The effect of environmental coupling on tunneling of quasiparticles in Josephson junctions

TL;DR

This paper investigates how the electromagnetic environment influences quasiparticle tunneling in Josephson junctions, revealing mechanisms that affect qubit coherence and identifying conditions that suppress environmental coupling for improved superconducting qubits.

Contribution

It presents a nonperturbative analysis of environmental effects on quasiparticle tunneling, highlighting processes that impact charge transfer and phase coherence in Josephson junctions.

Findings

Environmental coupling can be suppressed in many setups, reducing quasiparticle decay.

Charge superpositions are sensitive to phase diffusion, even at zero temperature.

Better qubit coherence is achievable due to reduced environmental effects.

Abstract

We study quasiparticle tunneling in Josephson tunnel junctions embedded in an electromagnetic environment. We identify tunneling processes that transfer electrical charge and couple to the environment in a way similar to that of normal electrons, and processes that mix electrons and holes and are thus creating charge superpositions. The latter are sensitive to the phase difference between the superconductor and are thus limited by phase diffusion even at zero temperature. We show that the environmental coupling is suppressed in many environments, thus leading to lower quasiparticle decay rates and thus better superconductor qubit coherence than previously expected. Our approach is nonperturbative in the environmental coupling strength.