Dynamical Coulomb blockade and spin-entangled electrons

TL;DR

This paper explores how dynamical Coulomb blockade effects can be used to generate and control spin-entangled electron pairs from a superconductor, with implications for quantum information processing.

Contribution

It introduces a phenomenological model showing how electromagnetic environment coupling enhances entangled pair production and analyzes spatial correlations affecting tunneling processes.

Findings

Enhanced entangled pair tunneling into the same lead due to Coulomb blockade.

Weaker spatial correlation effects in lower-dimensional superconductors.

Current suppression depends on the distance between tunnel junctions.

Abstract

We consider the production of mobile and nonlocal pairwise spin-entangled electrons from tunneling of a BCS-superconductor (SC) to two normal Fermi liquid leads. The necessary mechanism to separate the two electrons coming from the same Cooper pair (spin-singlet) is achieved by coupling the SC to leads with a finite resistance. The resulting dynamical Coulomb blockade effect, which we describe phenomenologically in terms of an electromagnetic environment, is shown to be enhanced for tunneling of two spin-entangled electrons into the same lead compared to the process where the pair splits and each electron tunnels into a different lead. On the other hand in the pair-split process, the spatial correlation of a Cooper pair leads to a current suppression as a function of distance between the two tunnel junctions which is weaker for effectively lower dimensional SCs.