Finding the Kraus decomposition from a master equation and vice versa
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For any master equation which is local in time, whether Markovian, non-Markovian, of Lindblad form or not, a general procedure is given for constructing the corresponding linear map from the initial state to the state at time t, including its Kraus-type representations. Formally, this is equivalent to solving the master equation. For an N-dimensional Hilbert space it requires (i) solving a first order N 2 2 matrix time evolution (to obtain the completely positive map), and (ii) diagonalizing a related N 2 2 matrix (to obtain a Kraus-type representation). Conversely, for a given time-dependent linear map, a necessary and sufficient condition is given for the existence of a corresponding master equation, where the (not necessarily unique) form of this equation is explicitly determined. It is shown that a "best possible" master equation may always be defined, for approximating the evolution in the case that no exact master equation exists. Examples involving qubits are given.
Journal of Modern Optics
© 2007 Taylor & Francis. This is an electronic version of an article published in Journal of Modern Optics, Vol.54(12), 2007, pp.1695-1716. Journal of Modern Optics is available online at: http://www.tandfonline.com with the open URL of your article.
Mathematical Aspects of Classical Mechanics, Quantum Mechanics and Quantum Information Theory
Quantum Physics not elsewhere classified