Strong nanophotonic quantum squeezing exceeding 3.5 dB in a foundry-compatible Kerr microresonator

TL;DR

This paper demonstrates a foundry-compatible silicon nitride microresonator that achieves over 3.5 dB of quantum squeezing, advancing on-chip quantum light sources for quantum information and metrology.

Contribution

It reports the first robust, on-chip quantum squeezing exceeding 3.5 dB in a CMOS-compatible silicon nitride microresonator platform.

Findings

Achieved 3.7 ± 0.2 dB of directly detected squeezing.

Inferred on-chip squeezing level of 10.7 dB.

Squeezing is stable across devices and pump conditions.

Abstract

Squeezed light, with its quantum noise reduction capabilities, has emerged as a powerful resource in quantum information processing and precision metrology. To reach noise reduction levels such that a quantum advantage is achieved, off-chip squeezers are typically used. The development of on-chip squeezed light sources, particularly in nanophotonic platforms, has been challenging. We report 3.7 $\pm$ 0.2 dB of directly detected nanophotonic quantum squeezing using foundry-fabricated silicon nitride (Si$_3$N$_4$) microrings with an inferred squeezing level of 10.7 dB on-chip. The squeezing level is robust across multiple devices and pump detunings, and is consistent with the overcoupling degree without noticeable degradation from excess classical noise. We also offer insights to mitigate thermally-induced excess noise, that typically degrades squeezing, by using small-radius rings with a larger free spectral range (450 GHz) and consequently lower parametric oscillation thresholds. Our results demonstrate that Si$_3$N$_4$ is a viable platform for strong quantum noise reduction in a CMOS-compatible, scalable architecture.