Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session S4: Precision Measurements and Clocks |
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Sponsoring Units: GPMFC Chair: Kristan Corwin, Kansas State University Room: Regency Ballroom |
Friday, May 28, 2010 2:00PM - 2:12PM |
S4.00001: Precision measurements of atomic g factor ratios using a dual species MOT I. Chan, R. Berthiaume, B. Barrett, C. Mok, A. Carew, A. Kumarakrishnan We describe progress toward a precision measurement of atomic $g$ factor ratios in a dual species MOT using a coherent transient technique referred to as magnetic grating free induction decay (MGFID)\footnote{I. Chan \textit{et al}., Phys. Rev. A \textbf{78}, 033418 (2008).}. In the experiment, a sample of laser cooled atoms is excited using two laser pulses with orthogonal polarizations. In a constant magnetic field, the MGFID signal exhibits oscillations at the Larmor frequency. Using a scheme in which both $^{85}$Rb and $^{87}$Rb atoms are simultaneously loaded from the background vapor into a dual isotope magneto optical trap (MOT), we measure the ratio of atomic $g$ factors between the $^{85}$Rb $F = 3$ and $^{87}$Rb $F = 2$ ground states by extracting the Larmor frequency from the MGFID signal. [Preview Abstract] |
Friday, May 28, 2010 2:12PM - 2:24PM |
S4.00002: A dual-isotope rubidium magnetometer for probing anomalous spin-dependent interactions of the proton Ian Lacey, L.R. Jacome, Lok Fai Chan, Rodrigo Peregrina, Delyana Delcheva, Derek Kimball We report progress in our development of a dual-isotope rubidium magnetometer to be used to search for anomalous spin-dependent interactions of the proton, in particular a long-range coupling between proton spins and the mass of the Earth. The valence electron dominates magnetic interactions and serves as a precise co-magnetometer for the nuclei in a simultaneous measurement of Rb-85 and Rb-87 spin precession frequencies, enabling accurate subtraction of magnetic perturbations. Both Rb nuclei have valence protons, but in Rb-87 the proton spin is parallel to the nuclear spin and magnetic moment while for Rb-85 the proton spin is anti-parallel to the nuclear spin and magnetic moment. Thus anomalous interactions of the proton spin produce a differential shift between the Rb spin-precession frequencies, whereas many sources of systematic error produce common-mode shifts of the spin-precession frequencies which can be controlled through auxiliary measurements. The majority of recent searches for similar effects limit anomalous couplings of either the neutron or electron spin, so the proposed experiments search a parameter space to some degree, depending on the theoretical model, orthogonal to that constrained by previous experiments. [Preview Abstract] |
Friday, May 28, 2010 2:24PM - 2:36PM |
S4.00003: Sensitivity of microwave spectra of molecules to variation of electron-to-proton mass ratio Mikhail Kozlov, Alexander Lapinov, Sergey Levshakov We estimate sensitivity coefficients $Q_\mu$ to variation of the electron-to-proton mass ratio $\mu=m_e/m_p$ for microwave transitions in partly deuterated ammonia and for $\Lambda$-doublet transitions in light diatomics. For NH$_2$D and ND$_2$H molecules the rotational and inversion degrees of freedom are mixed. Because of that, the coefficients $Q_\mu$ strongly depend on the quantum numbers of the transition. The same applies to the $\Lambda$-doublet transitions in such molecules as CH and OH, where electron spin decouples from the molecular axis as rotational quantum number $J$ increases. Microwave lines with large coefficients $Q_\mu$ can be used for astrophysical and laboratory search for possible variation of the constant $\mu$. [Preview Abstract] |
Friday, May 28, 2010 2:36PM - 2:48PM |
