Performance of hybrid entanglement photon pair source for quantum key distribution

TL;DR

This paper demonstrates a hybrid entangled photon pair source at 1550 nm and 810 nm, achieving high visibility and count rates suitable for secure quantum key distribution.

Contribution

The work introduces an experimental setup for hybrid entanglement between different degrees of freedom, with high visibilities and count rates for quantum communication.

Findings

Visibilities of 95.8% and 88% along Z-Z and X-X axes.

Coincidence count rate exceeds 800 counts per second.

Values surpass the Bell inequality violation threshold.

Abstract

We report on the experimental demonstration of a source of hybrid entanglement pairs between two different degrees of freedom, a 1550 nm time-bin qubit and an 810 nm polarization qubit. The polarization qubit at 810 nm is transformed by an asymmetric Mach-Zehnder interferometer consisted of a Glan laser prism and a polarization-maintaining fiber. We obtained visibilities of 95.8% and 88% along Z-Z and X-X axes on the Poincare sphere, respectively with a coincidence count rate of more than 800 c/s after entanglement format transformation. These values are well above the threshold of 70.7% needed to violate a Bell inequality and allow distilling a secure key in the quantum key distribution.