# High-Rate Photon Pairs and Sequential Time-Bin Entanglement with Si$_3$N$_4$ Ring Microresonators

## TL;DR

This paper demonstrates high-rate photon pair generation and sequential time-bin entanglement using silicon nitride ring microresonators on photonic chips, advancing quantum communication technology.

## Contribution

It introduces a novel integrated silicon nitride microresonator platform for efficient photon pair production and a simple noise characterization technique for system optimization.

## Key findings

- Photon pairs generated at 80,000 per second.
- Sequential time-bin entanglement achieved at 750 MHz.
- Raw interference visibility exceeds 98%.

## Abstract

Integrated photonics is increasing in importance for compact, robust, and scalable enabling quantum technologies. This is particularly interesting for developing quantum communication networks, where resources need to be deployed in the field. We exploit photonic chip-based $ \rm Si_3 N_4$ ring microresonators for the generation of photon pairs with low-loss, high-noise suppression and coincidence rates of $80\times 10^3\,$s$^{-1}$. A simple photonic noise characterisation technique is presented that distinguishes linear and nonlinear contributions that is useful for system design and optimisation. We then demonstrate an all-fibre $750\,$MHz clock-rate sequential Time-Bin entanglement scheme with raw interference visibilities $>\,98\,\%$.