Bell inequality of frequency-bin entangled photon pairs with time-resolved detection

TL;DR

This paper demonstrates the generation of frequency-bin entangled narrowband biphotons and tests the CHSH Bell inequality using time-resolved detection, showing a violation that confirms quantum nonlocality.

Contribution

It is the first to test Bell inequality with frequency-bin entangled photons using time-resolved detection, revealing nonlocal temporal correlations.

Findings

Maximum |S| value of 2.52+/-0.48 violating Bell inequality

Generation of narrowband frequency-bin entangled biphotons

Application potential in quantum information processing

Abstract

Entanglement, describing the inseparability of a quantum multiparty system, is one of the most intriguing features of quantum mechanics. Violation of Bell inequality, for ruling out the possibility of local hidden variable theories, is commonly used as a strong witness for quantum entanglement. In previous Bell test experiments with photonic entanglement based on two-photon coincidence measurement, the photon temporal wave packets are absorbed completely by the detectors. That is, the photon coherence time is much shorter than the detection time window. Here we demonstrate generation of frequency-bin entangled narrowband biphotons, and for the first time, test the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality |S|<= 2 for their nonlocal temporal correlations with time-resolved detection. We obtain a maximum |S| value of 2.52+/-0.48 that violates the CHSH inequality. Our result will have applications in quantum information processing involving time-frequency entanglement.