Characterizing Many-body Dynamics with Projected Ensembles on a Superconducting Quantum Processor

Abstract: Quantum simulators offer a new opportunity for the experimental exploration of non-equilibrium quantum many-body dynamics, which have traditionally been characterized through expectation values or entanglement measures, based on density matrices of the system. Recently, a more general framework for studying quantum many-body systems based on projected ensembles has been introduced, revealing novel quantum phenomena, such as deep thermalization in chaotic systems. Here, we experimentally investigate a chaotic quantum many-body system using projected ensembles on a superconducting processor with 16 qubits on a square lattice. Our results provide direct evidence of deep thermalization by observing a Haar-distributed projected ensemble for the steady states within a charge-conserved sector. Moreover, by introducing an ensemble-averaged entropy as a metric, we establish a benchmark for many-body information leakage from the system to its environment. Our work paves the way for studying quantum many-body dynamics using projected ensembles and shows a potential implication for advancing quantum simulation techniques.