Bichromatic homodyne detection of broadband quadrature squeezing

TL;DR

This paper demonstrates a novel homodyne detection method using a two-frequency local oscillator to characterize broadband quadrature squeezing separated by over 6 GHz, enabling detailed analysis of squeezing spectra.

Contribution

It introduces a bichromatic homodyne detection technique for broadband quadrature squeezing with large frequency separation, allowing amplitude and phase characterization at low detection frequencies.

Findings

Successful detection of quadrature squeezing separated by >6 GHz

Observation of noise ellipse rotation across the squeezing spectrum

Method enables detailed spectral analysis of broadband squeezing

Abstract

We experimentally study a homodyne detection technique for the characterization of a quadrature squeezed field where the correlated bands, here created by four-wave mixing in a hot atomic vapor, are separated by a large frequency gap of more than 6 GHz. The technique uses a two-frequency local oscillator to detect the fluctuations of the correlated bands at a frequency accessible to the detection electronics. Working at low detection frequency, the method allows for the determination of both the amplitude and the phase of the squeezing spectrum. In particular, we show that the quadrature squeezing created by our four-wave mixing process displays a noise ellipse rotation of $\pi/2$ across the squeezing spectrum