Cavity QED as a Platform for Simulating Dynamical Phases of Quenched Superconductors*

While equilibrium properties of physical systems are well described by statistical mechanics, out-of-equilibrium interacting systems exhibit rich phenomenology that is hard to capture with tools from equilibrium settings.  Bardeen–Cooper–Schrieffer (BCS) theory is a tremendously successful theory in describing Type I superconductors, accurately modeling various superconductor properties, like the gap and critical temperature. However, experimental verification of long predicted dynamical phases for quenched superconductors remains elusive [1]. In this work, we experimentally demonstrate all three dynamical phases predicted for a quenched BCS superconductor using a strontium (88-Sr) cavity-QED system. We explore the dynamics of the superconducting gap by engineering the dispersion relation and the strength of interaction in the BCS Hamiltonian. We demonstrate how these dynamical phases are universal in different implementations of the Hamiltonian. We also show how this physics can be thought of as a form of gap protection for coherence for applications in quantum sensing and metrology.

[1] R. A. Barankov and L. S. Levitov, PRL 96, 230403 (2006)