Adiabatic Cooper pair splitter

TL;DR

This paper proposes an adiabatic Cooper pair splitter that generates spin-entangled electrons with quantized current and robustness against imperfections, operable at gigahertz frequencies, advancing quantum information processing.

Contribution

It introduces a novel adiabatic scheme for Cooper pair splitting that does not require fine-tuning and achieves quantized, high-frequency operation.

Findings

The splitter produces quantized currents proportional to the drive frequency.

The scheme is robust against experimental imperfections.

Operation in the gigahertz regime is feasible.

Abstract

Recent experiments have observed Cooper pair splitting in quantum dots coupled to superconductors, and efficient schemes for controlling and timing the splitting process are now called for. Here, we propose and analyze an adiabatic Cooper pair splitter that can produce a regular flow of spin-entangled electrons in response to a time-dependent and periodic gate voltage. The splitting process is controlled by moving adiabatically back and forth along an avoided crossing between the empty state and the singlet state of two quantum dots that are coupled to a superconductor, followed by the emission of the split Cooper pairs into two normal-state drains. The scheme does not rely on fine-tuned resonance conditions and is therefore robust against experimental imperfections in the driving signal. We identify a range of driving frequencies, where the output currents are quantized and proportional to the driving frequency combined with suppressed low-frequency noise. We also discuss the main sources of cycle-missing events and evaluate the statistics of electrons emitted within a period of the drive as well as the distribution of waiting times between them. Realistic parameter estimates indicate that the Cooper pair splitter can be operated in the gigahertz regime.