Integrated time-bin entangled quantum light source on a 4H-SiC microring chip

TL;DR

This paper reports an optimized integrated silicon carbide microring resonator that generates high-rate, broadband time-bin entangled photon pairs with high fidelity, advancing scalable quantum communication technologies.

Contribution

It introduces a novel design that balances cavity quality factor and bandwidth, enabling efficient, broadband, high-rate entangled photon-pair generation on a 4H-SiC platform.

Findings

Achieved a photon-pair generation rate of 1.35×10^7 s^-1 mW^-2.

Measured a raw visibility of 95.55%, violating Bell's inequality significantly.

Obtained a quantum state fidelity of 94.37%.

Abstract

Integrated time-bin-entangled photon-pair source with cavity-enhanced nonlinear optical processes is essential for quantum information technologies. However, microcavities with a high quality factor inherently introduce a trade-off between generation efficiency and photon bandwidth, which hinders the development of high-speed quantum networks with an integrated source. Here, we address this challenge by optimizing the nonlinearity property of the material and the geometry of the integrated microring resonator with a 4H-silicon carbide platform. Operating at a loaded quality factor of 1.9 $\times$ 10^5 - spectral bandwidth of 1.0 GHz and pumped with 300-ps double pulses separated by 1.25 ns at a repetition rate of 160 MHz, the device achieves a time-bin-entangled photon-pair generation rate of 1.35 $\times$ 10^7 s^-1 mW^-2. A raw visibility of 95.55 $\pm$ 0.18% is measured, showing a violation of Bell's inequality by more than 138 standard deviations, and a fidelity of 94.37 $\pm$ 0.22% is obtained by quantum state tomography. These results provide a scalable pathway to an efficient and broadband time-bin entangled quantum light source, overcoming intrinsic limitations of cavity-based designs and advancing integrated platforms for future quantum communication networks.