1,440 research outputs found
Weak-Light Ultraslow Vector Optical Solitons via Electromagnetically Induced Transparency
We propose a scheme to generate temporal vector optical solitons in a
lifetime broadened five-state atomic medium via electromagnetically induced
transparency. We show that this scheme, which is fundamentally different from
the passive one by using optical fibers, is capable of achieving
distortion-free vector optical solitons with ultraslow propagating velocity
under very weak drive conditions. We demonstrate both analytically and
numerically that it is easy to realize Manakov temporal vector solitons by
actively manipulating the dispersion and self- and cross-phase modulation
effects of the system.Comment: 4 pages, 4 figure
Ultraslow light in inhomogeneously broadened media
We calculate the characteristics of ultraslow light in an inhomogeneously
broadened medium. We present analytical and numerical results for the group
delay as a function of power of the propagating pulse. We apply these results
to explain the recently reported saturation behavior [Baldit {\it et al.}, \prl
{\bf 95}, 143601 (2005)] of ultraslow light in rare earth ion doped crystal.Comment: 4 pages, 5 figure
Stability of atomic clocks based on entangled atoms
We analyze the effect of realistic noise sources for an atomic clock
consisting of a local oscillator that is actively locked to a spin-squeezed
(entangled) ensemble of atoms. We show that the use of entangled states can
lead to an improvement of the long-term stability of the clock when the
measurement is limited by decoherence associated with instability of the local
oscillator combined with fluctuations in the atomic ensemble's Bloch vector.
Atomic states with a moderate degree of entanglement yield the maximal clock
stability, resulting in an improvement that scales as compared to the
atomic shot noise level.Comment: 4 pages, 2 figures, revtex
Distributed Quantum Computation Based-on Small Quantum Registers
We describe and analyze an efficient register-based hybrid quantum
computation scheme. Our scheme is based on probabilistic, heralded optical
connection among local five-qubit quantum registers. We assume high fidelity
local unitary operations within each register, but the error probability for
initialization, measurement, and entanglement generation can be very high
(~5%). We demonstrate that with a reasonable time overhead our scheme can
achieve deterministic non-local coupling gates between arbitrary two registers
with very high fidelity, limited only by the imperfections from the local
unitary operation. We estimate the clock cycle and the effective error
probability for implementation of quantum registers with ion-traps or
nitrogen-vacancy (NV) centers. Our new scheme capitalizes on a new efficient
two-level pumping scheme that in principle can create Bell pairs with
arbitrarily high fidelity. We introduce a Markov chain model to study the
stochastic process of entanglement pumping and map it to a deterministic
process. Finally we discuss requirements for achieving fault-tolerant operation
with our register-based hybrid scheme, and also present an alternative approach
to fault-tolerant preparation of GHZ states.Comment: 22 Pages, 23 Figures and 1 Table (updated references
Legume reaction to soil acidity
Most legumes grow and develop better in neutral soils, with the exception of lupine, which grows at pH 4.0-5.0. Legumes are sensitive to the concentration of aluminium ions in the soi
Nonlinear Optics and Quantum Entanglement of Ultra-Slow Single Photons
Two light pulses propagating with ultra-slow group velocities in a coherently
prepared atomic gas exhibit dissipation-free nonlinear coupling of an
unprecedented strength. This enables a single-photon pulse to coherently
control or manipulate the quantum state of the other. Processes of this kind
result in generation of entangled states of radiation field and open up new
prospectives for quantum information processing
Interferometric probes of many-body localization
We propose a method for detecting many-body localization (MBL) in disordered
spin systems. The method involves pulsed, coherent spin manipulations that
probe the dephasing of a given spin due to its entanglement with a set of
distant spins. It allows one to distinguish the MBL phase from a
non-interacting localized phase and a delocalized phase. In particular, we show
that for a properly chosen pulse sequence the MBL phase exhibits a
characteristic power-law decay reflecting its slow growth of entanglement. We
find that this power-law decay is robust with respect to thermal and disorder
averaging, provide numerical simulations supporting our results, and discuss
possible experimental realizations in solid-state and cold atom systems.Comment: 5 pages, 4 figure
Quantum memory for photons: I. Dark state polaritons
An ideal and reversible transfer technique for the quantum state between
light and metastable collective states of matter is presented and analyzed in
detail. The method is based on the control of photon propagation in coherently
driven 3-level atomic media, in which the group velocity is adiabatically
reduced to zero. Form-stable coupled excitations of light and matter
(``dark-state polaritons'') associated with the propagation of quantum fields
in Electromagnetically Induced Transparency are identified, their basic
properties discussed and their application for quantum memories for light
analyzed.Comment: 13 pages, 6 figures, paragraph on photon echo adde
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