# Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

## TL;DR

This paper demonstrates broadband quadrature squeezing and nonclassical photon correlations generated in a silicon nitride nanophotonic device, advancing integrated quantum optics with high-quality squeezing and photon number correlations.

## Contribution

It reports the first integrated nanophotonic device producing broadband quadrature and photon number difference squeezing with high efficiency and multi-photon detection capabilities.

## Key findings

- 1.0 dB broadband quadrature squeezing achieved
- 1.5 dB photon number difference squeezing observed
- Multi-photon events over 10 photons detected at record rates

## Abstract

We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition edge sensors. We measure $1.0(1)$~dB of broadband quadrature squeezing (${\sim}4$~dB inferred on-chip) and $1.5(3)$~dB of photon number difference squeezing (${\sim}7$~dB inferred on-chip). Nearly-single temporal mode operation is achieved, with measured raw unheralded second-order correlations $g^{(2)}$ as high as $1.95(1)$. Multi-photon events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology.