Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session M8: Atomic Clocks |
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Sponsoring Units: GPMFC Chair: Elizabeth Donley, National Institute of Technology Room: Franklin CD |
Thursday, June 11, 2015 8:00AM - 8:12AM |
M8.00001: 2e-18 total uncertainty in an atomic clock Travis Nicholson, Sara Campbell, Ross Hutson, George Marti, Benjamin Bloom, Rees McNally, Wei Zhang, Murray Barrett, Marianna Safronova, Gregory Strouse, Weston Tew, Jun Ye The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, new insights in quantum science, tighter limits on fundamental constant variation, and improved tests of relativity. We present an important step towards realizing the full potential of a many-particle clock with a state-of-the-art stable laser. Here, we achieve stability of 2.2e-16 at 1 s by using seconds-long coherent interrogations of our clock transition. With this better stability, we perform a new accuracy evaluation of our clock. For the lattice ac Stark systematic, we identify the lattice laser frequency where the scalar and tensor components of the shift cancel, allowing for state independent trapping with clock shifts at the 1e-18 level. For the BBR systematic, we improve our measurement of the atoms' thermal environment using accurate radiation thermometry traceable to the NIST ITS-90 absolute temperature scale. We also directly measure the component of the strontium atomic structure that is chiefly responsible for the spectral response to room-temperature BBR. Our combined measurements have reduced the total uncertainty of the JILA Sr clock to a record 2.1e-18. [Preview Abstract] |
Thursday, June 11, 2015 8:12AM - 8:24AM |
M8.00002: Progress toward a spin squeezed optical atomic clock beyond the standard quantum limit Boris Braverman, Akio Kawasaki, Vladan Vuletic State of the art optical lattice atomic clocks have reached a relative inaccuracy level of $10^{-18}$, already making them the most stable time references in existence. One restriction on the precision of these clocks is the projection noise caused by the measurement of the atomic state. This limit, known as the standard quantum limit (SQL), can be overcome by entangling the atoms. By performing spin squeezing, it is possible to robustly generate such entanglement and therefore surpass the SQL of precision in optical atomic clocks. I will report on recent experimental progress toward realizing spin squeezing in an ${}^{171}$Yb optical lattice clock. A high-finesse micromirror-based optical cavity mediates the atom-atom interaction necessary for generating the entanglement. By exceeding the SQL in this state of the art system, we are aiming to advance precision time metrology, as well as expanding the boundaries of quantum control and measurement. [Preview Abstract] |
Thursday, June 11, 2015 8:24AM - 8:36AM |
M8.00003: A Superradiant Laser in Strontium Matthew Norcia, Matthew Winchester, James Thompson An ensemble of Alkaline Earth atoms cooled and trapped in an optical lattice has been proposed as a gain medium for a very narrow (mHz) linewidth laser. This laser would operate in a bad-cavity regime, where the linewidth of the lasing transition is much narrower than that of the cavity that surrounds it. In this regime, perturbations of the lasing frequency due to shifts in cavity frequency are highly suppressed. I will present experimental progress towards the realization of such a laser based on Strontium atoms. [Preview Abstract] |
Thursday, June 11, 2015 8:36AM - 8:48AM |
