309 research outputs found
Retroactive quantum jumps in a strongly-coupled atom-field system
We investigate a novel type of conditional dynamic that occurs in the
strongly-driven Jaynes-Cummings model with dissipation. Extending the work of
Alsing and Carmichael [Quantum Opt. {\bf 3}, 13 (1991)], we present a combined
numerical and analytic study of the Stochastic Master Equation that describes
the system's conditional evolution when the cavity output is continuously
observed via homodyne detection, but atomic spontaneous emission is not
monitored at all. We find that quantum jumps of the atomic state are induced by
its dynamical coupling to the optical field, in order retroactively to justify
atypical fluctuations in ocurring in the homodyne photocurrent.Comment: 4 pages, uses RevTex, 5 EPS figure
Cat States and Single Runs for the Damped Harmonic Oscillator
We discuss the fate of initial states of the cat type for the damped harmonic
oscillator, mostly employing a linear version of the stochastic Schr\"odinger
equation. We also comment on how such cat states might be prepared and on the
relation of single realizations of the noise to single runs of experiments.Comment: 18, Revte
Generation and evolution of vortex-antivortex pairs in Bose-Einstein condensates
We propose a method for generating and controlling a spatially separated
vortex--antivortex pair in a Bose-Einstein condensate trapped in a toroidal
potential. Our simulations of the time dependent Gross-Pitaevskii equation show
that in toroidal condensates vortex dynamics are different from the dynamics in
the homogeneous case. Our numerical results agree well with analytical
calculations using the image method. Our proposal offers an effective example
of coherent generation and control of vortex dynamics in atomic condensates.Comment: 4 pages, 2 figure
New method to simulate quantum interference using deterministic processes and application to event-based simulation of quantum computation
We demonstrate that networks of locally connected processing units with a
primitive learning capability exhibit behavior that is usually only attributed
to quantum systems. We describe networks that simulate single-photon
beam-splitter and Mach-Zehnder interferometer experiments on a causal,
event-by-event basis and demonstrate that the simulation results are in
excellent agreement with quantum theory. We also show that this approach can be
generalized to simulate universal quantum computers.Comment: J. Phys. Soc. Jpn. (in press) http://www.compphys.net/dl
Vortices in a Bose-Einstein Condensate
We have created vortices in two-component Bose-Einstein condensates. The
vortex state was created through a coherent process involving the spatial and
temporal control of interconversion between the two components. Using an
interference technique, we map the phase of the vortex state to confirm that it
possesses angular momentum. We can create vortices in either of the two
components and have observed differences in the dynamics and stability.Comment: 4 pages with 3 figure
Detection of vorticity in Bose-Einstein condensed gases by matter-wave interference
A phase-slip in the fringes of an interference pattern is an unmistakable
characteristic of vorticity. We show dramatic two-dimensional simulations of
interference between expanding condensate clouds with and without vorticity. In
this way, vortices may be detected even when the core itself cannot be
resolved.Comment: 3 pages, RevTeX, plus 6 PostScript figure
Watching a superfluid untwist itself: Recurrence of Rabi oscillations in a Bose-Einstein condensate
The order parameter of a condensate with two internal states can continuously
distort in such a way as to remove twists that have been imposed along its
length. We observe this effect experimentally in the collapse and recurrence of
Rabi oscillations in a magnetically trapped, two-component Bose-Einstein
condensate of ^87Rb
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