85 research outputs found
Superluminal Optical Phase Conjugation: Pulse Reshaping and Instability
We theoretically investigate the response of optical phase conjugators to
incident probe pulses. In the stable (sub-threshold) operating regime of an
optical phase conjugator it is possible to transmit probe pulses with a
superluminally advanced peak, whereas conjugate reflection is always
subluminal. In the unstable (above-threshold) regime, superluminal response
occurs both in reflection and in transmission, at times preceding the onset of
exponential growth due to the instability.Comment: 9 pages, 6 figures, RevTex, to appear in Phys. Rev.
Self-induced transparency and giant nonlinearity in doped photonic crystals
Photonic crystals doped with resonant atoms allow for uniquely advantageous
nonlinear modes of optical propagation: (a) Self-induced transparency (SIT)
solitons and multi-dimensional localized "bullets" propagating at photonic band
gap frequencies. These modes can exist even at ultraweak intensities (few
photons) and therefore differ substantially either from solitons in
Kerr-nonlinear photonic crystals or from SIT solitons in uniform media. (b)
Cross-coupling between pulses exhibiting electromagnetically induced
transparency (EIT) and SIT gap solitons. We show that extremely strong
correlations (giant cross-phase modulation) can be formed between the two
pulses. These features may find applications in high-fidelity classical and
quantum optical communications.Comment: 11 pages, 7 figures, to appear in JOSA-
Spin squeezing in nonlinear spin coherent states
We introduce the nonlinear spin coherent state via its ladder operator
formalism and propose a type of nonlinear spin coherent state by the nonlinear
time evolution of spin coherent states. By a new version of spectroscopic
squeezing criteria we study the spin squeezing in both the spin coherent state
and nonlinear spin coherent state. The results show that the spin coherent
state is not squeezed in the x, y, and z directions, and the nonlinear spin
coherent state may be squeezed in the x and y directions.Comment: 4 pages, 2 figs, revised version submitted to J. Opt.
Spatiotemporally localized solitons in resonantly absorbing Bragg reflectors
We predict the existence of spatiotemporal solitons (``light bullets'') in
two-dimensional self-induced transparency media embedded in a Bragg grating.
The "bullets" are found in an approximate analytical form, their stability
being confirmed by direct simulations. These findings suggest new possibilities
for signal transmission control and self-trapping of light.Comment: RevTex, 3 pages, 2 figures, to be published in PR
Coherence and squeezing in superpositions of spin coherent states
We consider the superpositions of spin coherent states and study the
coherence properties and spin squeezing in these states. The spin squeezing is
examined using a new version of spectroscopic squeezing criteria. The results
show that the antibuching effect can be enhanced and spin squeezing can be
generated in the superpositions of two spin coherent states.Comment: 5 pages, 4 figures, revised version submitted to Opt. Commu
Cyclical Quantum Memory for Photonic Qubits
We have performed a proof-of-principle experiment in which qubits encoded in
the polarization states of single-photons from a parametric down-conversion
source were coherently stored and read-out from a quantum memory device. The
memory device utilized a simple free-space storage loop, providing a cyclical
read-out that could be synchronized with the cycle time of a quantum computer.
The coherence of the photonic qubits was maintained during switching operations
by using a high-speed polarizing Sagnac interferometer switch.Comment: 4 pages, 5 figure
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