M8.00004: Coherent Population Trapping Based Collective State Atomic Clock Using Trapped Atoms May E. Kim, Renpeng Fang, Resham Sarkar, Selim M. Shahriar In most atomic clocks, the signal collection efficiency is limited to only a few percent due to unavoidable geometric constraints, which limits its stability. We describe a coherent population trapping (CPT) based atomic clock that can achieve a much higher collection efficiency, and has reduction in linewidth by factor of $\sqrt{N}$, where $N$ is number of atoms. The CPT process pumps atoms into dark state, $|-\rangle$, which is a superposition of two atomic states. When all atoms are in $|-\rangle$, the system is in collective state $|E_D\rangle=|-,-,-,...-\rangle$. The signal corresponding to measurement of $|E_D\rangle$ has resonance that is narrowed by $\sqrt{N}$ compared to the width in conventional CPT clock. This narrowing results from interference among collective states, and can be interpreted as manifestation of effective increase in clock frequency by $\sqrt{N}$. The amplitude of $|E_D\rangle$ can be observed via null measurement of bright state $|+\rangle$. When no fluorescence from $|+\rangle$ is detected, the system is in $|E_D\rangle$. By coherent Raman scattering of anti-Stokes photons in an optically dense cloud of cold atoms, the collection efficiency approaches unity, which improves clock stability significantly, leading to advance in precision time keeping. [Preview Abstract] |
Thursday, June 11, 2015 8:48AM - 9:00AM |
M8.00005: Solar oscillations and the search for Venus enabled by a laser frequency comb David F. Phillips, Alexander G. Glenday, Chih-Hao Li, Nicholas Langellier, Guoqing Chang, Gabor Furesz, Franz X. Kaertner, Dimitar Sasselov, Andrew Szentgyorgyi, Ronald L. Walsworth We have recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple, home-built solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope calibrated with our green astro-comb. The green astro-comb is a laser frequency comb optimized for calibrating astrophysical spectrographs. We plan, in the coming year, to use the astro-comb calibrated spectrograph and solar telescope to detect the solar RV signal induced by Venus and thus demonstrate sensitivity of these instruments to detect terrestrial exoplanets. Here, we will present the astro-comb, results from the astro-comb calibrating the HARPS-N exoplanet searcher spectrograph, solar RV stability and plans for observing the signature of Venus. [Preview Abstract] |
Thursday, June 11, 2015 9:00AM - 9:12AM |
M8.00006: Spectroscopy of the forbidden $^1S_0 \rightarrow \,^3P_0$ transition on ultra-cold ytterbium atoms Alexandre Dareau, Matthias Scholl, Quentin Beaufils, Daniel D\"{o}ring, J\'{e}r\^{o}me Beugnon, Fabrice Gerbier Cold atoms in optical lattices are often considered a rich playground for emulating condensed matter systems, since they make it possible to engineer many-body Hamiltonians with tunable parameters. However, one missing feature is the ability to emulate orbital magnetism. Recent proposals for simulating orbital magnetism with neutral atoms rely on a state-dependent optical lattice with laser-driven hopping.\footnote{D. Jaksch and P. Zoller, NJP \textbf{5}, 56 (03)}$^,$\footnote{F. Gerbier and J. Dalibard, NJP \textbf{12}, 033007 (10)} Ytterbium, with its long lived metastable state ($^3P_0$), is a well-suited candidate for the implementation of such schemes. Addressing the forbidden transition between ytterbium ground ($^1S_0$) and meta-stable ($^3P_0$) states is experimentally challenging, and requires the use of a laser with stability close to the standards of atomic clocks. I will report on the building of a ultra-narrow laser locked on a high-finesse low-expansion cavity.\footnote{Dareau \textit{et al.}, arXiv:1412.5751} I will then show how the absolute frequency of the cavity modes can be calibrated by performing high-resolution spectroscopy on molecular iodine, allowing us perform Doppler spectroscopy on the $^1S_0\rightarrow\,^3P_0$ transition of an ytterbium BEC. [Preview Abstract] |
Thursday, June 11, 2015 9:12AM - 9:24AM |
M8.00007: Clocks and superpositions of proper time -- Post-Newtonian effects in quantum mechanics Igor Pikovski, Magdalena Zych, Fabio Costa, Caslav Brukner Phenomena inherent to quantum theory on curved space-time are typically assumed to be only relevant at extreme physical conditions: at high energies and in strong gravitational fields. Here we consider low-energy quantum mechanics in the presence of weak gravitational time dilation and show that the latter leads to novel phenomena that can be probed in experiments. We study a quantum version of the ``twin paradox'' in which a system is brought in superposition of