Observing Parity Time Symmetry Breaking in a Josephson Parametric Amplifier

TL;DR

This paper demonstrates the observation of parity-time symmetry breaking in a Josephson parametric amplifier by using a two-mode system with balanced gain and loss, revealing a transition in the system's eigenvalues.

Contribution

It introduces a novel experimental realization of PT-symmetry breaking in a superconducting quantum device using a degenerate parametric amplifier.

Findings

Observation of real-to-imaginary eigenvalue transition

Identification of PT-symmetry-breaking transition in a quantum amplifier

Experimental evidence of parity-time symmetry phenomena

Abstract

A coupled two-mode system with balanced gain and loss is a paradigmatic example of an open quantum system that can exhibit real spectra despite being described by a non-Hermitian Hamiltonian. We utilize a degenerate parametric amplifier operating in three-wave mixing mode to realize such a system of balanced gain and loss between the two quadrature modes of the amplifier. By examining the time-domain response of the amplifier, we observe a characteristic transition from real-to-imaginary energy eigenvalues associated with the Parity-Time-symmetry-breaking transition.