690 research outputs found
A cavity-QED scheme for Heisenberg-limited interferometry
We propose a Ramsey interferometry experiment using an entangled state of N
atoms to reach the Heisenberg limit for the estimation of an atomic phase shift
if the atom number parity is perfectly determined. In a more realistic
situation, due to statistical fluctuations of the atom source and the finite
detection efficiency, the parity is unknown. We then achieve about half the
Heisenberg limit. The scheme involves an ensemble of circular Rydberg atoms
which dispersively interact successively with two initially empty microwave
cavities. The scheme does not require very high-Q cavities. An experimental
realization with about ten entangled Rydberg atoms is achievable with state of
art apparatuses.Comment: 13 pages, 7 figure
Non-classical field state stabilization in a cavity by reservoir engineering
We propose an engineered reservoir inducing the relaxation of a cavity field
towards non-classical states. It is made up of two-level atoms crossing the
cavity one at a time. Each atom-cavity interaction is first dispersive, then
resonant, then dispersive again. The reservoir pointer states are those
produced by an effective Kerr Hamiltonian acting on a coherent field. We
thereby stabilize squeezed states and quantum superpositions of multiple
coherent components in a cavity having a finite damping time. This robust
method could be implemented in state-of-the-art experiments and lead to
interesting insights into mesoscopic quantum state superpositions and into
their protection against decoherence.Comment: submitted to Phys.Rev.Let
Microtraps for neutral atoms using superconducting structures in the critical state
Recently demonstrated superconducting atom-chips provide a platform for
trapping atoms and coupling them to solid-state quantum systems. Controlling
these devices requires a full understanding of the supercurrent distribution in
the trapping structures. For type-II superconductors, this distribution is
hysteretic in the critical state due to the partial penetration of the magnetic
field in the thin superconducting film through pinned vortices. We report here
an experimental observation of this memory effect. Our results are in good
agreement with the redictions of the Bean model of the critical state without
adjustable parameters. The memory effect allows to write and store permanent
currents in micron-sized superconducting structures and paves the way towards
new types of engineered trapping potentials.Comment: accepted in Phys. Rev.
Physique quantique
Recherche Page web : https://www.college-de-france.fr/site/physique-quantique/Presentation.htm. Notre activité s’est orientée en 2017-2018 vers trois directions principales : jeux quantiques dans les multiplicités de Rydberg ; électrodynamique quantique en cavité ; simulation quantique avec les atomes de Rydberg. Nous avons obtenu depuis 2016 des résultats importants dans la première direction, soutenue par un contrat ANR jeune (PI : S. Gleyzes) et un ITN européen (QUSCO). Nous avons en parti..
Non-classical state stabilization in a cavity by reservoir engineering
soumis à Phys.Rev.Lett.We propose an engineered reservoir inducing the relaxation of a cavity field towards non-classical states. It is made up of two-level atoms crossing the cavity one at a time. Each atom-cavity interaction is first dispersive, then resonant, then dispersive again. The reservoir pointer states are those produced by a fictitious Kerr Hamiltonian acting on a coherent field. We thereby stabilize squeezed states and quantum superpositions of multiple coherent components in a cavity having a finite damping time. This robust method could be implemented in state-of-the-art experiments and lead to interesting insights into mesoscopic quantum state superpositions
Coherence-preserving trap architecture for long-term control of giant Rydberg atoms
We present a way to trap a single Rydberg atom, make it long-lived and
preserve an internal coherence over time scales reaching into the minute range.
We propose to trap using carefully designed electric fields, to inhibit the
spontaneous emission in a non resonant conducting structure and to maintain the
internal coherence through a tailoring of the atomic energies using an external
microwave field. We thoroughly identify and account for many causes of
imperfection in order to verify at each step the realism of our proposal.Comment: accepted for publication in PR
Stabilization of nonclassical states of one- and two-mode radiation fields by reservoir engineering
International audienceWe analyze a quantum reservoir engineering method, originally introduced by Sarlette et al. [ Phys. Rev. Lett. 107 010402 (2011)], for the stabilization of nonclassical field states in high-quality cavities. We generalize the method to the protection of mesoscopic entangled field states shared by two nondegenerate field modes. The reservoir consists of a stream of atoms consecutively interacting with the cavity. Each individual atom-cavity interaction follows the same time-varying Hamiltonian, combining resonant with nonresonant parts. We gain detailed insight into the competition between the engineered reservoir and decoherence. We show that the operation is quite insensitive to experimental imperfections and that it could thus be implemented in the near future in the context of microwave cavity or circuit quantum electrodynamics
Spin-motion coupling in a circular Rydberg state quantum simulator: case of two atoms
Rydberg atoms are remarkable tools for the quantum simulation of spin arrays.
Circular Rydberg atoms open the way to simulations over very long time scales,
using a combination of laser trapping of the atoms and spontaneous-emission
inhibition, as shown in the proposal of a XXZ spin-array simulator based on
chains of trapped circular atoms [T.L. Nguyen , Phys. Rev. X
8, 011032 (2018)]. Such simulators could reach regimes (thermalization, glassy
dynamics) that are out of the reach of those based on ordinary,
low-angular-momentum short-lived Rydberg atoms. Over the promised long time
scales, the unavoidable coupling of the spin dynamics with the atomic motion in
the traps may play an important role. We study here the interplay between the
spin exchange and motional dynamics in the simple case of two interacting
circular Rydberg atoms confined in harmonic traps. The time evolution is solved
exactly when the position dependence of the dipole-dipole interaction terms can
be linearized over the extension of the atomic motion. We present numerical
simulations in more complex cases, using the realistic parameters of the
simulator proposal. We discuss three applications. First, we show that
realistic experimental parameters lead to a regime in which atomic and spin
dynamics become fully entangled, generating interesting non-classical motional
states. We also show that, in other parameter regions, the spin dynamics
notably depends on the initial temperature of the atoms in the trap, providing
a sensitive motional thermometry method. Last, and most importantly, we discuss
the range of parameters in which the motion has negligible influence over the
spin dynamics.Comment: 18 pages, 12 figure
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