Quantum mechanics

Quantum decoherence

Phase transition

Criticality

Nuclear physics

Critical point (mathematics)

Statistical physics

Physics

Quantum entanglement

Mathematics

Fermion

Mathematical analysis

Quantum

Quantum discord

Quantum Zeno effect

Quantum phase transition

Critical phenomena

Quantum critical point

Physical Review Letters

We analyze the quantum trajectory dynamics of free fermions subject to continuous monitoring. For weak monitoring, we identify a novel dynamical regime of subextensive entanglement growth, reminiscent of a critical phase with an emergent conformal invariance. For strong monitoring, however, the dynamics favors a transition into a quantum Zeno-like area-law regime. Close to the critical point, we observe logarithmic finite size corrections, indicating a Berezinskii-Kosterlitz-Thouless mechanism underlying the transition. This uncovers an unconventional entanglement transition in an elementary, physically realistic model for weak continuous measurements. In addition, we demonstrate that the measurement aspect in the dynamics is crucial for whether or not a phase transition takes place.

Entanglement Transition in a Monitored Free-Fermion Chain: From Extended Criticality to Area Law