8,797 research outputs found
Efficient generation of distant atom entanglement
We show how the entanglement of two atoms, trapped in distant separate
cavities, can be generated with arbitrarily high probability of success. The
scheme proposed employs sudden excitation of the atoms proving that the weakly
driven condition is not necessary to obtain the success rate close to unity.
The modified scheme works properly even if each cavity contains many atoms
interacting with the cavity modes. We also show that our method is robust
against the spontaneous atomic decay.Comment: 4 pages, 5 figure
Entangled-state cycles from conditional quantum evolution
A system of cascaded qubits interacting via the oneway exchange of photons is
studied. While for general operating conditions the system evolves to a
superposition of Bell states (a dark state) in the long-time limit, under a
particular resonance condition no steady state is reached within a finite time.
We analyze the conditional quantum evolution (quantum trajectories) to
characterize the asymptotic behavior under this resonance condition. A distinct
bimodality is observed: for perfect qubit coupling, the system either evolves
to a maximally entangled Bell state without emitting photons (the dark state),
or executes a sustained entangled-state cycle - random switching between a pair
of Bell states while emitting a continuous photon stream; for imperfect
coupling, two entangled-state cycles coexist, between which a random selection
is made from one quantum trajectory to another.Comment: 12 pages, 10 figure
Quantum Teleportation of Light
Requirements for the successful teleportation of a beam of light, including
its temporal correlations, are discussed. Explicit expressions for the degrees
of first- and second-order optical coherence are derived. Teleportation of an
antibunched photon stream illustrates our results.Comment: 4 pages, 5 figure
Teleportation with insurance of an entangled atomic state via cavity decay
We propose a scheme to teleport an entangled state of two -type
three-level atoms via photons. The teleportation protocol involves the local
redundant encoding protecting the initial entangled state and allowing for
repeating the detection until quantum information transfer is successful. We
also show how to manipulate a state of many -type atoms trapped in a
cavity.Comment: 8 pages, 5 figure
Effect of atomic beam alignment on photon correlation measurements in cavity QED
Quantum trajectory simulations of a cavity QED system comprising an atomic
beam traversing a standing-wave cavity are carried out. The delayed photon
coincident rate for forwards scattering is computed and compared with the
measurements of Rempe et al. [Phys. Rev. Lett. 67, 1727 (1991)] and Foster et
al. [Phys. Rev. A 61, 053821 (2000)]. It is shown that a moderate atomic beam
misalignment can account for the degradation of the predicted correlation. Fits
to the experimental data are made in the weak-field limit with a single
adjustable parameter--the atomic beam tilt from perpendicular to the cavity
axis. Departures of the measurement conditions from the weak-field limit are
discussed.Comment: 15 pages and 13 figure
A MULTIPLE ORGANIC POLLUTANT SIMULATION/OPTIMIZATION MODEL OF INDUSTRIAL AND MUNICIPAL WASTEWATER LOADING TO A RIVERINE ENVIRONMENT
A multiple organic pollutant simulation/optimization model is developed to aid policy analysis of least cost approaches to wastewater management. Downstream impacts vary non-linearly with pollution loads due to non-linear constituent interactions. An iterative solution method is necessary. The model is demonstrated using a case study of the Nitra River Basin in Slovakia.Environmental Economics and Policy, Research Methods/ Statistical Methods,
From quantum feedback to probabilistic error correction: Manipulation of quantum beats in cavity QED
It is shown how to implement quantum feedback and probabilistic error
correction in an open quantum system consisting of a single atom, with ground-
and excited-state Zeeman structure, in a driven two-mode optical cavity. The
ground state superposition is manipulated and controlled through conditional
measurements and external fields, which shield the coherence and correct
quantum errors. Modeling of an experimentally realistic situation demonstrates
the robustness of the proposal for realization in the laboratory
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