Work

Diagnosing Chaos with Projected Ensembles of Process Tensors

Year: 2026

Type: article

Abstract: The process tensor provides a general representation of a quantum system evolving under repeated interventions and is fundamental for numerical simulations of local many-body dynamics. In this work, we introduce the projected process ensemble, an ensemble of pure output states of a process tensor in a given basis of local interventions, and use it to define increasingly more fine-grained probes of quantum chaos. The first moment of this ensemble encapsulates numerous previously studied chaos quantifiers, including the Alicki-Fannes quantum dynamical entropy, butterfly flutter fidelity, and spatiotemporal entanglement. We discover characteristic entanglement structures within the ensemble’s higher moments that can sharply distinguish chaotic from integrable dynamics, overcoming deficiencies of the quantum dynamical and spatiotemporal entropies. These conclusions are supported by extensive numerical simulations of many-body dynamics for a range of spin-chain models, including noninteracting, interacting-integrable, chaotic, and many-body localized regimes. Our work elucidates the fingerprints of chaos on spatiotemporal correlations in quantum stochastic processes and provides a unified framework for analyzing the complexity of unitary and monitored many-body dynamics.

Source: PRX Quantum

DOI: 10.1103/fgc4-hgk1

Authors: Peter O’Donovan, Neil Dowling, Kavan Modi, Mark T. Mitchison

Institutions: Trinity College Dublin, University of Cologne, Monash University, Singapore University of Technology and Design, King's College London

Language: English

Topic: Quantum many-body systems

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,450

Funders: Australian Government, Deutsche Forschungsgemeinschaft, Irish Research Council, Irish Centre for High-End Computing