Massive-mode polarization entangled biphoton frequency comb

TL;DR

This paper reports the generation of a polarization-entangled biphoton frequency comb with over 1400 modes, significantly surpassing previous capabilities, which could enhance high-capacity quantum communication systems.

Contribution

The authors demonstrate a massively multimode polarization-entangled biphoton frequency comb using a novel resonator setup, greatly expanding the number of entangled frequency modes.

Findings

Over 1400 frequency modes in the entangled biphoton frequency comb.

Fidelity of over 0.7 in quantum state tomography for selected modes.

Potential to increase quantum communication capacity.

Abstract

A frequency-multiplexed entangled photon pair and a high-dimensional hyperentangled photon pair are useful to realize a high-capacity quantum communication. A biphoton frequency comb (BFC) with entanglement can be used to prepare both states. We demonstrate polarization entangled BFCs with over 1400 frequency modes, which is approximately two orders of magnitude larger than those of earlier entangled BFCs, by placing a singly resonant periodically poled LiNbO3 waveguide resonator within a Sagnac loop. The BFCs are demonstrated by measuring the joint spectral intensity, cross-correlation, and autocorrelation. Moreover, the polarization entanglement at representative groups of frequency modes is verified by quantum state tomography, where each fidelity is over 0.7. The efficient generation of a massive-mode entangled BFC is expected to accelerate the increase of capacity in quantum communication.