Long-range Cooper pair splitter with high entanglement production rate

TL;DR

This paper proposes a long-range Cooper pair splitter in an NSN junction driven by supercurrent, significantly increasing entanglement production efficiency and enabling novel entangled states with equal energy.

Contribution

It introduces a supercurrent-driven method to enhance crossed Andreev reflection and produce high-rate entanglement, overcoming size constraints of previous designs.

Findings

High entanglement production rate close to saturation.

Enhanced crossed Andreev reflection due to supercurrent.

Generation of novel equal-energy entangled states.

Abstract

Cooper pairs in the superconductor are a natural source of spin entanglement. The existing proposals of the Cooper pair splitter can only realize a low efficiency of entanglement production, and its size is constrained by the superconducting coherence length. Here we show that a long-range Cooper pair splitter can be implemented in a normal metal-superconductor-normal metal (NSN) junction by driving a supercurrent in the S. The supercurrent results in a band gap modification of the S, which significantly enhances the crossed Andreev reflection (CAR) of the NSN junction and simultaneously quenches its elastic cotunneling. Therefore, a high entanglement production rate close to its saturation value can be achieved by the inverse CAR. Interestingly, in addition to the conventional entangled electron states between opposite energy levels, novel entangled states with equal energy can also be induced in our proposal.