2,260 research outputs found
Conditional phase shifts using trapped atoms
We describe a scheme for producing conditional nonlinear phase shifts on
two-photon optical fields using an interaction with one or more ancilla
two-level atomic systems. The conditional field state transformations are
induced by using high efficiency fluorescence shelving measurements on the
atomic ancilla. The scheme can be nearly deterministic and is of obvious
benefit for quantum information applications
Entangling a nanomechanical resonator with a microwave field
We show how the coherent oscillations of a nanomechanical resonator can be
entangled with a microwave cavity in the form of a superconducting coplanar
resonator. Dissipation is included and realistic values for experimental
parameters are estimated.Comment: submitted to J. Mod. Op
Relational time for systems of oscillators
Using an elementary example based on two simple harmonic oscillators, we show
how a relational time may be defined that leads to an approximate Schrodinger
dynamics for subsystems, with corrections leading to an intrinsic decoherence
in the energy eigenstates of the subsystem.Comment: Contribution to the Int. J. of Quant. Info. issue dedicated to the
memory of Asher Pere
Laser phase noise effects on the dynamics of optomechanical resonators
We investigate theoretically the influence of laser phase noise on the
cooling and heating of a generic cavity optomechanical system. We derive the
back-action damping and heating rates and the mechanical frequency shift of the
radiation pressure-driven oscillating mirror, and derive the minimum phonon
occupation number for small laser linewidths. We find that in practice laser
phase noise does not pose serious limitations to ground state cooling. We then
consider the effects of laser phase noise in a parametric cavity driving scheme
that minimizes the back-action heating of one of the quadratures of the
mechanical oscillator motion. Laser linewidths narrow compared to the decay
rate of the cavity field will not pose any problems in an experimental setting,
but broader linewidths limit the practicality of this back-action evasion
method.Comment: 9 pages, 7 figure
Development of a Miniature Electrostatic Accelerometer /MESA/ for low g applications Summary report
Design, fabrication, and testing of miniature digital electrostatic accelerometer for low gravity measurements in spac
Fast and robust two-qubit gates for scalable ion trap quantum computing
We propose a new concept for a two-qubit gate operating on a pair of trapped
ions based on laser coherent control techniques. The gate is insensitive to the
temperature of the ions, works also outside the Lamb-Dicke regime, requires no
individual addressing by lasers, and can be orders of magnitude faster than the
trap period
Heuristic for estimation of multiqubit genuine multipartite entanglement
For every N-qubit density matrix written in the computational basis, an
associated "X-density matrix" can be obtained by vanishing all entries out of
the main- and anti-diagonals. It is very simple to compute the genuine
multipartite (GM) concurrence of this associated N-qubit X-state, which,
moreover, lower bounds the GM-concurrence of the original (non-X) state. In
this paper, we rely on these facts to introduce and benchmark a heuristic for
estimating the GM-concurrence of an arbitrary multiqubit mixed state. By
explicitly considering two classes of mixed states, we illustrate that our
estimates are usually very close to the standard lower bound on the
GM-concurrence, being significantly easier to compute. In addition, while
evaluating the performance of our proposed heuristic, we provide the first
characterization of GM-entanglement in the steady states of the driven Dicke
model at zero temperature.Comment: 19 pages, 5 figure
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