Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session P02: Advances in Optical Atomic Clocks |
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Sponsoring Units: GPMFC Chair: Chin-wen Chou, NIST Room: Wisconsin Center 101AB |
Thursday, May 30, 2019 10:30AM - 11:00AM |
P02.00001: Three optical frequency ratios and a clock network below the $10^{-17}$ level Invited Speaker: Dhruv Kedar Optical atomic clocks based on narrow-linewidth optical transitions have realized unprecedented levels of stability, precision, and accuracy. At this level, evaluation by microwave standards becomes unfeasible as the standards themselves are limited to an accuracy worse than their optical counterparts. Direct evaluation of optical frequency ratios circumvents this problem and is a precursor for the redefinition of the SI second based on optical standards, as well as searches for fundamental physics. Here, we will describe the results of a three-way interspecies atomic clock comparison performed at JILA and NIST, involving the 87Sr and 171Yb optical lattice clocks, and the 27Al$^+$ ion clock. All clocks report fractional inaccuracies at the $10^{-18}$ level. Two of the atomic ratios are simultaneously measured with an underground 1.5km long telecom fiber and a free-space link based on optical two-way time transfer and agree at the $10^{-18}$ level. Together, these evaluations demonstrate a robust optical clock network with the most accurate set of optical frequency ratios measured\footnote{Measurements performed by the Boulder Area Clock Network collaboration}. [Preview Abstract] |
Thursday, May 30, 2019 11:00AM - 11:30AM |
P02.00002: Frequency comparisons of individual Yb+ ions Invited Speaker: Ekkehard Peik In the development of single-ion optical frequency standards with $^{171}$Yb$^+$ we use two reference transitions (E2 and E3) in the same ion for the diagnosis and correction of systematic shifts, and comparisons between ions in different traps to test their agreement. We have observed agreement of two frequency standards on the E3 transition to within their combined systematic uncertainty of $3.6\times 10^{-18}$ and have obtained more stringent limits on violations of Lorentz symmetry. Using a clock laser with mHz-linewidth, it will be possible to interrogate the E3 transition with Ramsey times of many seconds. We plan to use sympathetic cooling of Yb$^+$ with Sr$^+$ to reduce the effects of ion heating. Together with a consortium (www.opticlock.de) with industrial partners we are building a demonstrator $^{171}$Yb$^+$ E2 frequency standard for autonomous operation outside of specialized metrology laboratories. [Preview Abstract] |
Thursday, May 30, 2019 11:30AM - 11:42AM |
P02.00003: Updates on Yb optical lattice clocks at NIST Youssef Hassan, William McGrew, Xiaogang Zhang, Robert Fasano, Daniele Nicolodi, Kyle Beloy, Wesley Brand, Stephan Schaffer, Roger Brown, Jian Yao, Jeffrey Sherman, Thomas Parker, Holly Leopardi, Tara Fortier, Andrew Ludlow Optical atomic clocks have enabled the next generation of precision measurement surpassing the performance of the current cesium standard. The Yb optical lattice clock is one strong candidate for redefining the SI second, with recent progress in the systematic uncertainty, measurement instability, and reproducibility at or below the $10^{-18}$ fractional level. Here, we report an improved absolute frequency measurement of the Yb clock transition frequency at an inaccuracy limited by the current definition of the SI second. These measurements are analyzed to yield an improved constraint on possible variation in the electron-to-proton mass ratio. We also highlight high-precision optical-frequency-ratio measurements using optical clocks at NIST based on Yb, Sr, and $\mathrm{Al^{+}}$. Finally, we describe recent efforts to improve the clock transition detection scheme and blackbody radiation shift uncertainty in the Yb lattice clock. [Preview Abstract] |
Thursday, May 30, 2019 11:42AM - 11:54AM |
P02.00004: Correlation spectroscopy between two $^{27}$Al$^+$ clocks May E. Kim, E. R. Clements, A. M. Hankin, S. M. Brewer, J.-S. Chen, C. W. Chou, D. J. Wineland, D. B. Hume, D. R. Leibrandt A comparison between highly accurate clocks, which is necessary to evaluate and verify their accuracy, requires commensurate measurement precision. While the atomic systems used as clocks have long coherence times, noise from the local oscillator often limits the measurement stability. One way to overcome this limitation is by performing correlation spectroscopy, in which a Ramsey pulse sequence derived from the same probe laser is applied to both clocks synchronously. The coherent differential frequency measurements between two atomic systems permit interrogation times beyond the laser coherence time. We report on the demonstration of correlation spectroscopy between two independent optical atomic clocks in separate systems. By removing the limitation set by the coherence time of the local oscillator, we extend the interrogation time of the two single $^{27}$Al$^+$ ion quantum-logic clocks from 150~ms to several seconds. The corresponding reduction in quantum projection noise limit results in a frequency comparison instability significantly lower than is possible for incoherent comparisons using the same local oscillator. [Preview Abstract] |
Thursday, May 30, 2019 11:54AM - 12:06PM |
P02.00005: An $^{27}$Al$^{+}$ quantum-logic clock with systematic uncertainty below $10^{-18}$ Samuel Brewer, Jwo-Sy Chen, Aaron Hankin, Ethan Clements, Chin-wen Chou, David Wineland, David Hume, David Leibrandt We describe an optical atomic clock based on quantum-logic spectroscopy of the $^1$S$_0$ $\leftrightarrow$ $^3$P$_0$ transition in $^{27}$Al$^{+}$ with a systematic uncertainty of $9.0 \times 10^{-19}$ and a frequency stability of $1.2 \times~10^{-15}/\sqrt{\tau}$. A $^{25}$Mg$^{+}$ ion is simultaneously trapped with the $^{27}$Al$^{+}$ ion and used for sympathetic cooling and state readout during clock operation. Improvements in a new trap have led to reduced secular motion heating, compared to previous $^{27}$Al$^{+}$ clocks, enabling clock operation with ion motion near the three-dimensional ground state. Operating the clock with a lower trap drive frequency has reduced excess micromotion, compared to previous $^{27}$Al$^{+}$ clocks, leading to a reduced time-dilation shift uncertainty. Other systematic uncertainties including those due to blackbody radiation and the second-order Zeeman effect have also been reduced. \footnote{Work supported by NIST, DARPA, and ONR. S.M.B. was supported by ARO through MURI grant W911NF-11-1-0400.} [Preview Abstract] |
Thursday, May 30, 2019 12:06PM - 12:18PM |
P02.00006: Progress on multi-ion optical clock with $^{176}\mathrm{Lu}^+$ Rattakorn Kaewuam, Ting Rei Tan, Kyle Arnold, Murray Barrett The stability of the current generation of ion-based optical clocks is limited due to the restriction to single-ion operation. Multi-ion operation is complicated by inhomogenous magnetic fields, micromotion-related shifts induced by the trapping radio-frequency field, and electric quadrupole shifts arising from the Coulomb fields of neighboring ions. The three clock transitions in $^{176}\mathrm{Lu}^+$ have favorable properties for multi-ion operation including, low sensitivity to magnetic fields, low differential static scalar polarizability, and the quadrupole shifts can be suppressed by appropriate orientation of the applied magnetic field. Here, we report progress on establishing clock operation on a small linear Coulomb crystal of lutetium ions. [Preview Abstract] |
Thursday, May 30, 2019 12:18PM - 12:30PM |
P02.00007: $^{87}$Sr Optical Lattice Clock Comparison with 6$\times 10^{-19}$ Precision in 1 Hour Tobias Bothwell, Dhruv Kedar, Eric Oelker, Colin Kennedy, John Robinson, Ross Hutson, Lindsay Sonderhouse, Akihisa Goban, William Milner, Christian Sanner, Jun Ye Utilizing a next generation ultrastable laser based on a cryogenic silicon cavity we perform an extensive comparison between JILA’s 1D and 3D strontium clocks, achieving record independent clock stability of 4.8$\times 10^{-17}$ at 1 s. Through synchronous measurement we determine record clock stability of 3.5$\times 10^{-17}$ at 1 s and average to a precision of 6$\times 10^{-19}$ in 1 hour of measurement. This state-of-the-art clock precision enables measurements for wide-ranging applications, from searches for dark matter to relativistic geodesy. Additionally, the combined accuracy of our fully evaluated 1D $^{87}$Sr clock with the long-term stability of the silicon cavity paves a potential path to the realization of an all optical timescale, which promises to outperform current microwave timescales. [Preview Abstract] |
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