271 research outputs found
Polariton Squeezing in Semiconductor Microcavities
We report squeezed polariton generation using parametric polariton four-wave
mixing in semiconductor microcavities in the strong coupling regime. The
geometry of the experiment corresponds to degenerate four-wave mixing, which
gives rise to a bistability threshold. Spatial effects in the nonlinear regime
are evidenced, and spatial filtering is required in order to optimize the
measured squeezing. By measuring the noise of the outgoing light, we infer a 9
percent squeezing on the polariton field close to the bistability turning
point
Optical nonlinear dynamics with cold atoms in a cavity
This paper presents the nonlinear dynamics of laser cooled and trapped cesium
atoms placed inside an optical cavity and interacting with a probe light beam
slightly detuned from the 6S1/2(F=4) to 6P3/2(F=5) transition. The system
exhibits very strong bistability and instabilities. The origin of the latter is
found to be a competition between optical pumping and non-linearities due to
saturation of the optical transition.Comment: 6 pages, 7 figures, LaTe
Reversible Quantum Interface for Tunable Single-sideband Modulation
Using Electromagnetically Induced Transparency (EIT) in a Cesium vapor, we
demonstrate experimentally that the quantum state of a light beam can be mapped
into the long lived Zeeman coherences of an atomic ground state. Two
non-commuting variables carried by light are simultaneously stored and
subsequentely read-out, with no noise added. We compare the case where a
tunable single sideband is stored independently of the other one to the case
where the two symmetrical sidebands are stored using the same EIT transparency
window.Comment: 4 pages, 6 figure
Dynamical Quantum Memories
We propose a dynamical approach to quantum memories using an
oscillator-cavity model. This overcomes the known difficulties of achieving
high quantum input-output fidelity with storage times long compared to the
input signal duration. We use a generic model of the memory response, which is
applicable to any linear storage medium ranging from a superconducting device
to an atomic medium. The temporal switching or gating of the device may either
be through a control field changing the coupling, or through a variable
detuning approach, as in more recent quantum memory experiments. An exact
calculation of the temporal memory response to an external input is carried
out. This shows that there is a mode-matching criterion which determines the
optimum input and output mode shape. This optimum pulse shape can be modified
by changing the gate characteristics. In addition, there is a critical coupling
between the atoms and the cavity that allows high fidelity in the presence of
long storage times. The quantum fidelity is calculated both for the coherent
state protocol, and for a completely arbitrary input state with a bounded total
photon number. We show how a dynamical quantum memory can surpass the relevant
classical memory bound, while retaining a relatively long storage time.Comment: 16 pages, 9 figure
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