S4.00004: Universal Corrections to Gyromagnetic Ratios of Bound Particles with Arbitrary Spins Timothy Martin, Michael Eides The leading relativistic and recoil corrections for bound state anomalous magnetic moment are calculated. It is demonstrated that these corrections are universal for any spin and depend only on the free particle gyromagnetic ratio. To prove this universality we develop NRQED for charged particles with an arbitrary spin. We also confirm that the coefficients in the Bargmann-Michael-Telegdi equation for spin motion in an external field depend only on the gyromagnetic ratio, and are independent of the magnitude of spin. [Preview Abstract] |
Friday, May 28, 2010 2:48PM - 3:00PM |
S4.00005: Progress towards a precision measurement of atomic recoil frequency using an echo interferometer B. Barrett, A. Carew, S. Beattie, I. Chan, C. Mok, R. Berthiaume, A. Kumarakrishnan We discuss progress toward a precision measurement of the atomic recoil frequency in $^{85}$Rb using an echo-type atom interferometer and a new technique [Phys. Rev. A \textbf{79}, 021605(R) (2009)]. At time $t = 0$, a standing wave pulse (swp) creates a superposition of momentum states. The coherence of these $p$-states decays quickly due to the velocity distribution of the laser cooled sample. At $t = T$, a 2nd swp diffracts the $p$-states again and a density grating associated with the interference of $p$-states differing by multiples of the 2-photon recoil momentum ($n \hbar q = 2 n \hbar k$) is formed in the vicinity of $t = 2T$. A traveling wave readout pulse Bragg scatters light only from the grating with spatial periodicity $\lambda/2$ (associated with interfering $p$-states differing by $\hbar q$). The backscatterd light is detected as the signal. A 3rd swp (applied at $t = 2T - \delta T$) converts the difference between interfering $p$-states from $n\hbar q$ to $\hbar q$. All interfering orders of $p$-states contribute to the signal at $t = 2T$. As a function of $\delta T$, the signal shape exhibits narrow fringes that revive periodically at the 2-photon recoil period, $\pi/\omega_q$. We have achieved a single measurement precision of $\sim 500$ ppb on a timescale of $2T \sim 48$ ms. Further improvements are anticipated by extending the timescale and narrowing the fringe width. This work is supported by CFI, OIT, NSERC, OCE, and York University. [Preview Abstract] |
Friday, May 28, 2010 3:00PM - 3:12PM |
S4.00006: Relativity and Al$^+$ Optical Clocks Chin-wen Chou, David B. Hume, David J. Wineland, Till Rosenband We have constructed an optical clock based on quantum logic spectroscopy of an Al+ ion that has a fractional frequency inaccuracy of $8.6\times10^{-18}$. The frequency of the $^1$S$_0$$\leftrightarrow$$^3$P$_0$ clock transition is compared to that of a previously constructed Al$^+$ optical clock with a statistical measurement uncertainty of $7.0\times10^{-18}$. The two clocks exhibit a relative stability of $2.8\times10^{-15}\tau^{-1/2}$, and a fractional frequency difference of $-1.8\times10^{-17}$, consistent with the accuracy limit of the older clock. By comparing the frequencies of the clocks, we have observed relativistic effects, such as time dilation due to velocities less than 10 m/s and the gravitational red shift from a 0.33~m height change of one of the clocks. [Preview Abstract] |
Friday, May 28, 2010 3:12PM - 3:24PM |
S4.00007: Towards a lattice based neutral magnesium optical frequency standard Hrishikesh Kelkar, Matthias Riedmann, Temmo Wuebbena, Andre Kulosa, Jan Friebe, Andre Pape, Sana Amairi, Sina Malobabic, Klaus Zipfel, Steffen Ruehmann, Ernst -Maria Rasel, Wolfgang Ertmer Magnesium is a promising candidate for a high performance neutral atom optical frequency standard. It offers a low sensitivity to frequency shifts of the $^{1}$S$_{0}-^{3}$P$_{0}$ clock transition by room temperature blackbody radiation and has several isotopes of suitable abundance (two bosonic, one fermionic) to realize an optical clock. We report on recent progress towards creating a lattice clock of magnesium. $^{24}$Mg atoms are pre-cooled in two stages. The singlet Magneto Optical Trap (MOT) captures and cools atoms from an atomic beam which are then loaded into a triplet MOT. The triplet MOT has a decay channel to the dark $^{3}$P$_{0}$ state which is used to load atoms into a 1064 nm dipole trap. The cooling stages are on simultaneously and atoms are continuously loaded in the dipole trap. We capture upto 9 10$^{4}$ atoms at a temperature below 100 $\mu $K. We are exploring different avenues for further cooling which will enable reaching the Lamb-Dicke regime in a magic wavelength lattice. [Preview Abstract] |
