Inverse Superconductor-Insulator Transition in Weakly Monitored Josephson Junction Arrays

Control and manipulation of quantum states by measurements and bath engineering in open quantum systems, like in a quantum computer, have emerged as new paradigms in many-body physics. Taking a prototypical example of Josephson junction arrays (JJAs), we show how monitoring through continuous weak measurements and feedback can transform an insulating state in JJAs to a superconductor and vice versa. We show that, even in the absence of any external thermal bath, the monitoring leads to an effective temperature for the long-time steady state in a semiclassical limit. However, we show that the quantum dissipation due to monitoring has fundamental differences with equilibrium quantum and/or thermal dissipation in the well-studied case of JJAs in contact with an Ohmic bath. Thus, in general, a description in terms of only an effective temperature is not adequate for the monitored JJAs. Using a variational approximation, and by considering various limiting cases, we demonstrate that this difference can give rise to unusual inverse transition from an effective low-temperature insulating normal state to a superconducting state at intermediate temperature.