Entanglement Phase Transitions in Measurement-Only Dynamics

Unitary circuits subject to repeated projective measurements can undergo an entanglement phase transition (EPT) as a function of the measurement rate. This is generally understood in terms competition between scrambling effects unitary dynamics and disentangling measurements. We find that, surprisingly, EPTs are possible even absence dynamics, where they best arising from alone. motivates us introduce \emph{measurement-only models}, which "scrambling" "un-scrambling" driving EPT fundamentally intertwined cannot be attributed physically distinct processes. represents novel form EPT, conceptually that hybrid unitary-projective circuits. explore diagrams, critical points, quantum code properties some these measurement-only models. principle models \emph{frustration}, or mutual incompatibility, Suprisingly, entangling (volume-law) generic outcome when measuring sufficiently long but still local ($\gtrsim 3$-body) operators. identify class exceptions this behavior ("bipartite ensembles") sustain phase, display dual area-law phases, possibly with different kinds order, separated by self-dual points. Finally, we measure information spreading use it demonstrate emergence statistical light-cone, despite non-locality inherent