Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session J5: Matter Wave Interferometry |
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Chair: Alex Cronin, University of Arizona Room: Nittany Lion Inn Boardroom I |
Thursday, May 29, 2008 11:00AM - 11:12AM |
J5.00001: Influence of Spontaneous Emission on a Single-State Atom Interferometer S. Beattie, B. Barrett, M. Weel, I. Chan, C. Mok, S.B. Cahn, A. Kumarakrishnan We have studied the effects of spontaneous emission (SE) on a single-state time domain atom interferometer (AI) that uses trapped Rb atoms. The AI uses two standing waves pulses separated by time $T$ to produce an echo signal at time $2T$ due to interference between momentum states. We find that SE influences both the shape of the echo signal and its periodic time dependent amplitude in a manner consistent with theoretical predictions. The results show that the time dependent signal from the AI is related to the effective radiative decay rate of the excited state. We also present results that test theoretical predictions for several properties of the echo formation such as the variation in momentum transfer due to the change in the angle between the traveling wave components of the excitation pulses, strength of the atom-field interaction, and the effect of spatial profile of the excitation beams. These studies are important for realizing precision measurements of the atomic fine structure constant and gravity using this interferometer. The details of this work are described in PRA \textbf{77}, 013610 (2008). [Preview Abstract] |
Thursday, May 29, 2008 11:12AM - 11:24AM |
J5.00002: Decoherence Due to Light Scattering and Collisions on a Single State Atom Interferometer S. Beattie, I. Chan, A. Kumarakrishnan We have measured the effects of light scattering and collisions on the signal from a single state atom interferometer that uses laser cooled $^{85}Rb$. Two standing wave pulses separated by time $T$ are used to diffract and rephase momentum states (corresponding to a single internal state) resulting in the formation of a density grating in the vicinity of $t=2T$. The grating is detected by measuring an echo signal that represents the amplitude of light backscattered by a traveling wave. Decoherence due to light scattering and collisions reduces the timescale over which matter wave interference can be detected. To study the effects of light scattering, we apply both traveling wave and standing wave pulses at a variable time $\delta t$ before grating formation at $t=2T$ and measure the echo amplitude. In both cases, the matter wave interference shows a periodic dependence on $\delta t$ that is consistent with theoretical predictions based on the Fourier transforms of the momentum distributions associated with the decohering pulses. We also present studies of dcoherence due to cw standing wave light and collisions by measuring the echo amplitude as a function of $T$. [Preview Abstract] |
Thursday, May 29, 2008 11:24AM - 11:36AM |
J5.00003: Monte Carlo Wavefunction Simulation of a Matter Wave Interferometer Brynle Barrett, Carson Mok, Scott Beattie, A. Kumarakrishnan We present Monte Carlo wavefunction (MCWF) simulations to understand a single state atom interferometer used to measure the atomic recoil frequency with laser cooled atoms. In the experiment, a standing wave laser is pulsed on at $t = 0$ which creates a superposition of momentum states. At $t = T$, a second standing wave pulse diffracts the momentum states again so that a density grating is formed in the vicinity of $t = 2T$. This grating is associated with the interference of momentum states separated by $2\hbar k$. A traveling wave readout pulse is applied to the sample at this time and the backscattered light from the grating is detected as the signal. The MCWF approach is used to model several aspects of the experiment, such as the dependence of the signal on the laser intensity profile, pulse length and spontaneous emission. The MCWF method is a well-known approach for solving dissipation problems in quantum optics. The method is equivalent to a master equation approach, but the random nature of quantum jumps is simulated more directly using a Monte Carlo treatment. [Preview Abstract] |
Thursday, May 29, 2008 11:36AM - 11:48AM |
J5.00004: Measuring Relative Atom Number Fluctuations in Coherently Split Quantum Degenerate Gases Marcius H.T. Extavour, Jason McKeever, Lindsay J. LeBlanc, Dylan Jervis, Alan Stummer, Thorsten Schumm, Joseph H. Thywissen We report on direct measurements of atom number fluctuations in a double-well Bose Einstein condensate (BEC) system. A single BEC is dynamically and coherently split into two halves -- left (L) and right (R). This is accomplished by deforming a single 3-dimensional harmonic magnetic trap into a double-well trap by combining static and time-varying radio-frequency magnetic fields on an atom chip. Fluctuations in the relative atom number Nr = NR - NL in repeated trials are evaluated against the shot-noise preduction of binomial statistics. We determine the atom number statistics of the splitting process by directly measuring the atom numbers in the left and right wells after splitting, and the fluctuations in the relative atom number in successive repetitions of the experiment using time-of-flight absorption imaging. We will discuss possible extensions of this method to measurements of splitting statistics using a degenerate Fermi gas. [Preview Abstract] |
