Entangled photon triplets using lithium niobate nanophotonics

TL;DR

This paper demonstrates a highly efficient method for generating entangled photon triplets using integrated lithium niobate nanophotonics, significantly surpassing previous efficiencies and paving the way for practical quantum communication and computation.

Contribution

The authors integrated two cascaded down-converters on a lithium niobate waveguide, achieving a record efficiency of 237 kHz/mW for triplet photon generation, which is an order of magnitude higher than prior methods.

Findings

Achieved a triplet generation rate of 237 kHz/mW.

Demonstrated a second down-converter probability of 4.4 x 10^-5.

Path towards MHz triplet rates for quantum applications.

Abstract

Multiphoton states are needed for quantum communication and computation. Multiphoton states are significantly more difficult to generate than one- and two-photon states because two individual down-conversion processes must be cascaded. Only efficiencies of $<100$ Hz/mW have been reported to date. We integrate two down-converters on the same thin-film lithium niobate waveguide, significantly enhancing the cascaded process efficiency to $237 \pm 36$ kHz/mW. The measured $4.4 \times 10^{-5}$ probability of the second down-converter, which sets the limit on detectable triplet rates, exceeds those of previous triplet sources by an order of magnitude and demonstrates a path towards MHz rates of triplets for quantum applications.