Probing Cooper Pairs with Franson Interferometry

TL;DR

This paper proposes a Franson interferometry-based setup to analyze the coherence properties of Cooper pairs emitted from a superconductor, enabling measurement of their internal coherence and center-of-mass de Broglie wavelength through current correlations.

Contribution

It introduces a novel interferometric method to probe Cooper pair coherence and motion, linking measurable current correlations to fundamental superconducting properties.

Findings

Cooper pair internal coherence length can be measured.

Center-of-mass de Broglie wavelength of pairs can be determined.

The setup enables direct probing of superconducting coherence properties.

Abstract

A setup based on the Franson optical interferometer is analyzed, which allows us to detect the coherence properties of Cooper pairs emerging via tunneling from a superconductor in contact with two one-dimensional channels. By tuning the system parameters we show that both the internal coherence of the emitted Cooper pairs, which is proportional to Pippard's length, and the de Broglie wavelength of their center-of-mass motion can be measured via current-current correlation measurements.