Observation of measurement-induced quantum phases in a trapped-ion quantum computer

Many-body open quantum systems balance internal dynamics against decoherence from interactions with an environment. In this talk, I describe an experiment that explores this balance via random quantum circuits implemented on a trapped-ion quantum computer, where the system evolution is represented by unitary gates with interspersed projective measurements. As the measurement rate is varied, a purification phase transition is predicted to emerge at a critical point akin to a fault-tolerant threshold. In the experiment, we probe the "pure'' phase, where the system is rapidly projected to a deterministic state conditioned on the measurement outcomes, and the "mixed'' or "coding'' phase, where the initial state becomes partially encoded into a quantum error correcting codespace. We find evidence of the two phases and show numerically that, with modest system scaling, critical properties of the transition emerge.

Pizza and drinks served after the talk.