Integrated quantum optical phase sensor in thin film lithium niobate

TLDR

Quantum noise from the random arrival of photons limits optical phase sensors, but engineered squeezed states can suppress this noise and enable sensitivity beyond the quantum noise limit. The study aims to develop deployable quantum sensors that harness quantum light. A photonic integrated circuit on thin‑film lithium niobate uses its second‑order nonlinearity to generate a squeezed state at the pump frequency and implements electro‑optic control for circuit operation and sensing. Using 26.2 mW of optical power, the device achieved 2.7 ± 0.2 % squeezing, which improved the signal‑to‑noise ratio of phase measurements, and the authors anticipate that such low‑power, fully integrated systems will broaden quantum optical sensing applications.

Abstract

Abstract The quantum noise of light, attributed to the random arrival time of photons from a coherent light source, fundamentally limits optical phase sensors. An engineered source of squeezed states suppresses this noise and allows phase detection sensitivity beyond the quantum noise limit (QNL). We need ways to use quantum light within deployable quantum sensors. Here we present a photonic integrated circuit in thin-film lithium niobate that meets these requirements. We use the second-order nonlinearity to produce a squeezed state at the same frequency as the pump light and realize circuit control and sensing with electro-optics. Using 26.2 milliwatts of optical power, we measure (2.7 ± 0.2)% squeezing and apply it to increase the signal-to-noise ratio of phase measurement. We anticipate that photonic systems like this, which operate with low power and integrate all of the needed functionality on a single die, will open new opportunities for quantum optical sensing.