Nanophotonic source of broadband quadrature squeezing

TL;DR

This paper demonstrates GHz-broad quadrature squeezing on a CMOS-compatible silicon nitride chip, marking progress in integrated quantum photonics for scalable quantum technologies.

Contribution

It reports the first measurement of broadband quadrature squeezing on an integrated silicon nitride photonic chip using CMOS-compatible fabrication.

Findings

Achieved 0.45 dB of on-chip quadrature squeezing.

Corrected squeezing level of 1 dB below Shot Noise after losses.

Identified excess noise as a current limitation and proposed mitigation strategies.

Abstract

Squeezed light are optical beams with variance below the Shot Noise Level. They are a key resource for quantum technologies based on photons, they can be used to achieve better precision measurements, improve security in quantum key distribution channels and as a fundamental resource for quantum computation. To date, the majority of experiments based on squeezed light have been based on non-linear crystals and discrete optical components, as the integration of quadrature squeezed states of light in a nanofabrication-friendly material is a challenging technological task. Here we measure 0.45 dB of GHz-broad quadrature squeezing produced by a ring resonator integrated on a Silicon Nitride photonic chip that we fabricated with CMOS compatible steps. The result corrected for the off-chip losses is estimated to be 1 dB below the Shot Noise Level. We identify and verify that the current results are limited by excess noise produced in the chip, and propose ways to reduce it. Calculations suggest that an improvement in the optical properties of the chip achievable with existing technology can develop scalable quantum technologies based on light.