Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session C7: Atomic ClocksPress Undergraduate
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Chair: David Phillips, Harvard-Smithsonian Center for Astrophysics Room: 553AB |
Tuesday, May 24, 2016 2:00PM - 2:12PM |
C7.00001: Thorium-229 solid-state nuclear clock prospects in MgF$_2$ and LiSAF Edmund Meyer, Beau Barker, Lee Collins The ${}^{229}$Th isomer is thought to be a good candidate for a nuclear clock based on its relatively low-energy isomer excitation of $\approx\,7.8$\,eV. We report on the study of Th atoms embedded in two crystals, MgF$_2$ and LiSAF (LiSrAlF$_6$). For MgF$_2$ we perform an oxidation study to find the preferred ionization state of the Th atom in the crystal; Th$^{n+}$, where $n=2-4$. We find that the preferred state is $n=4$ which requires two interstitial Fluorine atoms to charge compensate. Using the results of MgF$_2$ we then search within LiSAF for suitable dopant sites (the Sr, Al, or Li can all serve). Employing a standard density functional package using a plane-wave basis and psuedopotentials, we optimize a doped cell of increasing particle number sizes and use this to estimate the dilute doped-limit band-gap of LiSAF. Placement of the dopant on the Sr and Al sites with accompanying double and single F interstitial atom placements is also studied to determine the ground state, and comparisons are made with previous calculations\,[1]. In both crystal ground states, we find that the band gap is large enough for the observation of the ${}^{229}$Th nuclear isomer transition; $> 9$\,eV. \\ \, [1] R. A. Jackson et al., J. Phys.: Condens. Matter 21, 325401 (2009). [Preview Abstract] |
Tuesday, May 24, 2016 2:12PM - 2:24PM |
C7.00002: The NIST $^{27}$Al$^+$ quantum-logic clock David Leibrandt, Samuel Brewer, Jwo-Sy Chen, David Hume, Aaron Hankin, Yao Huang, Chin-Wen Chou, Till Rosenband, David Wineland Optical atomic clocks based on quantum-logic spectroscopy of the $^1$S$_0$~ $\leftrightarrow$~$^3$P$_0$ transition in $^{27}$Al$^+$ have reached a systematic fractional frequency uncertainty of $8.0\times10^{-18}$, enabling table-top tests of fundamental physics as well as measurements of gravitational potential differences. Currently, the largest limitations to the accuracy are second order time dilation shifts due to the driven motion (i.e., micromotion) and thermal motion of the trapped ions. In order to suppress these shifts, we have designed and built new ion traps based on gold-plated, laser-machined diamond wafers with differential RF drive, and we have operated one of our clocks with the ions laser cooled to near the six mode motional ground state. We present a characterization of the time dilation shifts in the new traps with uncertainties near $1\times10^{-18}$. Furthermore, we describe a new protocol for clock comparison measurements based on synchronous probing of the two clocks using phase-locked local oscillators, which allows for probe times longer than the laser coherence time and avoids the Dick effect. [Preview Abstract] |
Tuesday, May 24, 2016 2:24PM - 2:36PM |
C7.00003: Pulse defect immune Ramsey spectroscopy Christian Sanner, Nils Huntemann, Sergey Kuznetsov, Burghard Lipphardt, Christian Tamm, Ekkehard Peik We show that a balanced version of Ramsey's method of separated oscillatory fields is well suited for measuring unperturbed transition frequencies of atomic reference transitions that suffer from significant clock shifts in the presence of the oscillatory drive fields. Using the example of the strongly light shift affected Yb171$+$ octupole transition [1] we experimentally demonstrate the feasibility of this concept and show that no systematic clock shifts are incurred for arbitrarily detuned drive pulses. Unlike composite pulse approaches as proposed in [2] balanced Ramsey spectroscopy can provide universal immunity to a variety of pulse aberrations and drive pulse induced shifts including phase chirps and pulse-synchronous intensity variations. In this context we also devise an experimental method addressing issues related to motional heating of the confined ion. Furthermore we report on the status of an Yb$+$ experiment searching for signatures of spatial anisotropy. [1] PRL 108, 090801 (2012), [2] PRA 82, 011804 (2010) [Preview Abstract] |
Tuesday, May 24, 2016 2:36PM - 2:48PM |
C7.00004: Energy shift due to anisotropic black body radiation Sergey Porsev, Victor Flambaum, Marianna Safronova In many applications a source of the black-body radiation (BBR) can be highly anisotropic. This leads to the black-body radiation shift that depends on tensor polarizability and on the projection of the total angular momentum of ions and atoms in a trap. We derived formula for the anisotropic BBR shift and performed numerical calculations of this effect for Ca$^+$ and Yb$^+$ transitions of experimental interest. These ions are used for a design of high-precision atomic clocks, fundamental physics tests such as search for the Lorentz invariance violation and space-time variation of the fundamental constants, and quantum information. Anisotropic BBR shift may be one of the major systematic effects in these experiments. [Preview Abstract] |
Tuesday, May 24, 2016 2:48PM - 3:00PM |
C7.00005: Magic Wavelength for the Hydrogen 1S-2S Transition Akio Kawasaki The state of the art precision measurement of the transition frequencies of neutral atoms is performed with atoms trapped by the magic wavelength optical lattice that cancels the ac Stark shift of the transitions. Trapping with magic wavelength lattice is also expected to improve the precision of the hydrogen 1S-2S transition frequency, which so far has been measured only with the atomic beam. In this talk, I discuss the magic wavelength for the hydrogen 1S-2S transition, and the possibility of implementing the optical lattice trapping for hydrogen. Optical trapping of hydrogen also opens the way to perform magnetic field free spectroscopy of antihydrogen for the test of CPT theorem. [Preview Abstract] |
Tuesday, May 24, 2016 3:00PM - 3:12PM |
