Flux-pump induced degradation of $T_1$ for dissipative cat qubits

TL;DR

This paper investigates how flux-pump induced effects can degrade the relaxation time ($T_1$) of dissipative cat qubits in superconducting circuits, providing insights for improving qubit stability.

Contribution

It derives an effective master equation for an asymmetrically threaded SQUID circuit and analyzes relaxation processes under drives using advanced perturbation and Floquet theories.

Findings

Spurious single-photon decay rates increase under parametric pumping.

Analysis informs mitigation strategies for flux-pump induced degradation.

Methods can be extended to other circuit implementations.

Abstract

Dissipative stabilization of cat qubits autonomously corrects for bit flip errors by ensuring that reservoir-engineered two-photon losses dominate over other mechanisms inducing phase flip errors. To describe the latter, we derive an effective master equation for an asymmetrically threaded SQUID based superconducting circuit used to stabilize a dissipative cat qubit. We analyze the dressing of relaxation processes under drives in time-dependent Schrieffer-Wolff perturbation theory for weakly anharmonic bosonic degrees of freedom, and in numerically exact Floquet theory. We find that spurious single-photon decay rates can increase under the action of the parametric pump that generates the required interactions for cat-qubit stabilization. Our analysis feeds into mitigation strategies that can inform current experiments, and the methods presented here can be extended to other circuit implementations.