66 research outputs found
Influence of relaxation on propagation, storage and retrieving of light pulses in electromagnetically induced transparency medium
By solving the self-consistent system of Maxwell and density matrix equations
to the first order with respect to nonadiabaticity, we obtain an analytical
solution for the probe pulse propagation. The conditions for efficient storage
of light are analyzed. The necessary conditions for optical propagation
distance has been obtained.Comment: 7 pages, 7 figure
Transverse localization and slow propagation of light
The effect of finite control beam on the transverse spatial profile of the
slow light propagation in an electromagnetically induced transparency medium is
studied. We arrive at a general criterion in terms of eigenequation, and
demonstrate the existence of a set of localized, stationary transverse modes
for the negative detuning of the probe signal field. Each of these
diffraction-free transverse modes has its own characteristic group velocity,
smaller than the conventional theoretical result without considering the
transverse spatial effect
Quantum Communication and Computing With Atomic Ensembles Using Light-Shift Imbalance Induced Blockade
Recently, we have shown that for conditions under which the so-called
light-shift imbalance induced blockade (LSIIB) occurs, the collective
excitation of an ensemble of a multi-level atom can be treated as a closed two
level system. In this paper, we describe how such a system can be used as a
quantum bit (qubit) for quantum communication and quantum computing.
Specifically, we show how to realize a C-NOT gate using the collective qubit
and an easily accessible ring cavity, via an extension of the so-called
Pellizzari scheme. We also describe how multiple, small-scale quantum computers
realized using these qubits can be linked effectively for implementing a
quantum internet. We describe the details of the energy levels and transitions
in 87Rb atom that could be used for implementing these schemes.Comment: 16 pages, 9 figures. Accepted in Phys. Rev.
Magneto-optical rotation and cross-phase modulation via coherently driven tripod atoms
We study the interaction of a weak probe field, having two orthogonally
polarized components, with an optically dense medium of four-level atoms in a
tripod configuration. In the presence of a coherent driving laser,
electromagnetically induced transparency is attained in the medium,
dramatically enhancing its linear as well as nonlinear dispersion while
simultaneously suppressing the probe field absorption. We present the
semiclassical and fully quantum analysis of the system. We propose an
experimentally feasible setup that can induce large Faraday rotation of the
probe field polarization and therefore be used for ultra-sensitive optical
magnetometry. We then study the Kerr nonlinear coupling between the two
components of the probe, demonstrating a novel regime of symmetric, extremely
efficient cross-phase modulation, capable of fully entangling two single-photon
pulses. This scheme may thus pave the way to photon-based quantum information
applications, such as deterministic all-optical quantum computation, dense
coding and teleportation.Comment: Corrected typo
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
A high-efficiency quantum non-demolition single photon number resolving detector
We discuss a novel approach to the problem of creating a photon number
resolving detector using the giant Kerr nonlinearities available in
electromagnetically induced transparency. Our scheme can implement a photon
number quantum non-demolition measurement with high efficiency (99%)
using less than 1600 atoms embedded in a dielectric waveguide.Comment: 4 pages, 4 figures. Significantly revised. More discussion on the
potential experimental realisatio
Coherent population trapping in ruby crystal at room temperature
Observation of coherent population trapping (CPT) at ground-state Zeeman
sublevels of -ion in ruby is reported. The experiments are performed
at room temperature by using both nanosecond optical pulses and nanosecond
trains of ultrashort pulses. In both cases sharp drops in the resonantly
induced fluorescence are detected as the external magnetic field is varied.
Theoretical analysis of CPT in a transient regime due to pulsed action of
optical pulses is presented.Comment: 4 pages, 4 figures, submitted to PR
Dark States and Coherent Control of Spin States in Molecular Magnets
We propose a scheme to realize coherent control of spin states of molecule
magnet, Ni. We introduce transverse magnetic fields with special
frequencies. When the frequencies of transverse magnetic fields match in some
conditions, we obtain dark states in Ni molecules. Through adjusting the
magnitude of magnetic fields, we can obtain any arbitrary superposition of the
two ground spin states of Ni molecules.Comment: 7 pages, 4 figures. To appear in Physical Review
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