698 research outputs found
Storing and releasing light in a gas of moving atoms
We propose a scheme of storing and releasing pulses or cw beams of light in a
moving atomic medium illuminated by two stationary and spatially separated
control lasers. The method is based on electromagnetically induced transparency
(EIT) but in contrast to previous schemes, storage and retrieval of the probe
pulse can be achieved at different locations and without switching off the
control laser.Comment: 4 pages, 3 figures, revised versio
Two-photon linewidth of light "stopping" via electromagnetically induced transparency
We analyze the two-photon linewidth of the recently proposed adiabatic
transfer technique for ``stopping'' of light using electromagnetically induced
transparency (EIT). We shown that a successful and reliable transfer of
excitation from light to atoms and back can be achieved if the spectrum of the
input probe pulse lies within the initial transparency window of EIT, and if
the two-photon detuning is less than the collective coupling strength
(collective vacuum Rabi-frequency) divided by ,
with being the radiative decay rate, the effective number of atoms
in the sample, and the pulse duration. Hence in an optically thick medium
light ``storage'' and retrieval is possible with high fidelity even for systems
with rather large two-photon detuning or inhomogeneous broadening.Comment: 2 figure
Irreversible photon transfer in an ensemble of -type atoms and photon diode
We show that a pair of quantized cavity modes interacting with a spectrally
broadened ensemble of Lambda-type atoms is analogous to an ensemble of two
level systems coupled to a bosonic reservoir. This provides the possibility for
an irreversible photon transfer between photon modes. The density of states as
well as the quantum state of the reservoir can be engineered allowing the
observation of effects such as the quantum Zeno- and anti-Zeno effect, the
destructive interference of decay channels and the decay in a squeezed vacuum.
As a particular application we discuss a photon diode, i.e. a device which
directs a single photon from anyone of two input ports to a common output port.Comment: 5 pages, 2 figure
Limitations of light delay and storage times in EIT experiments with condensates
We investigate the limitations arising from atomic collisions on the storage
and delay times of probe pulses in EIT experiments. We find that the atomic
collisions can be described by an effective decay rate that limits storage and
delay times. We calculate the momentum and temperature dependence of the decay
rate and find that it is necessary to excite atoms at a particular momentum
depending on temperature and spacing of the energy levels involved in order to
minimize the decoherence effects of atomic collisions.Comment: 4 pages RevTeX, 4 figures. Send correspondence to
[email protected]
Towards deterministic optical quantum computation with coherently driven atomic ensembles
Scalable and efficient quantum computation with photonic qubits requires (i)
deterministic sources of single-photons, (ii) giant nonlinearities capable of
entangling pairs of photons, and (iii) reliable single-photon detectors. In
addition, an optical quantum computer would need a robust reversible photon
storage devise. Here we discuss several related techniques, based on the
coherent manipulation of atomic ensembles in the regime of electromagnetically
induced transparency, that are capable of implementing all of the above
prerequisites for deterministic optical quantum computation with single
photons.Comment: 11 pages, 7 figure
A geometric phase gate without dynamical phases
A general scheme for an adiabatic geometric phase gate is proposed which is
maximally robust against parameter fluctuations. While in systems with SU(2)
symmetry geometric phases are usually accompanied by dynamical phases and are
thus not robust, we show that in the more general case of a SU(2) x SU(2)
symmetry it is possible to obtain a non-vanishing geometric phase without
dynamical contributions. The scheme is illustrated for a phase gate using two
systems with dipole-dipole interactions in external laser fields which form an
effective four-level system.Comment: 4 pages, 5 figure
Stationary light in cold atomic gases
We discuss stationary light created by a pair of counter-propagating control
fields in Lambda-type atomic gases with electromagnetically induced
transparency for the case of negligible Doppler broadening. In this case the
secular approximation used in the discussion of stationary light in hot vapors
is no longer valid. We discuss the quality of the effective light-trapping
system and show that in contrast to previous claims it is finite even for
vanishing ground-state dephasing. The dynamics of the photon loss is in general
non exponential and can be faster or slower than in hot gases.Comment: 6 pages, 5 figure
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