Conditions for strictly purity-decreasing quantum Markovian dynamics
نویسندگان
چکیده
The purity, Tr(q), measures how pure or mixed a quantum state q is. It is well known that quantum dynamical semigroups that preserve the identity operator (which we refer to as unital) are strictly purity-decreasing transformations. Here, we provide an almost complete characterization of the class of strictly purity-decreasing quantum dynamical semigroups. We show that in the case of finite-dimensional Hilbert spaces, a dynamical semigroup is strictly purity-decreasing if and only if it is unital, while in the infinite dimensional case, unitality is only sufficient. 2005 Elsevier B.V. All rights reserved.
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