100 research outputs found
Laser and microwave spectroscopy of even-parity Rydberg states of neutral ytterbium and Multichannel Quantum Defect Theory analysis
New measurements of high-lying even parity and
levels of neutral Yb are presented in this paper.
Spectroscopy is performed by a two-step laser excitation from the ground state
, and the Rydberg levels are detected by using the
field ionization method. Additional two-photon microwave spectroscopy is used
to improve the relative energy accuracy where possible. The spectroscopic
measurements are complemented by a multichannel quantum defect theory (MQDT)
analysis for the J=0 and the two-coupled J=2 even parity series. We compare our
results with the previous analysis of Aymar {\it{et al}} \cite{Aymar_1980} and
analyze the observed differences. From the new MQDT models, a revised value for
the first ionization limit cm is proposed.Comment: 15 pages, 3 figure
Observation of a resonant four-body interaction in cold cesium Rydberg atoms
Cold Rydberg atoms subject to long-range dipole-dipole interactions represent
a particularly interesting system for exploring few-body interactions and
probing the transition from 2-body physics to the many-body regime. In this
work we report the direct observation of a resonant 4-body Rydberg interaction.
We exploit the occurrence of an accidental quasi-coincidence of a 2-body and a
4-body resonant Stark-tuned Forster process in cesium to observe a resonant
energy transfer requiring the simultaneous interaction of at least four
neighboring atoms. These results are relevant for the implementation of quantum
gates with Rydberg atoms and for further studies of many-body physics.Comment: 5 pages, 5 figure
Time-resolved Observation and Control of Superexchange Interactions with Ultracold Atoms in Optical Lattices
Quantum mechanical superexchange interactions form the basis of quantum
magnetism in strongly correlated electronic media. We report on the direct
measurement of superexchange interactions with ultracold atoms in optical
lattices. After preparing a spin-mixture of ultracold atoms in an
antiferromagnetically ordered state, we measure a coherent
superexchange-mediated spin dynamics with coupling energies from 5 Hz up to 1
kHz. By dynamically modifying the potential bias between neighboring lattice
sites, the magnitude and sign of the superexchange interaction can be
controlled, thus allowing the system to be switched between antiferromagnetic
or ferromagnetic spin interactions. We compare our findings to predictions of a
two-site Bose-Hubbard model and find very good agreement, but are also able to
identify corrections which can be explained by the inclusion of direct
nearest-neighbor interactions.Comment: 24 pages, 7 figure
High-fidelity gates via RF-induced F\"{o}rster resonances
Registers of trapped neutral atoms, excited to Rydberg states to induce
strong long-distance interactions, are extensively studied for direct
applications in quantum computing. In this regard, new effective approaches to
the creation of multiqubit quantum gates arise high interest. Here, we present
a novel gate implementation technique based on RF-induced few-body F\"{o}rster
resonances. External radio frequency (RF) control field allows us to manipulate
the phase and population dynamics of many-atom system, thus enabling the
realization of universal quantum gates. We numerically
demonstrate RF-induced resonant interactions, as well as high-precision
three-qubit gates. The extreme controllability of interactions provided by RF
makes it possible to implement gates for a wide range of parameters of the
atomic system, and significantly facilitates their experimental implementation.
For the considered error sources, we achieve theoretical gate fidelities
compatible with error correction () using reasonable experimental
parameters.Comment: 6 pages, 3 figures, 1 tabl
Influence of lasers propagation delay on the sensitivity of atom interferometers
In atom interferometers based on two photon transitions, the delay induced by
the difference of the laser beams paths makes the interferometer sensitive to
the fluctuations of the frequency of the lasers. We first study, in the general
case, how the laser frequency noise affects the performance of the
interferometer measurement. Our calculations are compared with the measurements
performed on our cold atom gravimeter based on stimulated Raman transitions. We
finally extend this study to the case of cold atom gradiometers.Comment: 17 pages, 6 figure
Low noise amplication of an optically carried microwave signal: application to atom interferometry
In this paper, we report a new scheme to amplify a microwave signal carried
on a laser light at =852nm. The amplification is done via a
semiconductor tapered amplifier and this scheme is used to drive stimulated
Raman transitions in an atom interferometer. Sideband generation in the
amplifier, due to self-phase and amplitude modulation, is investigated and
characterized. We also demonstrate that the amplifier does not induce any
significant phase-noise on the beating signal. Finally, the degradation of the
performances of the interferometer due to the amplification process is shown to
be negligible
Measurement of the sensitivity function in time-domain atomic interferometer
submitted to IEEE Trans. Instrum. Meas.We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave-packets. The sensitivity function is calculated in the case of a three pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at BNM-SYRTE. We successfully compare this calculation to experimental measurements. The sensitivity of the interferometer is limited by the phase noise of the lasers, as well as by residual vibrations. We evaluate the performance that could be obtained with state of the art quartz oscillators, as well as the impact of the residual phase noise of the phase-lock loop. Requirements on the level of vibrations is derived from the same formalism
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