Friday, May 28, 2010 3:24PM - 3:36PM |
S4.00008: Suppression of collisional shifts in an optical lattice clock by trapping atoms in a 2D lattice Matthew Swallows, Michael Bishof, Yige Lin, Michael Martin, Sebastian Blatt, Ana-Maria Rey, Jun Ye Optical atomic clocks based on ensembles of neutral alkaline earth atoms trapped in a magic wavelength optical lattice are promising candidates for the future generation of frequency standards\footnote{A. D. Ludlow \textit{et al.,} Science, \textbf{319}(5871) pp. 1805-1808, 2008.}. One advantage of neutral atom clocks is the simultaneous interrogation of a large number of atoms, which can in principle allow them to surpass the stability achievable with clocks based on single ions. However, several obstacles must be overcome before this advantage can be realized. One of these is atomic density-dependent collisional shifts of the clock transition, which can occur even if the clock is based on an ensemble of ultracold fermions\footnote{G. K. Campbell \textit{et al.,} Science, \textbf{324}(5925) pp. 360-363, 2009.}. We will report on recent efforts to eliminate collisional shifts affecting the JILA $^{87}$Sr optical lattice clock by trapping atoms in a two-dimensional optical lattice. Collisional shifts will be suppressed by a novel mechanism that should operate even if each one-dimensional tube-like lattice site contains $N \gg 1$ atoms. [Preview Abstract] |
Friday, May 28, 2010 3:36PM - 3:48PM |
S4.00009: Experimental observation of magic-wavelength behavior of a microwave transition in optical lattice-trapped rubidium Nathan Lundblad, Malte Schlosser, Trey Porto We demonstrate the cancellation of the differential ac Stark shift of the microwave hyperfine clock transition in trapped $^{87}$Rb atoms. Recent progress in metrology exploits so-called ``magic wavelengths," whereby an atomic ensemble can be trapped with laser light whose wavelength is chosen so that both levels of an optical atomic transition experience identical ac Stark shifts. Similar magic-wavelength techniques are not possible for the microwave hyperfine transitions in the alkalis, due to their simple electronic structure. We show, however, that ac Stark shift cancellation is indeed achievable for certain values of wavelength, polarization, and magnetic field. The cancellation comes at the expense of a small magnetic-field sensitivity. The technique demonstrated here has implications for experiments involving the precise control of optically-trapped neutral atoms. [Preview Abstract] |
Friday, May 28, 2010 3:48PM - 4:00PM |
S4.00010: Scalar and vector differential light shift measurements in optical lattice-trapped $^{87}$Rb Radu Chicireanu, Karl Nelson, Steven Olmschenk, Trey Porto The existence of `magic wavelengths' for hyperfine transitions in alkali atoms is of great interest for their applications in quantum information and frequency metrology. Magic wavelength predictions for Rb and Cs have met with some controversy, and it is likely that they do not exist in `traditional' optical lattices. In a state-dependent lattice though, the scalar and vector differential light shifts can have opposite signs, leading to a prospected significant reduction in the sensitivity of the transition frequency to fluctuations in the trapping light field. We investigate this effect, and present preliminary results of a precision measurement of light shifts in lattice-trapped $^{87}$Rb, focusing on the differential light shift between the ground-state hyperfine levels F=1,2. [Preview Abstract] |
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