682 research outputs found
Cavity-QED tests of representations of canonical commutation relations employed in field quantization
Various aspects of dissipative and nondissipative decoherence of Rabi
oscillations are discussed in the context of field quantization in alternative
representations of CCR. Theory is confronted with experiment, and a possibility
of more conclusive tests is analyzed.Comment: Discussion of dissipative and nondissipative decoherence is included.
Theory is now consistent with the existing data and predictions for new
experiments are more reliabl
Generalization of the Einstein coefficients and rate equations under the quantum Rabi oscillation
We have generalized Einstein coefficients and rate equations from quantum
field theoretic point of view by bringing the fundamental processes and the
quantum Rabi oscillation in a single footing for the light-matter interactions
for nonzero Rabi frequency. We have analytically obtained multimode
Jaynes-Cummings model results for the quantum Rabi oscillations of a two-level
system in a lossy resonant cavity containing (i) thermal photons and (ii)
injected photons of a coherent field. We have renormalized the coupling
constant for the light-matter interactions for these cases. Our results match
well with the seminal experimental data obtained in this regard by Brune et al
[Phys. Rev. Lett 76, 1800 (1996)]. We also have studied the population dynamics
in this regard by applying the generalized Einstein rate equations.Comment: 11 pages, 4 figures; We have corrected the Q-factor for the dotted
line of figure 2-
Theory versus experiment for vacuum Rabi oscillations in lossy cavities
The 1996 Brune {\it et al.} experiment on vacuum Rabi oscillation is analyzed
by means of alternative models of atom-reservoir interaction. Agreement with
experimental Rabi oscillation data can be obtained if one defines jump
operators in the dressed-state basis, and takes into account thermal
fluctuations between dressed states belonging to the same manifold. Such
low-frequency transitions could be ignored in a closed cavity, but the cavity
employed in the experiment was open, which justifies our assumption. The cavity
quality factor corresponding to the data is , whereas
reported in the experiment was . The rate of decoherence arising
from opening of the cavity can be of the same order as an analogous correction
coming from finite time resolution (formally equivalent to
collisional decoherence). Peres-Horodecki separability criterion shows that the
rate at which the atom-field state approaches a separable state is controlled
by fluctuations between dressed states from the same manifold, and not by the
rate of transitions towards the ground state. In consequence, improving the
factor we do not improve the coherence properties of the cavity.Comment: typo in eq. (60) corrected; (older comments: 14 figures (1 added),
value of Q improved, a section on the Peres-Horodecki test of separability
added, various small improvements; v3 includes discussion of finite time
resolution, v4 includes microscopic derivation of the master equation
Heterodyne non-demolition measurements on cold atomic samples: towards the preparation of non-classical states for atom interferometry
We report on a novel experiment to generate non-classical atomic states via
quantum non-demolition (QND) measurements on cold atomic samples prepared in a
high finesse ring cavity. The heterodyne technique developed for the QND
detection exhibits an optical shot-noise limited behavior for local oscillator
optical power of a few hundred \muW, and a detection bandwidth of several GHz.
This detection tool is used in single pass to follow non destructively the
internal state evolution of an atomic sample when subjected to Rabi
oscillations or a spin-echo interferometric sequence.Comment: 23 page
Non-perturbative Dynamical Casimir Effect in Optomechanical Systems: Vacuum Casimir-Rabi Splittings
We study the dynamical Casimir effect using a fully quantum-mechanical
description of both the cavity field and the oscillating mirror. We do not
linearize the dynamics, nor do we adopt any parametric or perturbative
approximation. By numerically diagonalizing the full optomechanical
Hamiltonian, we show that the resonant generation of photons from the vacuum is
determined by a ladder of mirror-field {\em vacuum Rabi splittings}. We find
that vacuum emission can originate from the free evolution of an initial pure
mechanical excited state, in analogy with the spontaneous emission from excited
atoms. By considering a coherent drive of the mirror, using a master-equation
approach to take losses into account, we are able to study the dynamical
Casimir effect for optomechanical coupling strengths ranging from weak to
ultrastrong. We find that a resonant production of photons out of the vacuum
can be observed even for mechanical frequencies lower than the cavity-mode
frequency. Since high mechanical frequencies, which are hard to achieve
experimentally, were thought to be imperative for realizing the dynamical
Casimir effect, this result removes one of the major obstacles for the
observation of this long-sought effect. We also find that the dynamical Casimir
effect can create entanglement between the oscillating mirror and the radiation
produced by its motion in the vacuum field, and that vacuum Casimir-Rabi
oscillations can occur.Comment: 30 pages, 8 figure
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