Single Cooper-pair pumping in the adiabatic limit and beyond

TL;DR

This paper demonstrates precise control of single Cooper-pair transfer using an rf-driven sluice, explores the limits of adiabaticity, and models the effects of decoherence and Landau-Zener transitions in the system.

Contribution

It introduces a method for controlled single Cooper-pair pumping and analyzes the breakdown of adiabatic dynamics with a quantitative model including decoherence.

Findings

Successful single Cooper-pair pumping per cycle.

Observation of crossover between pure and mixed Cooper-pair-quasiparticle transport.

Quantitative modeling of Landau-Zener transitions with decoherence effects.

Abstract

We demonstrate controlled pumping of Cooper pairs down to the level of a single pair per cycle, using an rf-driven Cooper-pair sluice. We also investigate the breakdown of the adiabatic dynamics in two different ways. By transferring many Cooper pairs at a time, we observe a crossover between pure Cooper-pair and mixed Cooper-pair-quasiparticle transport. By tuning the Josephson coupling that governs Cooper-pair tunneling, we characterize Landau-Zener transitions in our device. Our data are quantitatively accounted for by a simple model including decoherence effects.