arXiv:2510.26895 · Quantum Science and Technology

Exact and approximate conditions of tabletop reversibility: when is Petz recovery cost-free?

Minjeong Song, Hyukjoon Kwon, Valerio Scarani

Published Sep 17, 2026• 0 citations

Abstract

Abstract Channels N that describe open quantum dynamics are inherently irreversible: it is impossible to undo their effect completely, but one can study partial recovery of the information. The Petz recovery map N ^ γ ( P ) is a systematic construction that depends only on N and on a reference state γ , which will be recovered exactly. If the real input state was different from γ , the recovery is partial, with a guarantee of near-optimality. Generically, an implementation of the Petz recovery map would look very different from the implementation of the channel. It is natural to study under which conditions the two maps require similar or even identical resources. The noisy forward channel N is called tabletop time-reversible (TTR) for a given γ when the corresponding Petz recovery map is realizable in such a way. First, we study the exact TTR conditions. We show in particular that a time-sensitive control of an ancilla system is needed for the exact TTR. Second, we present the approximate TTR conditions, which do not require such a time-sensitive control. Third, we derive Lindbladian TTR conditions under a random-time collision model, and demonstrate it with an excitation-exchange Hamiltonian.

DOI: 10.1088/2058-9565/aea92d

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