Papers by Tzahi Grünzweig
J Opt B Quantum Semicl Opt, 2005
We perform spectroscopy on the ground-state hyperfine splitting of 85Rb atoms trapped in far-off-... more We perform spectroscopy on the ground-state hyperfine splitting of 85Rb atoms trapped in far-off-resonance optical traps. The existence of a spatially dependent shift in the energy levels is shown to induce an inherent dephasing effect, which causes a broadening of the spectroscopic line and hence an inhomogeneous loss of atomic coherence at a much faster rate than the homogeneous one caused by spontaneous photon scattering. We present here a number of approaches for reducing this inhomogeneous broadening, based on trap geometry, additional laser fields, and novel microwave pulse sequences. We then show how hyperfine spectroscopy can be used to study the quantum dynamics of optically trapped atoms.
Physical Review A, 2004
The decay in the hyperfine coherence of optically trapped atoms due to interactions with the envi... more The decay in the hyperfine coherence of optically trapped atoms due to interactions with the environment, is only partly suppressed by "echo" spectroscopy [M. F. Andersen et al. Phys. Rev. Lett. 90, 023001 (2003)], primarily due to dynamical (time-dependent) dephasing mechanisms. We demonstrate here an improved pulse sequence, for which the decay of coherence is reduced by a factor of 2.5 beyond the reduction offered by the "echo" spectroscopy. This reduction occurs when each dark period in-between pulses is shorter than the time scale over which substantial dephasing develops. The coherence time is then limited by mixing to other vibrational levels in the trap and, to a lesser extent, the lifetime of the internal states of the atoms.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies, 2004
The loss in coherence in a trapped-atoms "echo" experiment is suppressed by a different pulse seq... more The loss in coherence in a trapped-atoms "echo" experiment is suppressed by a different pulse sequence. The coherence time is then limited by mixing to other vibrational levels and the lifetime of the internal states.
2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim, 2011
The fact that a single neutral atom stored in an optical micro-trap is very well isolated from th... more The fact that a single neutral atom stored in an optical micro-trap is very well isolated from the environment makes it attractive for application in a quantum logic device. Scaling such a device requires a consistent and efficient method of loading a single atom into the micro-trap. By inducing light-assisted collisions between trapped pairs of atoms we observe the outcome of individual collision events. This allowed us to devise a method that enables a loading efficiency of 83% of a single atom into a micro-trap. Furthermore, we are able to accurately count the small number of atoms using fluorescence imaging at high densities while minimizing loss through light assisted collisions.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
Review of Scientific Instruments, 2012
We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By a... more We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By applying a high current (15 A) pulse to the dispenser at room temperature we can rapidly heat it to a temperature at which it starts dispensing, avoiding the need for preheating. The atomic beam produced is capable of loading 90% of a magneto-optical trap (MOT) in less than 7 s while maintaining a low vacuum pressure of <10(-11) Torr. The transverse velocity components of the atomic beam are measured to be within typical capture velocities of a rubidium MOT. Finally, we show that the atomic beam can be turned off within 1.8 s.
Quantum Information Processing, 2011
We count a small number of atoms trapped in an optical microtrap, using fluorescence induced by a... more We count a small number of atoms trapped in an optical microtrap, using fluorescence induced by a standing wave of blue-detuned light. Blue-detuned light limits losses from light-assisted collisions, allowing us to manipulate the trapped atoms further. When a pair of trapped atoms is detected in this way, we apply a tailored laser light pulse to induce light assisted-collisions. We directly observe that these collisions lead to either one or both atoms being lost from the microtrap. By optimizing the frequency and intensity of the laser beam inducing the light-assisted collisions, one atom loss can be made to dominate over pair loss. We demonstrate that in a microtrap occupied by ∼50 atoms, this optimized light-assisted collision pulse can eject all but one atom efficiently. This method may be used to prepare many singly occupied microtraps for a neutral atom based quantum computation device.
Physical Review Letters, 2006
We perform echo spectroscopy on ultra cold atoms in atom optics billiards, to study their quantum... more We perform echo spectroscopy on ultra cold atoms in atom optics billiards, to study their quantum dynamics. The detuning of the trapping laser is used to change the "perturbation", which causes a decay in the echo coherence. Two different regimes are observed: First, a perturbative regime in which the decay of echo coherence is non-monotonic and partial revivals of coherence are observed. These revivals are more pronounced in traps with mixed dynamics as compared to traps where the dynamics is fully chaotic. Next, for stronger perturbations, the decay becomes monotonic and independent of the strength of the perturbation. In this regime no clear distinction can be made between chaotic traps and traps with mixed dynamics.
