Quantum Processor Shares Mixed Phase Space Without Classical Analog

A superconducting quantum processor has revealed a quantum many-body mixed phase space, a surprising discovery because this behavior lacks a direct analogue in classical or few-body quantum systems. Researchers led by Hang Dong and a team of 11 authors developed a hybrid quantum-classical feedback protocol to autonomously discover and stabilize long-lived regular trajectories within the processor. This protocol combines short bursts of quantum evolution with classical optimization, effectively distilling coherence from chaotic behavior by projecting dynamics onto a low-entanglement variational manifold. The stabilized trajectories reveal a mixed phase space, establishing a framework for controlling previously inaccessible coherent dynamics; this work addresses a central challenge of nonequilibrium physics, understanding the transition between order and chaos in complex systems.

This innovative approach unveiled the mixed phase space itself and demonstrates that nonlinear variational dynamics can generate complex quantum states previously inaccessible to experimental observation, offering a new avenue for studying the transition from order to chaos.

The findings, detailed in a recent paper, establish a versatile framework for algorithmic discovery and control of coherent dynamics, potentially reshaping how scientists approach complex quantum systems and their inherent unpredictability.