299 research outputs found
Quantum Information Transmission over a Partially Degradable Channel
We investigate a quantum coding for quantum communication over a PD
(partially degradable) degradable quantum channel. For a PD channel, the
degraded environment state can be expressed from the channel output state up to
a degrading map. PD channels can be restricted to the set of optical channels
which allows for the parties to exploit the benefits in experimental quantum
communications. We show that for a PD channel, the partial degradability
property leads to higher quantum data rates in comparison to those of a
degradable channel. The PD property is particular convenient for quantum
communications and allows one to implement the experimental quantum protocols
with higher performance. We define a coding scheme for PD-channels and give the
achievable rates of quantum communication.Comment: 7 pages, 2 figures, Journal-ref: IEEE Acces
Quantum information transmission through a qubit chain with quasi-local dissipation
We study quantum information transmission in a Heisenberg-XY chain where
qubits are affected by quasi-local environment action and compare it with the
case of local action of the environment. We find that for open boundary
conditions the former situation always improves quantum state transfer process,
especially for short chains. In contrast, for closed boundary conditions
quasi-local environment results advantageous in the strong noise regime. When
the noise strength is comparable with the XY interaction strength, the state
transfer fidelity through chain of odd/even number of qubits in presence of
quasi-local environment results smaller/greater than that in presence of local
environment
Aspects of multistation quantum information broadcasting
We study quantum information transmission over multiparty quantum channel. In
particular, we show an equivalence of different capacity notions and provide a
multiletter characterization of a capacity region for a general quantum channel
with senders and receivers. We point out natural generalizations to the
case of two-way classical communication capacity.Comment: New title, major changes, extended, journal ref. adde
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
Quantum state transfer via the ferromagnetic chain in a spatially modulated field
We show that a perfect quantum state transmission can be realized through a
spin chain possessing a commensurate structure of energy spectrum, which is
matched with the corresponding parity. As an exposition of the mirror inversion
symmetry discovered by Albanese et. al (quant-ph/0405029), the parity matched
the commensurability of energy spectra help us to present the novel
pre-engineered spin systems for quantum information transmission. Based on the
these theoretical analysis, we propose a protocol of near-perfect quantum state
transfer by using a ferromagnetic Heisenberg chain with uniform coupling
constant, but an external parabolic magnetic field. The numerical results shows
that the initial Gaussian wave packet in this system with optimal field
distribution can be reshaped near-perfectly over a longer distance.Comment: 5 pages, 2 figure
Structured light, transmission, and scattering
Numerous theoretical and experimental studies have established the principle that beams conveying orbital angular momentum offer a rich scope for information transfer. However, it is not clear how far it is practicable to operate such a concept at the single-photon level - especially when such a beam propagates through a system in which scattering can occur. In cases where scattering leads to photon deflection, it produces losses; however in terms of the retention of information content, there should be more concern over forward scattering. Based on a quantum electrodynamical formulation of theory, this paper aims to frame and resolve the key issues. A quantum amplitude is constructed for the representation of single and multiple scattering events in the propagation an individual photon, from a suitably structured beam. The analysis identifies potential limitations of principle, undermining complete fidelity of quantum information transmission
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