# Scalable Probes of Measurement-Induced Criticality

## Author(s): Gullans, Michael J; Huse, David A

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 Abstract: We uncover a local order parameter for measurement-induced phase transitions: the average entropy of a single reference qubit initially entangled with the system. Using this order parameter, we identify scalable probes of measurement-induced criticality that are immediately applicable to advanced quantum computing platforms. We test our proposal on a 1 + 1 dimensional stabilizer circuit model that can be classically simulated in polynomial time. We introduce the concept of a “decoding light cone” to establish the local and efficiently measurable nature of this probe. We also estimate bulk and surface critical exponents for the transition. Developing scalable probes of measurement-induced criticality in more general models may be a useful application of noisy intermediate scale quantum devices, as well as point to more efficient realizations of fault-tolerant quantum computation. Publication Date: 14-Aug-2020 Electronic Publication Date: 14-Aug-2020 Citation: Gullans, Michael J, Huse, David A. (2020). Scalable Probes of Measurement-Induced Criticality. PHYSICAL REVIEW LETTERS, 125 (10.1103/PhysRevLett.125.070606 DOI: doi:10.1103/PhysRevLett.125.070606 ISSN: 0031-9007 EISSN: 1079-7114 Type of Material: Journal Article Journal/Proceeding Title: PHYSICAL REVIEW LETTERS Version: Final published version. Article is made available in OAR by the publisher's permission or policy.