1,877 research outputs found
Effective mass in quantum effects of radiation pressure
We study the quantum effects of radiation pressure in a high-finesse cavity
with a mirror coated on a mechanical resonator. We show that the optomechanical
coupling can be described by an effective susceptibility which takes into
account every acoustic modes of the resonator and their coupling to the light.
At low frequency this effective response is similar to a harmonic response with
an effective mass smaller than the total mass of the mirror. For a plano-convex
resonator the effective mass is related to the light spot size and becomes very
small for small optical waists, thus enhancing the quantum effects of
optomechanical coupling.Comment: 11 pages, 4 figures, RevTe
Atomic quantum memory: cavity vs single pass schemes
This paper presents a quantum mechanical treatment for both atomic and field
fluctuations of an atomic ensemble interacting with propagating fields, either
in Electromagnetically Induced Transparency or in a Raman situation. The atomic
spin noise spectra and the outgoing field spectra are calculated in both
situations. For suitable parameters both EIT and Raman schemes efficiently
preserve the quantum state of the incident probe field in the transfer process
with the atoms, although a single pass scheme is shown to be intrinsically less
efficient than a cavity scheme
Quantum limits of cold damping with optomechanical coupling
Thermal noise of a mirror can be reduced by cold damping. The displacement is
measured with a high-finesse cavity and controlled with the radiation pressure
of a modulated light beam. We establish the general quantum limits of noise in
cold damping mechanisms and we show that the optomechanical system allows to
reach these limits. Displacement noise can be arbitrarily reduced in a narrow
frequency band. In a wide-band analysis we show that thermal fluctuations are
reduced as with classical damping whereas quantum zero-point fluctuations are
left unchanged. The only limit of cold damping is then due to zero-point energy
of the mirrorComment: 10 pages, 3 figures, RevTe
Teleportation of an atomic ensemble quantum state
We propose a protocol to achieve high fidelity quantum state teleportation of
a macroscopic atomic ensemble using a pair of quantum-correlated atomic
ensembles. We show how to prepare this pair of ensembles using quasiperfect
quantum state transfer processes between light and atoms. Our protocol relies
on optical joint measurements of the atomic ensemble states and magnetic
feedback reconstruction
Quantum state transfer between field and atoms in Electromagnetically Induced Transparency
We show that a quasi-perfect quantum state transfer between an atomic
ensemble and fields in an optical cavity can be achieved in Electromagnetically
Induced Transparency (EIT). A squeezed vacuum field state can be mapped onto
the long-lived atomic spin associated to the ground state sublevels of the
Lambda-type atoms considered. The EIT on-resonance situation show interesting
similarities with the Raman off-resonant configuration. We then show how to
transfer the atomic squeezing back to the field exiting the cavity, thus
realizing a quantum memory-type operation.Comment: 8 pages, 4 figure
Dynamics of a pulsed continuous variable quantum memory
We study the transfer dynamics of non-classical fluctuations of light to the
ground-state collective spin components of an atomic ensemble during a pulsed
quantum memory sequence, and evaluate the relevant physical quantities to be
measured in order to characterize such a quantum memory. We show in particular
that the fluctuations stored into the atoms are emitted in temporal modes which
are always different than those of the readout pulse, but which can
nevertheless be retrieved efficiently using a suitable temporal mode-matching
technique. We give a simple toy model - a cavity with variable transmission -
which accounts for the behavior of the atomic quantum memory.Comment: 6 pages, 5 figure
Optical phase-space reconstruction of mirror position at the attometer level
We describe an experiment in which the quadratures of the position of an
harmonically-bound mirror are observed at the attometer level. We have studied
the Brownian motion of the mirror, both in the free regime and in the
cold-damped regime when an external viscous force is applied by radiation
pressure. We have also studied the thermal-noise squeezing when the external
force is parametrically modulated. We have observed both the 50% theoretical
limit of squeezing at low gain and the parametric oscillation of the mirror for
a large gain.Comment: 10 pages, 11 figure
Entanglement storage in atomic ensembles
We propose to entangle macroscopic atomic ensembles in cavity using
EPR-correlated beams. We show how the field entanglement can be almost
perfectly mapped onto the long-lived atomic spins associated with the ground
states of the ensembles, and how it can be retrieved in the fields exiting the
cavities after a variable storage time. Such a continuous variable quantum
memory is of interest for manipulating entanglement in quantum networks
Continuous variable entanglement using cold atoms
We present experimental demonstration of quadrature and polarization
entanglement generated via the interaction between a coherent linearly
polarized field and cold atoms in a high finesse optical cavity. The non linear
atom-field interaction produces two squeezed modes with orthogonal
polarizations which are used to generate a pair of non separable beams, the
entanglement of which is demonstrated by checking the inseparability criterion
for continuous variables recently derived by Duan et al. [Phys. Rev. Lett. 84,
2722 (2000)] and calculating the entanglement of formation [Giedke et al.,
Phys. Rev. Lett. 91, 107901 (2003)]
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