Spectral densities of superconducting qubits with environmental resonances

TL;DR

This paper derives the environmental spectral density for various superconducting qubits coupled to resonant environments, revealing how these interactions influence relaxation times and identifying conditions for enhanced qubit lifetimes.

Contribution

It provides a detailed derivation of spectral densities for flux, phase, and charge qubits with environmental resonances, and analyzes their impact on relaxation times.

Findings

Spectral densities are derived for different qubit types with environmental resonances.

Relaxation times $T_1$ are calculated from spectral densities.

Enhanced $T_1$ occurs beyond the environmental resonance frequency.

Abstract

In this paper we derive the environmental spectral density for flux, phase and charge qubits when each of them is coupled to an environment with a resonance. From the spectral density we obtain the characteristic spontaneous emission (relaxation) lifetimes $T_1$ for each of these qubits, and show that there is a substantial enhancement of $T_1$ beyond the resonant frequency of the environment.