116 research outputs found
Alice falls into a black hole: Entanglement in non-inertial frames
Two observers determine the entanglement between two free bosonic modes by
each detecting one of the modes and observing the correlations between their
measurements. We show that a state which is maximally entangled in an inertial
frame becomes less entangled if the observers are relatively accelerated. This
phenomenon, which is a consequence of the Unruh effect, shows that entanglement
is an observer-dependent quantity in non-inertial frames. In the high
acceleration limit, our results can be applied to a non-accelerated observer
falling into a black hole while the accelerated one barely escapes. If the
observer escapes with infinite acceleration, the state's distillable
entanglement vanishes.Comment: I.F-S published before with maiden name Fuentes-Guridi Replaced with
published version. Phys. Rev. Lett. in pres
Entanglement of Dirac fields in non-inertial frames
We analyze the entanglement between two modes of a free Dirac field as seen
by two relatively accelerated parties. The entanglement is degraded by the
Unruh effect and asymptotically reaches a non-vanishing minimum value in the
infinite acceleration limit. This means that the state always remains entangled
to a degree and can be used in quantum information tasks, such as
teleportation, between parties in relative uniform acceleration. We analyze our
results from the point of view afforded by the phenomenon of entanglement
sharing and in terms of recent results in the area of multi-qubit
complementarity.Comment: 15 pages, with 8 figures (Mar 2006); accepted to Physical Review A,
July 2006 - slightly revise
Degradation of non-maximal entanglement of scalar and Dirac fields in non-inertial frames
The entanglement between two modes of the free scalar and Dirac fields as
seen by two relatively accelerated observers has been investigated. It is found
that the same initial entanglement for an initial state parameter and
its "normalized partner" will be degraded by the Unruh
effect along two different trajectories except for the maximally entangled
state, which just shows the inequivalence of the quantization for a free field
in the Minkowski and Rindler coordinates. In the infinite acceleration limit
the state doesn't have the distillable entanglement for any for the
scalar field but always remains entangled to a degree which is dependent of
for the Dirac field. It is also interesting to note that in this limit
the mutual information equals to just half of the initially mutual information,
which is independent of and the type of field.Comment: 9 pages, 4 figure
Speeding up Entanglement Degradation
Entanglement between two free bosonic modes can be determined via detection
of each mode by different observers and then observing the correlations between
their measurements. We show that such entanglement is degraded as a function of
time if one observer begins in a state of inertial motion but ends in a state
of uniform acceleration while the other remains inertial. At late times we
recover previously established results for observers in relative uniform
acceleration.Comment: 5 pages, 2 figure
Bures distance between two displaced thermal states
The Bures distance between two displaced thermal states and the corresponding
geometric quantities (statistical metric, volume element, scalar curvature) are
computed. Under nonunitary (dissipative) dynamics, the statistical distance
shows the same general features previously reported in the literature by
Braunstein and Milburn for two--state systems. The scalar curvature turns out
to have new interesting properties when compared to the curvature associated
with squeezed thermal states.Comment: 3 pages, RevTeX, no figure
Hawking radiation, Entanglement and Teleportation in background of an asymptotically flat static black hole
The effect of the Hawking temperature on the entanglement and teleportation
for the scalar field in a most general, static and asymptotically flat black
hole with spherical symmetry has been investigated. It is shown that the same
"initial entanglement" for the state parameter and its "normalized
partners" will be degraded by the Hawking effect with
increasing Hawking temperature along two different trajectories except for the
maximally entangled state. In the infinite Hawking temperature limit,
corresponding to the case of the black hole evaporating completely, the state
has no longer distillable entanglement for any . It is interesting to
note that the mutual information in this limit equals to just half of the
"initially mutual information". It has also been demonstrated that the fidelity
of teleportation decreases as the Hawking temperature increases, which just
indicates the degradation of entanglement.Comment: 17 pages, 3 figures, to be published in Physical Review
The Rotating-Wave Approximation: Consistency and Applicability from an Open Quantum System Analysis
We provide an in-depth and thorough treatment of the validity of the
rotating-wave approximation (RWA) in an open quantum system. We find that when
it is introduced after tracing out the environment, all timescales of the open
system are correctly reproduced, but the details of the quantum state may not
be. The RWA made before the trace is more problematic: it results in incorrect
values for environmentally-induced shifts to system frequencies, and the
resulting theory has no Markovian limit. We point out that great care must be
taken when coupling two open systems together under the RWA. Though the RWA can
yield a master equation of Lindblad form similar to what one might get in the
Markovian limit with white noise, the master equation for the two coupled
systems is not a simple combination of the master equation for each system, as
is possible in the Markovian limit. Such a naive combination yields inaccurate
dynamics. To obtain the correct master equation for the composite system a
proper consideration of the non-Markovian dynamics is required.Comment: 17 pages, 0 figures
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