Physical Review A, 2004
We investigate the coherence properties of thermal atoms confined in optical dipole traps where t... more We investigate the coherence properties of thermal atoms confined in optical dipole traps where the underlying classical dynamics is chaotic. A perturbative expression derived for the coherence of the echo scheme of Anderson et al. [Phys. Rev. Lett. 90, 023001 (2003)] shows that it is a function of the survival probability or fidelity of eigenstates of the motion of the atoms in the trap. The echo coherence and the survival probability display "system specific" features, even when the underlying classical dynamics is chaotic. In particular, partial revivals in the echo signal and the survival probability are found for a small shift of the potential. Next, a "semiclassical" expression for the averaged echo signal is presented and used to calculate the echo signal for atoms in a light sheet wedge billiard. Revivals in the echo coherence are found in this system, indicating that they may be a generic feature of dipole traps.
Optics Letters, 2011
We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipol... more We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipole trap by collecting fluorescence from atoms exposed to a standing wave of light that is blue detuned from resonance. While scattering photons, the atoms are also cooled by a Sisyphus mechanism that results from the spatial variation in light intensity. The use of a small blue detuning limits the losses due to light assisted collisions, thereby making the method suitable for counting several atoms in a microscopic volume.
Nature Physics, 2010
Neutral atoms stored in optical traps are strong candidates for a physical realization of a quant... more Neutral atoms stored in optical traps are strong candidates for a physical realization of a quantum logic device 1,2 . Far off-resonance optical traps provide conservative potentials and excellent isolation from the environment, and they may be arranged to produce arbitrary arrays of traps, where each trap is occupied by a single atom that can be individually addressed 3-6 . At present, significant effort is being expended on developing two-qubit gates based on coupling individual Rydberg atoms in adjacent optical microtraps 7-9 . A major challenge associated with this approach is the reliable generation of single-atom occupancy in each trap, as the loading efficiency in the past experiments has been limited to 50% (refs 4,7,8,10-12). Here we report a loading efficiency of 82.7% in an optical microtrap. We achieve this by manipulating the collisions between pairs of trapped atoms through tailored optical fields and directly observing the resulting single atoms in the trap.
Laser Physics Letters, 2012
We create two overlapping one-dimensional optical lattices using a single laser beam, a spatial l... more We create two overlapping one-dimensional optical lattices using a single laser beam, a spatial light modulator and a high numerical aperture lens. These lattices have the potential to trap single atoms, and using the dynamic capabilities of the spatial light modulator may shift and sort atoms to a minimum atom-atom separation of 1.52 µm. We show how a simple feedback circuit can compensate for the spatial light modulator's intensity modulation.
Communications in Nonlinear Science and Numerical Simulation, 2003
We discuss a recently demonstrated type of microwave spectroscopy of trapped ultra-cold atoms kno... more We discuss a recently demonstrated type of microwave spectroscopy of trapped ultra-cold atoms known as "echo spectroscopy" [M.F. Andersen et. al., Phys. Rev. Lett., in press (2002)]. Echo spectroscopy can serve as an extremely sensitive experimental tool for investigating quantum dynamics of trapped atoms even when a large number of states are thermally populated. We show numerical results for the stability of eigenstates of an atom-optics billiard of the Bunimovich type, and discuss its behavior under different types of perturbations. Finally, we propose to use special geometrical constructions to make a dephasing free dipole trap.
Journal of Optics B: Quantum and Semiclassical Optics, 2005
We perform spectroscopy on the ground-state hyperfine splitting of 85 Rb atoms trapped in far-off... more We perform spectroscopy on the ground-state hyperfine splitting of 85 Rb atoms trapped in far-off-resonance optical traps. The existence of a spatially dependent shift in the energy levels is shown to induce an inherent dephasing effect, which causes a broadening of the spectroscopic line and hence an inhomogeneous loss of atomic coherence at a much faster rate than the homogeneous one caused by spontaneous photon scattering. We present here a number of approaches for reducing this inhomogeneous broadening, based on trap geometry, additional laser fields, and novel microwave pulse sequences. We then show how hyperfine spectroscopy can be used to study the quantum dynamics of optically trapped atoms.
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Papers by Tzahi Grünzweig