Circuit-based characterization of finite-temperature quantum phases

          @misc{ scivideos_PIRSA:26050022,
            doi = {10.48660/26050022},
            url = {https://pirsa.org/26050022},
            author = {Sang, Shengqi},
            keywords = {Quantum Information, Quantum Matter},
            language = {en},
            title = {Circuit-based characterization of finite-temperature quantum phases},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2026},
            month = {may},
            note = {PIRSA:26050022 see, \url{https://scivideos.org/pirsa/26050022}}
          }
          

Abstract

Quantum phases at zero temperature can be defined as equivalence classes under local unitary transformations: two ground states are in the same phase if they can be transformed into each other via a local unitary circuit. In this talk, I will discuss how to generalize this circuit-based characterization of phases to systems at finite-temperature described by Gibbs states. We construct a local quantum channel circuit that approximately transforms one Gibbs state into another provided the two are connected by a path in parameter space along which a certain correlation-decay condition holds. This correlation-decay condition is expected to be satisfied in the interior of many noncritical thermal phases. As an application, I will show that any system in the same thermal phase as a zero-temperature topological code coherently preserves quantum information for a macroscopically long time, establishing self-correction as a universal property of thermal phases.