Real-time observation of Cooper pair splitting showing strong non-local correlations

The splitting of Cooper pairs in superconductors has been challenging to detect experimentally. Here, the authors observe the real-time splitting of individual Cooper pairs in a superconducting device. Controlled generation and detection of quantum entanglement between spatially separated particles constitute an essential prerequisite both for testing the foundations of quantum mechanics and for realizing future quantum technologies. Splitting of Cooper pairs from a superconductor provides entangled electrons at separate locations. However, experimentally accessing the individual split Cooper pairs constitutes a major unresolved issue as they mix together with electrons from competing processes. Here, we overcome this challenge with the first real-time observation of the splitting of individual Cooper pairs, enabling direct access to the time-resolved statistics of Cooper pair splitting. We determine the correlation statistics arising from two-electron processes and find a pronounced peak that is two orders of magnitude larger than the background. Our experiment thereby allows to unambiguously pinpoint and select split Cooper pairs with 99% fidelity. These results open up an avenue for performing experiments that tap into the spin-entanglement of split Cooper pairs.

Automated summary

Detecting the splitting of Cooper pairs in superconductors has been a challenge, but in this study, the authors successfully observed the real-time splitting of individual Cooper pairs in a superconducting device. By overcoming the challenge of accessing split Cooper pairs, the researchers were able to statistically analyze the correlation arising from two-electron processes with significant results. This breakthrough offers new possibilities for experiments involving the spin-entanglement of split Cooper pairs.