Thursday, May 29, 2008 11:48AM - 12:00PM |
J5.00005: Study the Effect of an Atom-Optics Kicked Rotor on a de Broglie Wave Atom Interferometer Alexey Tonyushkin, Saijun Wu, Mara Prentiss We experimentally study the impact of an atomic kicked rotor on the ``echo'' signal output of a de~Broglie wave interferometer. We relate the kicked rotor induced decoherence in the interferometer signal to the perturbation induced decay of the quantum fidelity amplitude. There have been several experimental and theoretical studies of fidelity decay for a spin-echo perturbed by a kicked rotor. In contrast with such internal state experiments, in our implementation delta- function-like optical standing wave pulses act on external states creating an instantaneous phase-space displacement perturbation\footnote{C.~Petitjean, {\em et al.}, Phys. Rev. Lett. {\bf 98}, 164101 (2007)}. Depending on the initial conditions we observed two different regimes: perfect coherence preservation independent on the number and strength of pulses applied, and a fidelity decay freeze at a finite value after just a small number of kicks at quantum resonance conditions of a quantum kicked rotor\footnote{S. Wu, A. Tonyushkin, and M. G. Prentiss, arXiv:0801.0475v1}. We also discuss the transition from a classical (vanishing kicking period case) to a quantum delta kicked rotor model. The observed effects may have applications in precision measurements. [Preview Abstract] |
Thursday, May 29, 2008 12:00PM - 12:12PM |
J5.00006: Selective Manipulation of Degenerate Interferometer Loops by an Atom-Optics Kicked Rotor Alexey Tonyushkin, Mara Prentiss We experimentally demonstrate that an atom-optics kicked rotor can lift the degeneracy in a four-pulse de~Broglie wave atom interferometer. The interferometer output is dominated by two degenerate spatial loops: the non-reciprocal ``trapezoid'' loop and the reciprocal ``figure-8'' loop. By applying the kicked rotor sequence at a particular time we can greatly reduce the contribution of the trapezoid loop to the interferometer signal while preserving the contribution due to the ``figure-8'' loop. When the degeneracy is present, the interferometer is sensitive to both rotation and linear acceleration. When the degeneracy is lifted the interferometer is insensitive to linear acceleration, but still sensitive to rotation. The suppression of non-reciprocal loops in an atom interferometer is valuable for rotation sensing [1]. \newline \newline [1] T. L. Gustavson {\em et al.}, Phys. Rev. Lett. {\bf 78}, 2046 (1997); S.~Wu {\em et al.}, Phys. Rev. Lett. {\bf 99}, 173201 (2007). [Preview Abstract] |
Thursday, May 29, 2008 12:12PM - 12:24PM |
J5.00007: Simultaneous conjugate large area atom interferometers for a precision photon recoil measurement Sheng-wey Chiow, Sven Herrmann, Holger Mueller, Steven Chu We report on progress towards a precision measurement of the photon recoil of a cesium atom. We present large area atom interferometers with up to 24-photon Bragg diffraction as beam splitters, which increase the phase shift 12-fold for Mach- Zehnder and 144-fold for Ramsey-Bord\'{e} (RB) geometries. As the atom's internal state is not changed, important systematic effects such as ac Stark shifts and Zeeman shifts can cancel. This dramatic increase in sensitivity and precision opens the door to improved measurements of the fine structure constant, inertial forces, and tests of relativity and quantum electrodynamics. We also demonstrate simultaneous conjugate large area atom interferometers (SCI) in RB geometry for measuring the photon recoil. Conjugate interferometers feature the same phase shift due to local gravity, but opposite phase shift due to the photon recoil. Performing them simultaneously allows a direct measurement of the photon recoil, while local gravity, vibrational noise, and some laser noise are common mode and cancel. We present SCI fringes that determine the recoil frequency with ppm precision in 20 mins integration time. We expect to reach our goal of sub-ppb accuracy in determining the fine structure constant in the near future. [Preview Abstract] |
Thursday, May 29, 2008 12:24PM - 12:36PM |
