Dissipative microcanonical ensemble preparation from KMS-detailed balance

TL;DR

This paper explores methods to prepare stationary quantum states, including microcanonical ensembles, using KMS-detailed balance, with implications for efficient state preparation and testing ensemble equivalences.

Contribution

It extends KMS-detailed balance constructions to stationary state preparation, providing criteria for efficient implementation and microcanonical ensemble approximation.

Findings

Extended KMS-detailed balance to stationary states.

Provided criteria for efficient state preparation.

Tested ensemble equivalences for local observables.

Abstract

Stationary states of quantum many-body Hamiltonians are invariant under the Hamiltonian evolution. Besides ground and thermal states, this class includes microcanonical ensembles that are of fundamental importance in statistical physics. We consider the preparation of general stationary states by leveraging recent advances in the field of open-system dynamics. In particular, constructions based on exact KMS-detailed balance with respect to Gibbs states of noncommuting Hamiltonians have only recently been proposed as a tool for their efficient preparation and, by extension to small temperatures, for ground state preparation. We extend these constructions to the problem of stationary state preparation, providing general criteria that characterize when such states have efficient implementations, along with specific results on the approximation of microcanonical ensembles. An interesting application of our work are tests of conjectured ensemble equivalences for local observables between microcanonical and Gibbs ensembles.