Controllable Single Cooper Pair Splitting in Hybrid Quantum Dot Systems

TL;DR

This paper demonstrates a method to controllably split and detect single Cooper pairs in a hybrid quantum dot system, overcoming limitations of previous voltage-biased setups and enabling better entanglement studies.

Contribution

It introduces a novel multi-quantum-dot device that isolates Cooper pairs from reservoirs and employs dispersive gate sensing and parity detection for controlled splitting and measurement.

Findings

Successful identification of a coherent Cooper pair splitting transition

Implementation of a double quantum dot as an electron parity sensor

Ability to control and detect single Cooper pairs in an isolated system

Abstract

Cooper pair splitters hold utility as a platform for investigating the entanglement of electrons in Cooper pairs, but probing splitters with voltage-biased Ohmic contacts prevents the retention of electrons from split pairs since they can escape to the drain reservoirs. We report the ability to controllably split and retain single Cooper pairs in a multi-quantum-dot device isolated from lead reservoirs, and separately demonstrate a technique for detecting the electrons emerging from a split pair. First, we identify a coherent Cooper pair splitting charge transition using dispersive gate sensing at GHz frequencies. Second, we utilize a double quantum dot as an electron parity sensor to detect parity changes resulting from electrons emerging from a superconducting island.