Decoherence Induced Exceptional Points in a Dissipative Superconducting Qubit

TL;DR

This paper demonstrates the observation of Liouvillian exceptional points in a superconducting qubit system, revealing new dynamics due to dissipation and decoherence, and enabling controlled state transfer via non-Hermitian effects.

Contribution

It experimentally identifies two types of Liouvillian exceptional points in a superconducting circuit and shows real-time control of non-Hermitian dynamics in open quantum systems.

Findings

Observation of two types of Liouvillian exceptional points

Real-time tuning of non-Hermitian dynamics

Chiral state transfer induced by non-Hermiticity

Abstract

Open quantum systems interacting with an environment exhibit dynamics described by the combination of dissipation and coherent Hamiltonian evolution. Taken together, these effects are captured by a Liouvillian superoperator. The degeneracies of the (generically non-Hermitian) Liouvillian are exceptional points, which are associated with critical dynamics as the system approaches steady state. We use a superconducting transmon circuit coupled to an engineered environment to observe two different types of Liouvillian exceptional points that arise either from the interplay of energy loss and decoherence or purely due to decoherence. By dynamically tuning the Liouvillian superoperators in real time we observe a non-Hermiticity-induced chiral state transfer. Our study motivates a new look at open quantum system dynamics from the vantage of Liouvillian exceptional points, enabling applications of non-Hermitian dynamics in the understanding and control of open quantum systems.