Absorption and Fixed Points for Semigroups of Quantum Channels

DOI10.1007/978-3-031-06170-7_10arXiv2204.12987MaRDI QIDQ6397620

Publication date: 27 April 2022

Abstract: In the present work we review and refine some results about fixed points of semigroups of quantum channels. Noncommutative potential theory enables us to show that the set of fixed points of a recurrent semigroup is a W*-algebra; aside from the intrinsic interest of this result, it brings an improvement in the study of fixed points by means of absorption operators (a noncommutative generalization of absorption probabilities): under the assumption of absorbing recurrent space (hence allowing non-trivial transient space) we can provide a description of the fixed points set and a probabilistic characterization of when it is a W*-algebra in terms of absorption operators. Moreover we are able to exhibit an example of a recurrent semigroup which does not admit a decomposition of the Hilbert space into orthogonal minimal invariant domains (contrarily to the case of classical Markov chains and positive recurrent semigroups of quantum channels).

Mathematics Subject Classification ID

Markov semigroups and applications to diffusion processes (47D07) Iteration of holomorphic maps, fixed points of holomorphic maps and related problems for several complex variables (32H50) Applications of Brownian motions and diffusion theory (population genetics, absorption problems, etc.) (60J70) Other degrees and reducibilities in computability and recursion theory (03D30) Notions of recurrence and recurrent behavior in topological dynamical systems (37B20) Quantum channels, fidelity (81P47)

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