Chip-integrated visible–telecom entangled photon pair source for quantum communication

Abstract

Photon pair sources are fundamental building blocks for quantum entanglement and quantum communication. Recent studies in silicon photonics have documented promising characteristics for photon pair sources within the telecommunications band, including sub-milliwatt optical pump power, high spectral brightness, and high photon purity. However, most quantum systems suitable for local operations, such as storage and computation, support optical transitions in the visible or short near-infrared bands. In comparison to telecommunications wavelengths, the significantly higher optical attenuation in silica at such wavelengths limits the length scale over which optical-fiber-based quantum communication between such local nodes can take place. One approach to connect such systems over fiber is through a photon pair source that can bridge the visible and telecom bands, but an appropriate source, which should produce narrow-band photon pairs with a high signal-to-noise ratio, has not yet been developed. Here, we demonstrate an on-chip visible-telecom photon pair source for the first time, using high quality factor silicon nitride microresonators to generate bright photon pairs with an unprecedented coincidence-to-accidental ratio (CAR) up to (3.8 ± 0.2) × 103. We further demonstrate dispersion engineering of the microresonators to enable the connection of different species of trapped atoms/ions, defect centers, and quantum dots to the telecommunications bands for future quantum communication systems.

Building Blocks for Quantum Network Based on Group‐IV Split‐Vacancy Centers in Diamond

“…For inter‐metropolitan fiber‐based quantum networks, telecom or near‐telecom wavelength emission is needed so as to take advantage of low‐loss transmission window granted by the silica optical fiber, which is probably the only financially affordable option for large‐scale deployment of long‐distance communication. The wavelength compatibility has been realized on multiple systems including emergent emitters in GaN, defects in SiC, doping of carbon nanotubes, and rare‐earth Er 3+ ions in solids, but not yet on split‐vacancy color centers, which require different techniques of frequency downconversion similar to those applied to semiconductor quantum dots . Secondly, mK cryogenic temperature operation on SiV − center is too costly and cumbersome for any practical usage of the long memory lifetime.…”

Integrated photonic quantum technologies

“…A range of optical waveguide systems have been developed for IQP, including laser-writing silica [19][20][21][22], silica-on-insulator (SiO 2 ) [14,[16][17][18], silicon-on-insulator (Si) [23][24][25][26], silicon nitride (Si 3 N 4 ) [27][28][29][30], lithium niobate (LN) [31][32][33], gallium arsenide (GaAs) [34][35][36], indium phosphide (InP) [37,38], and others. We refer detailed discussions on the IQP platforms in other reviews, while here highlight a few of them.…”

Milliwatt-threshold visible–telecom optical parametric oscillation using silicon nanophotonics

“…For example, recent work reporting telecom-to-visible spectral translation via stimulated dFWM did not exhibit widely-separated OPO, because without the seed telecom light, close-to-pump OPO processes dominate 28 . Thus, unlike previous work in wide-band silicon nonlinear nanophotonics [23][24][25][26]28,29 , visible-telecom OPO faces a more stringent requirement not only on enhancing the process of interest, but also on suppressing all competing processes at the same time.…”