From projected to observable-projected ensembles

          @misc{ scivideos_oai:cds.cern.ch:3025659,
            doi = {},
            url = {https://videos.cern.ch/record/3025659},
            author = {},
            keywords = {},
            language = {en},
            title = {From projected to observable-projected ensembles},
            publisher = {},
            year = {2026},
            month = {may},
            note = {oai:cds.cern.ch:3025659 see, \url{https://scivideos.org/cern-cds/3025659}}
          }
          

Abstract

Local measurements offer a powerful way to probe novel quantum phenomena, thermalization, and universal distributions in many-body quantum systems. In this talk, I will introduce the observable-projected ensemble, in which the subsystem state is conditioned on the outcome of measuring a single local Hermitian operator on part of its complement, rather than on a complete projective measurement of the whole complement. This protocol avoids the exponential complexity of conventional projected ensembles while remaining analytically tractable. I will discuss how its k-th moments compare with those of the Haar ensemble and show that, rather than approaching the Haar ensemble, the observable-projected ensemble can become exponentially distinguishable from it as the bath size grows. I will also describe its field-theoretic formulation in critical systems and illustrate the construction with the free compact boson.

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