Cooper pair current in the presence of flux noise

TL;DR

This paper investigates how flux noise affects Cooper pair current and pumping, introducing a generalized current definition that includes environmental contributions, and demonstrates how to engineer flux noise effects via external circuits.

Contribution

It generalizes the current definition to include environment-induced effects and provides a numerical framework to analyze flux noise impact on Cooper pair transport.

Findings

Dissipative current vanishes for charge noise but persists for flux noise.

The pumped charge depends on the coupling to the external environment.

A method to engineer flux noise effects using an external circuit is proposed.

Abstract

We study the effect of the flux noise on the Cooper pair current and pumping. We generalize the definition of the current in order to take into account the contribution induced by the environment. It turns out that this dissipative current vanishes for charge noise but it is finite in general for noise operators that do not commute with the charge operator. We discuss in a generic framework the effect of flux noise and present a way to engineer it by coupling the system to an additional external circuit. We calculate numerically the pumped charge through the device by solving the master equation for the reduced density matrix of the system and show how it depends on the coupling to the artificial environment.