being at two different gravitational potentials, and show that time dilation induces entanglement between internal degrees of freedom and the center-of-mass of a composite particle. The effect of general relativistic time dilation on a quantum wave function can thus be probed in optical or matter-wave interferometry. In addition, we derive that time dilation causes universal decoherence of all composite quantum systems and thus causes the transition to classicality for microscale systems. Our results show that the interplay between quantum theory and general relativity offers novel phenomena and that such a regime can be accessed with quantum optical experiments. [Preview Abstract] |
Thursday, June 11, 2015 9:24AM - 9:36AM |
M8.00008: Lutetium$+$: A better clock candidate Kyle Arnold, Eduardo Paez, Elnur Haciyev, Arifin Arifin, Radu Cazan, Murray Barrett With the extreme precision now reached by optical clocks it is reasonable to consider redefinition of the frequency standard. In doing so it is important to look beyond the current best-case efforts and have an eye on future possibilities. We will argue that singly ionized Lutetium is a strong candidate for the next generation of optical frequency standards. Lu$+$ has a particularly narrow optical transition in combination with several advantageous properties for managing systematic uncertainties compared to the other atomic species. We summarize these properties and our specific strategies for managing the uncertainties due to external perturbations. Finally, we present the status of our ongoing experiments with trapped Lu$+$, including the results of precision measurements of its atomic structure. [Preview Abstract] |
Thursday, June 11, 2015 9:36AM - 9:48AM |
M8.00009: Precision Measurements of Quantum Scattering Phase Shifts through Feshbach Resonances Aaron Bennett, Kurt Gibble We present precision measurements of quantum scattering phase shifts through a series of Feshbach resonances. Using an atomic fountain clock, we scatter ultracold cesium atoms in a coherent superposition of the clock states off target atoms in all the other F, $\textnormal{m}_\textnormal{F}$ states. Excluding the forward scattering and detecting only scattered atoms with velocity sensitive Raman transitions, we measure Ramsey fringes with a phase shift that is the difference of the clock states' s-wave quantum scattering phase shifts for scattering off of the target atoms [1,2]. We measure the magnetic field dependence of this differential phase shift and our low spread in collision energy yields phase variations of order $\pm \pi$/2 through a series of narrow Feshbach resonances. These measurements give a precise picture of cesium interactions, which in turn is expected to reduce the current uncertainty of the ultracold collision frequency shift below 100nK for laser-cooled space clocks and could also lead to stringent limits on the time variation of fundamental constants [3].\\[4pt] [1] R. A. Hart et al. Nature {\bf 446}, 892 (2007).\\[0pt] [2] S. D. Gensemer et al. Phys. Rev. Lett. {\bf 109}, 263201 (2012).\\[0pt] [3] C. Chin et al., Phys. Rev. Lett. {\bf 96}, 230801 (2006) [Preview Abstract] |
Thursday, June 11, 2015 9:48AM - 10:00AM |
M8.00010: Magnetic field enabled Lamb-Dicke spectroscopy of the \textsuperscript{1}S$_0$-\textsuperscript{3}P$_0$ transition in \textsuperscript{24}Mg Ernst M. Rasel, Andre Kulosa, Dominika Fim, Klaus Zipfel, Steffen Sauer, Wolfgang Ertmer We succeeded in optically exciting the electronic state \textsuperscript{3}P$_0$ in \textsuperscript{24}Mg by quenching its lifetime with the help of a magnetic field. The atoms were laser cooled and trapped in an optical lattice tuned to the magic wavelength, where the ac Stark shift of the transition vanishes. In this way we determined the transition frequency, the magic wavelength and the quadratic magnetic Zeeman shift and can compare the observed values with the predictions based on theoretical models and previous experiments. We also will discuss the performance of a clock operated with bosonic magnesium. [Preview Abstract] |
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