12,708 research outputs found
Spectrum of light scattering from an extended atomic wave packet
The spectrum of the light scattered from an extended atomic wave packet is
calculated. For a wave packet consisting of two spatially separated peaks
moving on parallel trajectories, the spectrum contains Ramsey-like fringes that
are sensitive to the phase difference between the two components of the wave
packet. Using this technique, one can establish the mutual coherence of the two
components of the wave packet without recombining them.Comment: 4 page
Matter wave interference using two-level atoms and resonant optical fields
A theory of matter wave interference is developed in which resonant optical
fields interact with two-level atoms. When recoil effects are included, spatial
modulation of the atomic density can occur for times that are greater than or
comparable with the inverse recoil frequency. In this regime, the atoms exhibit
matter-wave interference. Two specific atom field geometries are considered. In
the first, atoms characterized by a homogeneous velocity distribution are
subjected to a single radiation pulse. The pulse excites the atoms which then
decay back to the lower state. The spatial modulation of the total atomic
density is calculated as a function of , where is the time following the
pulse. In contrast to the normal Talbot effect, the spatially modulated density
is not a periodic function of owing to spontaneous emission; however,
after a sufficiently long time, the contribution from spontaneous processes no
longer plays a role and the Talbot periodicity is restored. In the second
atom-field geometry, there are two pulses separated by an interval . The
atomic velocity distribution in this case is assumed to be inhomogeneously
broadened. In contrast to the normal Talbot-Lau effect, the spatially modulated
density is not a periodic function of , owing to spontaneous emission;
however, for sufficiently long time, the contribution from spontaneous
processes no longer plays a role and the Talbot periodicity is restored. The
structure of the spatially modulated density is studied, and is found to mirror
the atomic density following the first pulse. The spatially modulated atomic
density serves as an indirect probe of the distribution of spontaneously
emitted radiation.Comment: 14 pages, 3 figure
Influence of qubit displacements on quantum logic operations in a silicon-based quantum computer with constant interaction
The errors caused by qubit displacements from their prescribed locations in
an ensemble of spin chains are estimated analytically and calculated
numerically for a quantum computer based on phosphorus donors in silicon. We
show that it is possible to polarize (initialize) the nuclear spins even with
displaced qubits by using Controlled NOT gates between the electron and nuclear
spins of the same phosphorus atom. However, a Controlled NOT gate between the
displaced electron spins is implemented with large error because of the
exponential dependence of exchange interaction constant on the distance between
the qubits. If quantum computation is implemented on an ensemble of many spin
chains, the errors can be small if the number of chains with displaced qubits
is small
Atomic entanglement generation with reduced decoherence via four-wave mixing
In most proposals for the generation of entanglement in large ensembles of
atoms via projective measurements, the interaction with the vacuum is
responsible for both the generation of the signal that is detected and the spin
depolarization or decoherence. In consequence, one has to usually work in a
regime where the information aquisition via detection is sufficiently slow
(weak measurement regime) such as not to strongly disturb the system. We
propose here a four-wave mixing scheme where, owing to the pumping of the
atomic system into a dark state, the polarization of the ensemble is not
critically affected by spontaneous emission, thus allowing one to work in a
strong measurement regime
Effects of environmental exposures on silicon solar cells
Effect of environmental tests on mechanical and electrical properties of silicon solar cell
Meanfield treatment of Bragg scattering from a Bose-Einstein condensate
A unified semiclassical treatment of Bragg scattering from Bose-Einstein
condensates is presented. The formalism is based on the Gross-Pitaevskii
equation driven by classical light fields far detuned from atomic resonance. An
approximate analytic solution is obtained and provides quantitative
understanding of the atomic momentum state oscillations, as well as a simple
expression for the momentum linewidth of the scattering process. The validity
regime of the analytic solution is derived, and tested by three dimensional
cylindrically symmetric numerical simulations.Comment: 21 pages, 10 figures. Minor changes made to documen
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