Zack Weinstein
In quantum circuits consisting of random unitary evolution interspersed with random measurements, a volume-law to area-law phase transition in the averaged pure state entanglement entropy is known to occur at a critical measurement rate. As a first step towards understanding similar phase transitions in open quantum systems with more realistic decoherent processes, we study the entanglement dynamics of two weakly coupled qubit chains, where one chain can be viewed as an effective bath for the other. We find a second order volume-law to area-law transition in the logarithmic entanglement negativity, a robust measure of mixed state entanglement, between the two halves of the "system chain". No corresponding transition is observed in the entanglement entropy for any bi-partition of the two chain ladder, which always remains in a volume-law phase. We present numerical evidence of this transition in classically simulable Clifford circuits, and discuss a possible analytical understanding of the transition using an effective statistical mechanics model.