Is relaxation correlated in superconducting qubits?

TL;DR

This paper investigates how coupled superconducting qubits exhibit collective relaxation phenomena, revealing stable entangled states and superradiant effects due to global environmental coupling, with potential experimental applications.

Contribution

It demonstrates that collective relaxation preserves Dicke states in superconducting qubits and proposes experimental methods to observe and utilize these effects.

Findings

Existence of stable entangled states under collective relaxation

Presence of superradiant and subradiant states in coupled qubits

Potential for creating long-lived entangled states experimentally

Abstract

We consider coupled quantum two-state systems (qubits) exposed to a global relaxation process. The global relaxation refers to the assumption that qubits are coupled to the same quantum bath with approximately equal strengths, appropriate for long-wavelength environmental fluctuations. We show that interactions do not spoil the picture of Dicke's subradiant and superradiant states where quantum interference effects lead to striking deviations from the independent relaxation picture. Remarkably, the system possess a stable entangled state and a state decaying faster than single qubit excitations. We propose a scheme how these effects can be experimentally accessed in superconducting flux qubits and, possibly, used in constructing long-lived entangled states.