Highly efficient entanglement swapping and teleportation at telecom wavelength

TL;DR

This paper demonstrates a significant improvement in entanglement swapping and teleportation efficiency at telecom wavelengths using ultra-bright photon sources and high-efficiency detectors, enabling practical quantum communication applications.

Contribution

The authors achieved a four-fold increase in coincidence count rate at telecom wavelengths, surpassing previous experiments and paving the way for practical quantum networks.

Findings

Achieved a coincidence count rate of 10^8 counts/sec

Obtained a Hong-Ou-Mandel interference visibility of 73.3% raw, 85.1% net

Fidelity of 76.3% in entanglement swapping

Abstract

Entanglement swapping at telecom wavelengths is at the heart of quantum networking in optical fiber infrastructures. Although entanglement swapping has been demonstrated experimentally so far using various types of entangled photon sources both in near-infrared and telecom wavelength regions, the rate of swapping operation has been too low to be applied to practical quantum protocols, due to limited efficiency of entangled photon sources and photon detectors. Here we demonstrate drastic improvement of the efficiency at telecom wavelength by using two ultra-bright entangled photon sources and four highly efficient superconducting nanowire single photon detectors.We have attained a four-fold coincidence count rate of 108 counts per second, which is three orders higher than the previous experiments at telecom wavelengths. A raw (net) visibility in a Hong-Ou-Mandel interference between the two independent entangled sources was 73.3 $\pm$ 1.0% (85.1 $\pm$ 0.8%). We performed the teleportation and entanglement swapping, and obtained a fidelity of 76.3% in the swapping test.Our results on the coincidence count rates are comparable with the ones ever recorded in teleportation/swaping and multi-photon entanglement generation experiments at around 800\,nm wavelengths. Our setup opens the way to practical implementation of device-independent quantum key distribution and its distance extension by the entanglement swapping as well as multi-photon entangled state generation in telecom band infrastructures with both space and fiber links.