744 research outputs found
Information gap for classical and quantum communication in a Schwarzschild spacetime
Communication between a free-falling observer and an observer hovering above
the Schwarzschild horizon of a black hole suffers from Unruh-Hawking noise,
which degrades communication channels. Ignoring time dilation, which affects
all channels equally, we show that for bosonic communication using single and
dual rail encoding the classical channel capacity reaches a finite value and
the quantum coherent information tends to zero. We conclude that classical
correlations still exist at infinite acceleration, whereas the quantum
coherence is fully removed.Comment: 5 pages, 4 figure
Characterization of Unruh Channel in the context of Open Quantum Systems
We show through the Choi matrix approach that the effect of Unruh
acceleration on a qubit is similar to the interaction of the qubit with a
vacuum bath, despite the finiteness of the Unruh temperature. Thus, rather
counterintuitvely, from the perspective of decoherence in this framework, the
particle experiences a vacuum bath with a temperature-modified interaction
strength, rather than a thermal bath. We investigate how this "relativistic
decoherence" is modified by the presence of environmentally induced
decoherence, by studying the degradation of quantum information, as quantified
by parameters such as nonlocality, teleportation fidelity, entanglement,
coherence and quantum measurement-induced disturbance (a discord-like measure).
Also studied are the performance parameters such as gate and channel fidelity.
We highlight the distinction between dephasing and dissipative environmental
interactions, by considering the actions of quantum non-demolition and squeezed
generalized amplitude damping channels, respectively, where, in particular,
squeezing is shown to be a useful quantum resource.Comment: 15 pages, 19 figure
Effect of relativistic acceleration on localized two-mode Gaussian quantum states
We study how an arbitrary Gaussian state of two localized wave packets,
prepared in an inertial frame of reference, is described by a pair of uniformly
accelerated observers. We explicitly compute the resulting state for
arbitrarily chosen proper accelerations of the observers and independently
tuned distance between them. To do so, we introduce a generalized Rindler frame
of reference and analytically derive the corresponding state transformation as
a Gaussian channel. Our approach provides several new insights into the
phenomenon of vacuum entanglement such as the highly non-trivial effect of
spatial separation between the observers including sudden death of
entanglement. We also calculate the fidelity of the two-mode channel for
non-vacuum Gaussian states and obtain bounds on classical and quantum
capacities of a single-mode channel. Our framework can be directly applied to
any continuous variable quantum information protocol in which the effects of
acceleration or gravity cannot be neglected.Comment: 21 pages, 13 figures. A few typos correcte
Quantum Communication in Rindler Spacetime
A state that an inertial observer in Minkowski space perceives to be the
vacuum will appear to an accelerating observer to be a thermal bath of
radiation. We study the impact of this Davies-Fulling-Unruh noise on
communication, particularly quantum communication from an inertial sender to an
accelerating observer and private communication between two inertial observers
in the presence of an accelerating eavesdropper. In both cases, we establish
compact, tractable formulas for the associated communication capacities
assuming encodings that allow a single excitation in one of a fixed number of
modes per use of the communications channel. Our contributions include a
rigorous presentation of the general theory of the private quantum capacity as
well as a detailed analysis of the structure of these channels, including their
group-theoretic properties and a proof that they are conjugate degradable.
Connections between the Unruh channel and optical amplifiers are also
discussed.Comment: v3: 44 pages, accepted in Communications in Mathematical Physic
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