89 research outputs found
Slow-light pulses in moving media
Slow light in moving media reaches a paradoxical regime when the flow speed
of the medium approaches the group velocity of light. Pulses can penetrate a
region where a counter-propagating flow exceeds the group velocity. When the
counter-flow slows down pulses are reflected
Quantum cloning at the light-atoms interface: copying a coherent light state into two atomic quantum memories
A scheme for the optimal Gaussian cloning of coherent light states at the
light-atoms interface is proposed. The distinct feature of this proposal is
that the clones are stored in an atomic quantum memory, which is important for
applications in quantum communication. The atomic quantum cloning machine
requires only a single passage of the light pulse through the atomic ensembles
followed by the measurement of a light quadrature and an appropriate feedback,
which renders the protocol experimentally feasible. An alternative protocol,
where one of the clones is carried by the outgoing light pulse, is discussed in
connection with quantum key distribution.Comment: 4 pages, 3 figures, RevTeX
Single-passage read-out of atomic quantum memory
A scheme for retrieving quantum information stored in collective atomic spin
systems onto optical pulses is presented. Two off-resonant light pulses cross
the atomic medium in two orthogonal directions and are interferometrically
recombined in such a way that one of the outputs carries most of the
information stored in the medium. In contrast to previous schemes our approach
requires neither multiple passes through the medium nor feedback on the light
after passing the sample which makes the scheme very efficient. The price for
that is some added noise which is however small enough for the method to beat
the classical limits.Comment: 8 pages, 2 figures, RevTeX
Conditional generation of arbitrary single-mode quantum states of light by repeated photon subtractions
We propose a scheme for the conditional generation of arbitrary finite
superpositions of (squeezed) Fock states in a single mode of a traveling
optical field. The suggested setup requires only a source of squeezed states,
beam splitters, strong coherent beams, and photodetectors with single-photon
sensitivity. The method does not require photodetectors with a high efficiency
nor with a single-photon resolution.Comment: 9 pages, 9 figures, RevTeX
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