Intrinsic mechanisms for drive-dependent Purcell decay in superconducting quantum circuits

TL;DR

This paper introduces an analytic approach to understanding how the photonic population in a cavity affects the intrinsic Purcell decay rate of superconducting qubits, revealing new phenomena and physical insights.

Contribution

It provides a new analytic method combining Keldysh and Lindblad theories to predict drive-dependent Purcell decay in superconducting qubits, with good agreement to numerical simulations.

Findings

Cavity-qubit detuning controls Purcell decay dependence on photon number.

The method predicts new phenomena related to drive-dependent decay.

Analytic expressions match full master equation results.

Abstract

We develop a new approach to understanding intrinsic mechanisms that cause the $T_1$-decay rate of a multi-level superconducting qubit to depend on the photonic population of a coupled, detuned cavity. Our method yields simple analytic expressions for both the coherently driven or thermally excited cases which are in good agreement with full master equation numerics, and also facilitates direct physical intuition. It also predicts several new phenomena. In particular, we find that in a wide range of settings, the cavity-qubit detuning controls whether a non-zero photonic population increases or decreases qubit Purcell decay. Our method combines insights from a Keldysh treatment of the system, and Lindblad perturbation theory.