3,257 research outputs found
Quantum theory of a polarization phase-gate in an atomic tripod configuration
We present the quantum theory of a polarization phase-gate that can be
realized in a sample of ultracold rubidium atoms driven into a tripod
configuration. The main advantages of this scheme are in its relative
simplicity and inherent symmetry. It is shown that the conditional phase shifts
of order can be attained.Comment: X International Conference on Quantum Optics, Minsk, Belaru
Polarization phase gate with a tripod atomic system
We analyze the nonlinear optical response of a four-level atomic system
driven into a tripod configuration. The large cross-Kerr nonlinearities that
occurr in such a system are shown to produce nonlinear phase shift of order
. Such a substantial shift may be observed in a cold atomic gas in a
magneto-optical trap where it coupl be fasibly exploited towards the
realization of a polarization quantum phase gate. The experimental feasibility
of such a gate is here examined in detail.Comment: Corrected versio
Phonon Squeezed States Generated by Second Order Raman Scattering
We study squeezed states of phonons, which allow a reduction in the quantum
fluctuations of the atomic displacements to below the zero-point quantum noise
level of coherent phonon states. We investigate the generation of squeezed
phonon states using a second order Raman scattering process. We calculate the
expectation values and fluctuations of both the atomic displacement and the
lattice amplitude operators, as well as the effects of the phonon squeezed
states on macroscopically measurable quantities, such as changes in the
dielectric constant. These results are compared with recent experiments.Comment: 4 pages, REVTE
Statistics of Raman-Active Excitations via Masurement of Stokes-Anti-Stokes Correlations
A general fundamental relation connecting the correlation of Stokes and
anti-Stokes modes to the quantum statistical behavior of vibration and pump
modes in Raman-active materials is derived. We show that under certain
conditions this relation can be used to determine the equilibrium number
variance of phonons.Time and temperature ranges for which such conditions can
be satisfied are studied and found to be available in todays' experimental
standards. Furthermore, we examine the results in the presence of multi-mode
pump as well as for the coupling of pump to the many vibration modes and
discuss their validity in these cases.Comment: 12 pages, 1 figure, accepted for publication in Phys.Rev.
Driving the atom by atomic fluorescence: analytic results for the power and noise spectra
We study how the spectral properties of resonance fluorescence propagate
through a two-atom system. Within the weak-driving-field approximation we find
that, as we go from one atom to the next, the power spectrum exhibits both
sub-natural linewidth narrowing and large asymmetries while the spectrum of
squeezing narrows but remains otherwise unchanged. Analytical results for the
observed spectral features of the fluorescence are provided and their origin is
thoroughly discussed.Comment: 13 pages, 5 figures; to be published in Phys. Rev. A Changed title
and conten
In-situ velocity imaging of ultracold atoms using slow--light
The optical response of a moving medium suitably driven into a slow-light
propagation regime strongly depends on its velocity. This effect can be used to
devise a novel scheme for imaging ultraslow velocity fields. The scheme turns
out to be particularly amenable to study in-situ the dynamics of collective and
topological excitations of a trapped Bose-Einstein condensate. We illustrate
the advantages of using slow-light imaging specifically for sloshing
oscillations and bent vortices in a stirred condensate
Adiabatic steering and determination of dephasing rates in double dot qubits
We propose a scheme to prepare arbitrary superpositions of quantum states in
double quantum--dots irradiated by coherent microwave pulses. Solving the
equations of motion for the dot density matrix, we find that dephasing rates
for such superpositions can be quantitatively infered from additional electron
current pulses that appear due to a controllable breakdown of coherent
population trapping in the dots.Comment: 5 pages, 4 figures. To appear in Phys. Rev.
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