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

TL;DR

This paper demonstrates measurement-induced quantum phase transitions in a trapped-ion quantum computer by implementing random circuits with measurements, revealing phases of pure and mixed states and their critical properties.

Contribution

It provides experimental evidence of measurement-induced phase transitions in a trapped-ion system, highlighting the interplay between unitary dynamics and measurements in quantum many-body systems.

Findings

Evidence of two distinct quantum phases: pure and mixed.

Observation of a critical point with emerging phase transition properties.

Numerical analysis showing clear critical behavior with modest system scaling.

Abstract

Many-body open quantum systems balance internal dynamics against decoherence from interactions with an environment. Here, we explore 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-tolerent threshold. 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 convincing evidence of the two phases and show numerically that, with modest system scaling, critical properties of the transition clearly emerge.