Quantum State Tomography in a Third-Order Integrated Optical Parametric Oscillator

TL;DR

This paper reports on the measurement of quantum states in a third-order integrated optical parametric oscillator, highlighting the generation of squeezing and the challenges in achieving entanglement due to phase noise.

Contribution

It provides the first detailed covariance matrix measurement of an integrated third-order optical parametric oscillator operating above threshold, revealing the effects of phase noise on quantum correlations.

Findings

Observed up to 2.3 dB of amplitude difference squeezing

Inferred 4.9 dB of on-chip squeezing

Identified phase noise as a barrier to entanglement

Abstract

We measured the covariance matrix of the fields generated in an integrated third-order optical parametric oscillator operating above threshold. We observed up to $(2.3 \pm 0.3)$ dB of squeezing in amplitude difference, inferred $(4.9 \pm 0.7)$ dB of on-chip squeezing, while an excess of noise for the sum of conjugated quadratures hinders the entanglement. The degradation of amplitude correlations and state purity for the increasing of the pump power is consistent with the observed growth of the phase noise of the fields, showing the necessity of strategies for phase noise control aiming at entanglement generation in these systems.