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Phys. Rev. A 67, 062312 (2003) [13 pages]

Quantum Markov channels for qubits

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Sonja Daffer1, Krzysztof Wódkiewicz1,2, and John K. McIver1
1Department of Physics and Astronomy, University of New Mexico, 800 Yale Boulevard NE, Albuquerque, New Mexico 87131, USA
2Instytut Fizyki Teoretycznej, Uniwersytet Warszawski, Hoża 69, Warszawa 00-681, Poland

Received 31 October 2002; published 26 June 2003

We examine stochastic maps in the context of quantum optics. Making use of the master equation, the damping basis, and the Bloch picture we calculate a nonunital, completely positive, trace-preserving map with unequal damping eigenvalues. This results in what we call the squeezed vacuum channel. A geometrical picture of the effect of stochastic noise on the set of pure state qubit density operators is provided. Finally, we study the capacity of the squeezed vacuum channel to transmit quantum information and to distribute Einstein-Podolsky-Rosen states.


©2003 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevA.67.062312
DOI: 10.1103/PhysRevA.67.062312
PACS: 03.67.Hk, 42.50.Lc, 03.65.Yz

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