J5.00008: Compact gravity gradiometry with a Bose-Einstein condensate interferometer K. Jeramy Hughes, Benjamin Deissler, John H.T. Burke, Cass Sackett Atom interferometers are among the best available devices for inertial sensing and gravity gradiometry[1,2]. Unfortunately, these current devices cannot be made compact because many of these techniques require that the atom packets are in free fall over large distances. In our experiments we overcome this limitation by repeatedly applying a pulsed optical lattice to suspend two vertically separated packets of Bose-condensed ${}^ {87}$Rb atoms while keeping them in a state of virtual free fall. Drop distances are negligible and after multiple pulses, the packets are recombined and an interference signal is observed. We will discuss our progress and experimental results. [1] A. Peters, K.Y. Chung, and S. Chu. Metrologia 38, 25 (2001) [2] J. M. McGuirk, G. T. Foster, J. B. Fixler, M. J. Snadden, and M. A. Kasevich, Phys. Rev. A 65, 033608 (2002). [Preview Abstract] |
Thursday, May 29, 2008 12:36PM - 12:48PM |
J5.00009: Bloch oscillations as a probe of the local gravitational field during optical lattice clock operation Brandon Peden, Dominic Meiser, Marilu Chiofalo, Murray Holland Optical lattice clocks are approaching a level of precision where knowledge of the gravitational potential at the location of the clock is necessary in order to compare results from different labs. We propose a scheme to measure the local gravitational acceleration by detecting Bloch oscillations using the lattice beams. Under the influence of gravity, the atoms are accelerated until they reach the Brillouin zone boundary, at which time they are Bragg reflected. The Bragg reflection is accompanied by coherent scattering of photons between the two counter-propagating lattice beams in order to conserve momentum. These scattered photons can be detected without disrupting normal clock operation. [Preview Abstract] |
Thursday, May 29, 2008 12:48PM - 1:00PM |
J5.00010: Cold Atom Cloud Evolution in Optical Tunnels N. Chattrapiban, I.V. Arakelyan, S. Mitra, W.T. Hill, III An optical tunnel is a basic element upon which networks and circuits (e.g., SQUIDS, transmission lines, etc.) for ultra-cold neutral atoms can be built. Optical tunnels can be formed with light tuned blue or red of strong transitions, typically involving ground state atoms. For these elements to be useful, negative influences, particularly those related to decoherence, must be nonexistence. We have investigated some aspects of the cloud-tunnel dynamics. Specifically, we have monitored cloud evolution quantitatively and modeled its dynamics in steady-state with Boltzmann's equation. We find that by an appropriate adjustment of the tunnel potential relative to the cloud temperature, significant transverse cooling of the cloud is possible; a reduction in the temperature by a factor of 10 was observed. This leads to a very directional cloud of atoms with a density distribution across the tunnel that has a small curvature, which may be useful in atom interferometry. These and other results will be presented. [Preview Abstract] |
Thursday, May 29, 2008 1:00PM - 1:12PM |
J5.00011: Conservation of momentum and the Aharonov-Bohm Effect Adam Caprez, Herman Batelaan The Aharonov-Bohm Effect serves as an example of a purely quantum mechanical phenomenon in which classical forces on the electron are thought to vanish. The presence of forces is still an ongoing debate [1,2]. Surprisingly, a complete special relativistic treatment of the forces in the electron-solenoid system has never been done [3]. We present our ongoing theoretical work on the issue, and explore a connection between Feynman's well-known example [3] of two moving point charges and the Aharonov-Bohm Effect. The relation between this theoretical work and our earlier experimental results [4] is also discussed. [1] T.H. Boyer, J. Phys. A. \textbf{39, } 3455 (2006). [2] G.C. Hegerfeldt and J.T. Neumann, [quant-ph] arXiv:0801.0799v1 (2008). [3] Y. Aharonov and D. Rohrlich, \textit{Quantum Paradoxes: Quantum Theory for the Perplexed} (Wiley-VCH, Weinheim, 2005). [4] \textit{The Feynman Lectures on Physics}. Vol. II, pp. 26-2-26-5 (1964). [5] A. Caprez, B. Barwick, and H. Batelaan. Phys. Rev. Lett. \textbf{99}, 210401 (2007). [Preview Abstract] |
Thursday, May 29, 2008 1:12PM - 1:24PM |
J5.00012: Searching for Massive Photons with Ion Interferometry Dallin Durfee, Brian Neyenhuis, Dan Christensen We will discuss an ion interferometer under construction that should enable the detection of a possible photon rest mass more than 100 times smaller than previous laboratory experiments. In the apparatus a beam of $^{87}$Sr$^+$ ions will be split and recombined using stimulated Raman transitions inside of a conducting cylinder. Deviations from Coulomb's law can then be detected by measuring the phase shift of the interferometer as the potential applied to the conducting cylinder is changed. We will discuss both the details of the device and the theory connecting deviations from Coulomb's inverse-square law to a theory of massive photons. [Preview Abstract] |
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