C7.00006: Extracting transition rates from zero-polarizability spectroscopy Zuhrianda Zuhrianda, Marianna S Safronova, Ulyana I Safronova, Charles W Clark Accurate knowledge of atomic properties has been critical for the design and interpretation of experiments, quantifying and reducing uncertainties and decoherence, and development of concepts for next-generation experiments and precision measurement techniques. We predict a sequence of magic-zero wavelengths for which ac Stark shift vanishes for the Sr excited $5s5p ^3P_0$ state, and provide a general roadmap for extracting transition matrix elements using precise frequency measurements. We demonstrate that such measurements can serve as a best global benchmark of the spectroscopic accuracy that is required for the development of high-precision predictive methods. These magic-zero wavelengths are also needed for state-selective atom manipulation for implementation of quantum logic operations. We also identify five magic wavelengths of the $5s^2\ ^1S_0 - 5s5p\ ^3P_0$ Sr clock transition between 350 nm and 500 nm which can also serve as precision benchmarks. [Preview Abstract] |
Tuesday, May 24, 2016 3:12PM - 3:24PM |
C7.00007: Measurement of an atomic quadrupole moment using dynamic decoupling Nitzan Akerman, Ravid Shaniv, Roee Ozeri Some of the best clocks today are ion-based optical clocks. These clocks are referenced to a narrow optical transition in a trapped ion. An example for such a narrow transition is the electric quadrupole $E2$ transition between states with identical parity. An important systematic shift of such a transition is the quadrupole shift resulting from the electric field gradient inherent to the ion trap. We present a new dynamic decoupling method that rejects magnetic field noise while measuring the small quadrupole shift of the optical clock transition. Using our sequence we measured the quadrupole moment of the $4D_{\frac{5}{2}}$ level in a trapped $^{88}Sr^{+}$ ion to be $2.973^{+0.026}_{-0.033}\, ea_{0}^{2}$, where $e$ is the electron charge and $a_{0}$ is the Bohr radius. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in $^{88}Sr^{+}$ based optical atomic clocks and verifies complicated many-body quantum calculations. (Ref: arXiv:1511.07277 2015) [Preview Abstract] |
Tuesday, May 24, 2016 3:24PM - 3:36PM |
C7.00008: Solar radial velocity variations and the search for Venus enabled by a laser frequency comb David F. Phillips, Xavier Dumusque, Chih-Hao Li, Alexander Glenday, Dimitar Sasselov, Andrew Szentgyorgyi, Ronald L. Walsworth We have recently demonstrated 50 cm/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple, compact 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 have been operating the solar telescope to detect the RV signal of the Sun as a star for the past year both to study RV jitter associated with stellar (solar) fluctuations and to demonstrate sensitivity of these instruments to detect terrestrial exoplanets. In this talk I will present results from calibrating the HARPS-N exoplanet searcher spectrograph, solar RV stability, and the current status of our search for the signature of Venus. [Preview Abstract] |
Tuesday, May 24, 2016 3:36PM - 3:48PM |
C7.00009: Searching for Dark Matter with Atomic Clocks and Laser Interferometry Yevgeny Stadnik, Victor Flambaum We propose new schemes for the direct detection of low-mass bosonic dark matter, which forms a coherently oscillating classical field and resides in the observed galactic dark matter haloes, using atomic clock, atomic spectroscopy and laser interferometry measurements in the laboratory. We have recently shown that such dark matter can produce both a `slow' cosmological evolution and oscillating variations in the fundamental constants [Stadnik and Flambaum, PRL 115, 201301 (2015); PRL 113, 151301 (2014)]. Using recent atomic dysprosium spectroscopy measurements in [Van Tilburg et al., PRL 115, 011802 (2015)], we have derived limits on the quadratic interactions of scalar dark matter with ordinary matter that improve on existing constraints by up to 15 orders of magnitude [Stadnik and Flambaum, PRL 115, 201301 (2015)]. We have also proposed the use of laser and maser interferometry as novel high-precision platforms to search for dark matter, with effects due to the variation of the electromagnetic fine-structure constant on alterations in the accumulated phase enhanced by up to 14 orders of magnitude [Stadnik and Flambaum, PRL 114, 161301 (2015); arXiv:1511.00447]. Other possibilities include the use of highly-charged ions, molecules and nuclear clocks. [Preview Abstract] |
Tuesday, May 24, 2016 3:48PM - 4:00PM |
C7.00010: The search for axion-like dark matter using magnetic resonance Alexander Sushkov The nature of dark matter is one of the most important open problems in modern physics, and it is necessary to develop techniques to search for a wide class of dark-matter candidates. Axions, originally introduced to resolve the strong CP problem in quantum chromodynamics (QCD), and axion-like particles (ALPs) are strongly motivated dark matter candidates. Nuclear spins interacting with axion-like background dark matter experience an energy shift, oscillating at the frequency equal to the axion Compton frequency. The Cosmic Axion Spin Precession Experiments (CASPEr) use precision magnetometry and nuclear magnetic resonance techniques to search for the effects of this interaction. The experimental signature is precession of the nuclear spins under the condition of magnetic resonance: when the bias magnetic field is tuned such that the nuclear spin sublevel splitting is equal to the axion Compton frequency. These experiments have the potential to detect axion-like dark matter in a wide mass range ($10^{-12}$ eV to $10^{-6}$ eV, scanned by changing the bias magnetic field from approximately 1 gauss to 20 tesla) and with coupling strengths many orders of magnitude beyond the current astrophysical and laboratory limits, and all the way down to those corresponding to the QCD axion. [Preview Abstract] |
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