cheng, Chi Xu, Lu Zhao, Jianwei Zhang, Lijun Wang For the traditional circularly polarized pumping schemes in coherent population trapping (CPT), numerous atoms are trapped in the extreme Zeeman states that do not contribute to the magnetic insensitive 0-0 clock transition, thus resulting in small CPT signal amplitude. Here we report that the lin-par-lin Ramsey-CPT configuration with dispersion detection can obtain a high-contrast signal and keep the system compact. The dispersion detection method by orthogonal polarizers can effectively suppress background optical noise, which further improves the signal-to-noise ratio (SNR) of the Ramsey spectrum. We theoretically and experimentally investigate the SNR of the Ramsey spectrum signal by varying the relative angle of the polarizer and analyzer as well as the applied static magnetic field. The theoretical calculations agree with the experimental results very well, and the optimized working parameters of the relative angle and magnetic field are obtained. According to the optimized working parameters, the short-term frequency stability of the Rb clock is estimated to be 6.6E-13$\tau$$^-1/2$. As we can see, this kind of atomic clock is very promising for the development of compact, high-performance vapor clock based on CPT. [Preview Abstract] |
Wednesday, June 7, 2017 3:24PM - 3:36PM |
J9.00008: Power scaling of extreme ultraviolet frequency combs to the mW level per high harmonic Gil Porat, Christoph M. Heyl, Stephen B. Schoun, Craig Benko, Nadine Dorre, Kristan Corwin, Jun Ye Recently, a demonstration of direct frequency comb spectroscopy in the extreme ultraviolet (XUV) has been performed, however further advancement is curtailed due to the limited XUV comb power of $\sim$0.2 mW per harmonic. The method for generating XUV combs is via intracavity high harmonic generation (HHG). The main challenge for further power scaling of XUV comb is the detrimental effect of plasma, generated in the HHG process, on intracavity power buildup and on phase-matching. Due to the laser`s high repetition rate, this plasma has a cumulative effect over multiple pulses as each production takes much longer than the $<$10ns interval between pulses to clear the generation volume. We address the steady-state plasma problem by adding a light carrier gas (helium) to a heavy generation gas (xenon). This increases the gas jet forward velocity, thus reducing the number of intracavity laser pulses that interact with the same atom/ion. Furthermore, we experimentally demonstrate that by increasing the time between consecutive pulses, while keeping the same intensity, the HHG conversion efficiency per pulse is enhanced. This is an indication of improved phase-matching, making phase-matched intracavity HHG possible. We have achieved record powers of 1.2 mW at 97 nm and 0.53 mW at 63 nm. [Preview Abstract] |
Wednesday, June 7, 2017 3:36PM - 3:48PM |
J9.00009: Heisenberg-limited Rabi spectroscopy in decoherence free subspaces Tom Manovitz, Ravid Shaniv, Nitzan Akerman, Yotam Shapira, Roee Ozeri One of the techniques for suppressing noise in quantum systems is through the use of decoherence free subspaces (DFSs). A quantum state can be engineered so that it resides in a subspace which is degenerate with respect to the primary noise operators. Any operation performed on the qubits which remains within this subspace is immune to the damages of decoherence. In this work we entangled two ions in a Paul trap in order to create a correlated measurement of their internal atomic transition while in a DFS. We generate an effective $\sigma_{x}\sigma_{x}+\delta\sum\sigma_{z}$ Hamiltonian and scan the detuning $\delta$ through the transition resonance, observing a Rabi-spectroscopy peak twice as narrow as the single-ion case. Such an interaction Hamiltonian acts separately on two orthogonal subspaces corresponding to the mean and differential transition frequency of the ions, separating the Hilbert space into two DFSs. Hence, one can measure the differential frequency while remaining immune to decohering mean frequency noise, and vice versa. Furthermore, the narrowing we observed due to the entangling Hamiltonian produces a Rabi spectroscopy measurement which is limited by the energy-time Heisenberg uncertainty relation, previously only demonstrated using Ramsey spectroscopy. [Preview Abstract] |
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