Measurement-induced phase transition in free bosons

TL;DR

This paper investigates measurement-induced phase transitions in free bosonic systems with long-range couplings, revealing that nonlocal measurements can induce a phase transition characterized by a subvolume-to-area law change in entanglement entropy.

Contribution

It demonstrates the occurrence of MIPTs in free bosons with long-range couplings under nonlocal measurements, a phenomenon not observed with local measurements.

Findings

Local measurements do not induce MIPTs in free bosons.

Nonlocal measurements can induce a MIPT with a subvolume-to-area law transition.

The critical point is likely described by a conformal field theory, distinct from conventional universality classes.

Abstract

The competition between quantum many-particle dynamics and continuous monitoring can lead to measurement-induced phase transitions (MIPTs). So far, MIPTs have been extensively explored in fermionic or spin systems. To examine the possibility of an MIPT in bosonic systems, we study the entanglement structure in continuously monitored free bosons with long-range couplings. When the measurement is local, we find that no MIPTs occur because the substantial entanglement generated by the long-range coupling overcomes the entanglement destruction due to the measurement. In contrast, we show that the nonlocal measurement can efficiently suppress the entanglement generation, leading to an MIPT where the bipartite entanglement entropy exhibits the subvolume-to-area law phase transition as the measurement strength is increased. Our numerical results indicate that the critical point should be described by a certain conformal field theory, while the transition does not belong to a conventional universality class such as Berezinskii-Kosterlitz-Thouless class.