22,382 research outputs found
Perturbational approach to the quantum capacity of additive Gaussian quantum channel
For a quantum channel with additive Gaussian quantum noise, at the large
input energy side, we prove that the one shot capacity is achieved by the
thermal noise state for all Gaussian state inputs, it is also true for
non-Gaussian input in the sense of first order perturbation. For a general case
of copies input, we show that up to first order perturbation, any
non-Gaussian perturbation to the product thermal state input has a less quantum
information transmission rate when the input energy tend to infinitive.Comment: 5 page
Dependence of the decoherence of polarization states in phase-damping channels on the frequency spectrum envelope of photons
We consider the decoherence of photons suffering in phase-damping channels.
By exploring the evolutions of single-photon polarization states and two-photon
polarization-entangled states, we find that different frequency spectrum
envelopes of photons induce different decoherence processes. A white frequency
spectrum can lead the decoherence to an ideal Markovian process. Some color
frequency spectrums can induce asymptotical decoherence, while, some other
color frequency spectrums can make coherence vanish periodically with variable
revival amplitudes. These behaviors result from the non-Markovian effects on
the decoherence process, which may give rise to a revival of coherence after
complete decoherence.Comment: 7 pages, 4 figures, new results added, replaced by accepted versio
Perturbation theory of von Neumann Entropy
In quantum information theory, von Neumann entropy plays an important role.
The entropies can be obtained analytically only for a few states. In continuous
variable system, even evaluating entropy numerically is not an easy task since
the dimension is infinite. We develop the perturbation theory systematically
for calculating von Neumann entropy of non-degenerate systems as well as
degenerate systems. The result turns out to be a practical way of the expansion
calculation of von Neumann entropy.Comment: 7 page
Domain Wall Brane in Eddington Inspired Born-Infeld Gravity
Recently, inspired by Eddington's theory, an alternative gravity called
Eddington-inspired Born-Infeld gravity was proposed by Baados
and Ferreira. It is equivalent to Einstein's general relativity in vacuum, but
deviates from it when matter is included. Interestingly, it seems that the
cosmological singularities are prevented in this theory. Based on the new
theory, we investigate a thick brane model with a scalar field presenting in
the five-dimensional background. A domain wall solution is obtained, and
further, we find that at low energy the four-dimensional Einstein gravity is
recovered on the brane. Moreover, the stability of gravitational perturbations
is ensured in this model.Comment: 16 pages, 2 figures, improved versio
Relationship between High-Energy Absorption Cross Section and Strong Gravitational Lensing for Black Hole
In this paper, we obtain a relation between the high-energy absorption cross
section and the strong gravitational lensing for a static and spherically
symmetric black hole. It provides us a possible way to measure the high-energy
absorption cross section for a black hole from strong gravitational lensing
through astronomical observation. More importantly, it allows us to compute the
total energy emission rate for high-energy particles emitted from the black
hole acting as a gravitational lens. It could tell us the range of the
frequency, among which the black hole emits the most of its energy and the
gravitational waves are most likely to be observed. We also apply it to the
Janis-Newman-Winicour solution. The results suggest that we can test the cosmic
censorship hypothesis through the observation of gravitational lensing by the
weakly naked singularities acting as gravitational lenses.Comment: 6 pages, 2 figures, improved version, accepted for publication as a
Rapid Communication in Physical Review
Topological quantum phase transition in an extended Kitaev spin model
We study the quantum phase transition between Abelian and non-Abelian phases
in an extended Kitaev spin model on the honeycomb lattice, where the periodic
boundary condition is applied by placing the lattice on a torus. Our analytical
results show that this spin model exhibits a continuous quantum phase
transition. Also, we reveal the relationship between bipartite entanglement and
the ground-state energy. Our approach directly shows that both the entanglement
and the ground-state energy can be used to characterize the topological quantum
phase transition in the extended Kitaev spin model.Comment: 9 Pages, 4 figure
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