Lifting the Bandwidth Limit of Optical Homodyne Measurement

TL;DR

This paper introduces a broadband optical homodyne measurement technique that overcomes traditional bandwidth limitations, enabling simultaneous quadrature measurements across 55 THz and enhancing quantum information processing capabilities.

Contribution

The authors develop a fully parallel optical homodyne measurement method using optical parametric amplification, lifting the bandwidth restriction of standard homodyne detection.

Findings

Measured two-mode quadrature squeezing of 1.7dB below vacuum level

Achieved broadband measurement across 55 THz

Demonstrated robustness to detection inefficiency with >50% loss

Abstract

Homodyne measurement is a corner-stone of quantum optics. It measures the fundamental variables of quantum electrodynamics - the quadratures of light, which represent the cosine-wave and sine-wave components of an optical field and constitute the quantum optical analog of position and momentum. Yet, standard homodyne, which is used to measure the quadrature information, suffers from a severe bandwidth limitation: While the bandwidth of optical states can easily span many THz, standard homodyne detection is inherently limited to the electrically accessible, MHz to GHz range, leaving a dramatic gap between the relevant optical phenomena and the measurement capability. We demonstrate a fully parallel optical homodyne measurement across an arbitrary optical bandwidth, effectively lifting this bandwidth limitation completely. Using optical parametric amplification, which amplifies one quadrature while attenuating the other, we measure two-mode quadrature squeezing of 1.7dB below the vacuum level simultaneously across a bandwidth of 55THz, using just one local-oscillator - the pump. As opposed to standard homodyne, our measurement is highly robust to detection inefficiency, and was obtained with $>50\%$ loss in the detection channel. This broadband parametric homodyne measurement opens a wide window for parallel processing of quantum information.