286 research outputs found
Quantum Phase Transitions in a Linear Ion Trap
We show that the quantum phase transition of the Tavis-Cummings model can be
realised in a linear ion trap of the kind proposed for quantum computation. The
Tavis-Cummings model describes the interaction between a bosonic degree of
freedom and a collective spin. In an ion trap, the collective spin system is a
symmetrised state of the internal electronic states of N ions, while the
bosonic system is the vibrational degree of freedom of the centre of mass mode
for the ions.Comment: 6 pages and 2 figures. submitted to Dan Walls Memorial Volume, edited
by H. Carmichael, R. Glauber, and M. Scully, to be published by Springe
Entanglement of two qubits in a relativistic orbit
The creation and destruction of entanglement between a pair of interacting
two-level detectors accelerating about diametrically opposite points of a
circular path is investigated. It is found that any non-zero acceleration has
the effect of suppressing the vacuum entanglement and enhancing the
acceleration radiation thereby reducing the entangling capacity of the
detectors. Given that for large accelerations the acceleration radiation is the
dominant effect, we investigate the evolution of a two detector system
initially prepared in a Bell state using a perturbative mater equation and
treating the vacuum fluctuations as an unobserved environment. A general
function for the concurrence is obtained for stationary and symmetric
worldlines in flatspace. The entanglement sudden death time is computed.Comment: v2: Some typo's fixed, figures compressed to smaller filesize and
added some references
Teleportation with a uniformly accelerated partner
In this work, we give a description of the process of teleportation between
Alice in an inertial frame, and Rob who is in uniform acceleration with respect
to Alice. The fidelity of the teleportation is reduced due to Unruh radiation
in Rob's frame. In so far as teleportation is a measure of entanglement, our
results suggest that quantum entanglement is degraded in non inertial frames.Comment: 7 pages with 4 figures (in revtex4
Matter waves in a gravitational field: An index of refraction for massive particles in general relativity
We consider the propagation of massive-particle de Broglie waves in a static,
isotropic metric in general relativity. We demonstrate the existence of an
index of refraction that governs the waves and that has all the properties of a
classical index of refraction. We confirm our interpretation with a WKB
solution of the general-relativistic Klein-Gordon equation. Finally, we make
some observations on the significance of the optical action.Comment: 20 pages, latex, ps and pdf. To appear in Am.J.Phys September, 200
Quantum Entanglement and Teleportation in Higher Dimensional Black Hole Spacetimes
We study the properties of quantum entanglement and teleportation in the
background of stationary and rotating curved space-times with extra dimensions.
We show that a maximally entangled Bell state in an inertial frame becomes less
entangled in curved space due to the well-known Hawking-Unruh effect. The
degree of entanglement is found to be degraded with increasing the extra
dimensions. For a finite black hole surface gravity, the observer may choose
higher frequency mode to keep high level entanglement. The fidelity of quantum
teleporation is also reduced because of the Hawking-Unruh effect. We discuss
the fidelity as a function of extra dimensions, mode frequency, black hole mass
and black hole angular momentum parameter for both bosonic and fermionic
resources.Comment: 15 pages, 10 figures,contents expande
Squeezing enhancement by damping in a driven atom-cavity system
In a driven atom-cavity coupled system in which the two-level atom is driven
by a classical field, the cavity mode which should be in a coherent state in
the absence of its reservoir, can be squeezed by coupling to its reservoir. The
squeezing effect is enhanced as the damping rate of the cavity is increased to
some extent.Comment: 3 pages and 3 figure
- …