Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

TL;DR

This paper proposes a method to transfer the spin entanglement of split Cooper pairs onto optical photons, enabling Bell inequality violation tests to confirm nonlocal electron entanglement.

Contribution

It introduces a scheme to convert Cooper pair spin states into optical photon polarization states for entanglement verification.

Findings

Photon pairs violate Bell inequality, confirming entanglement.

Method enables optical detection of electron entanglement.

Proposes a practical test for nonlocal Cooper pair entanglement.

Abstract

Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.