Cross time-bin photonic entanglement for quantum key distribution

TL;DR

This paper presents a fibered source of cross time-bin entangled photons at 1540 nm, simplifying quantum key distribution setups and demonstrating high-visibility interference tests confirming non-classical correlations.

Contribution

The work introduces a phase-stabilization-free, fully fibered source of cross time-bin entangled photons suitable for quantum key distribution.

Findings

Two-photon interference visibility >95%

Non-classical correlations confirmed without active stabilization

Source is suitable for time-bin quantum key distribution

Abstract

We report a fully fibered source emitting cross time-bin entangled photons at 1540 nm from type-II spontaneous parametric down conversion. Compared to standard time-bin entanglement realizations, the preparation interferometer requires no phase stabilization, simplifying its implementation in quantum key distribution experiments. Franson/Bell-type tests of such a cross time-bin state are performed and lead to two-photon interference raw visibilities greater than 95%, which are only limited by the dark-counts in the detectors and imperfections in the analysis system. Just by trusting the randomness of the beam-splitters, the correlations generated by the source can be proved of non-classical origin even in a passive implementation. The obtained results confirm the suitability of this source for time-bin based quantum key distribution.