Qubit Vitrification and Entanglement Criticality on a Quantum Simulator

TL;DR

This paper demonstrates that sequential measurements on a quantum simulator can induce a phase transition in entanglement, revealing critical phenomena akin to spin glass behavior and vitrification.

Contribution

It introduces the concept of measurement-induced entanglement criticality and experimentally determines the vitrification point in a 48-qubit system.

Findings

Measurements can trigger entanglement phase transitions.

Vitrification point and critical exponent match spin glass theory.

Entanglement criticality can be driven by coupling to a classical environment.

Abstract

Many elusive quantum phenomena emerge from the interaction of a quantum system with its classical environment. Quantum simulators enable us to program this interaction by using measurement operations. Measurements generally remove part of the quantum entanglement built between the qubits inside a simulator. While in simple cases entanglement may disappear at a constant rate as we measure qubits one by one, the evolution of entanglement under measurements for a given class of quantum states is generally unknown. Here, we show that consecutive measurements of the qubits in a quantum simulator can lead to criticality, separating two phases of entanglement. We prepare an entangled superposition of ground states to a classical spin model and show that progressively measuring the qubits drives the simulator into a spin glass phase of entanglement. By entangling and measuring up to 48 qubits in this fashion, we determine the vitrification point and its critical exponent, which obey spin glass theory exactly. Our findings show that measurements alone can trigger entanglement criticality and suggest that coupling to a classical environment can drive critical phenomena in more general quantum states.