Article
Measurement-Induced Phases of Matter Require Feedback Public Deposited
- Abstract
We explore universality and phases of matter in hybrid quantum dynamics combining chaotic time evolution and projective measurements. We develop a unitary representation of measurements based on the Stinespring theorem, which we crucially identify with the time evolution of the system and measurement apparatus, affording significant technical advantages and conceptual insight into hybrid dynamics. We diagnose spectral properties in the presence of measurements for the first time, along with standard, experimentally tractable probes of phase structure, finding no nontrivial effects due to measurements in the absence of feedback. We also establish that nonlinearity in the density matrix is neither sufficient nor necessary to see a transition, and instead identify utilization of the measurement outcomes (i.e., “feedback”) as the crucial ingredient. After reviewing the definition of a phase of matter, we identify nontrivial orders in adaptive hybrid dynamics—in which measurement outcomes determine future unitary gates—finding a genuine measurement-induced absorbing-state phase transition in an adaptive quantum East model. In general, we find that only deterministic and constrained Haar-random dynamics with active feedback and without continuous symmetries can realize genuine, measurement-induced phases of matter.
- Creator
- Date Issued
- 2023
- Additional Information
- Publication of this article was funded by the University of Colorado Boulder Libraries Open Access Fund.
- Academic Affiliation
- Journal Title
- Journal Issue/Number
- 4
- Journal Volume
- 4
- Last Modified
- 2023-10-13
- Resource Type
- Rights Statement
- DOI
- ISSN
- 2691-3399
- Language
- License
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PRXQuantum.4.040309.pdf | 2023-10-13 | Public | Download |