Observing Parity Time Symmetry Breaking in a Josephson Parametric Amplifier

Parity-Time (PT) symmetry, first devised as a theoretical concept and later realized in optics has quickly grown to become a major field with significant applications. The simplest realization of such systems is a PT dimer with two modes exhibiting gain and loss respectively. The important phenomena that make these systems interesting are PT symmetry broken and unbroken regions separated by an exceptional point degeneracy. PT-symmetric Hamiltonians may be realized by engineering controlled interactions with an environment of a quantum system but there are multiple other ways to design such an arrangement. In this work, we design a narrowband JPA working in a three-wave mixing mode to observe PT symmetry-broken and unbroken regions in the transient response. Here the two quadratures are two modes of the PT dimer. The non-Hermitian nature of the equations of motion of the cavity modes gives insight into the functionality of a Josephson parametric amplifier and sets the stage for harnessing the physics of exceptional points in large arrays of such parametric devices.