Two-mode squeezed vacuum and squeezed light in correlated interferometry

TL;DR

This paper explores how injecting quantum light, specifically two-mode squeezed vacuum, into correlated interferometers can surpass shot-noise limits, improving detection of faint correlated signals like holographic noise.

Contribution

It demonstrates the potential of using two-mode squeezed vacuum to enhance phase-correlation measurements in interferometry beyond classical limits.

Findings

Quantum light reduces photon noise below shot-noise levels.

Two-mode squeezed vacuum enhances phase-correlation detection.

Entanglement offers surprising uncertainty reduction in correlated interferometry.

Abstract

We study in detail a system of two interferometers aimed to the detection of extremely faint phase-fluctuations. This system can represent a breakthrough for detecting a faint correlated signal that would remain otherwise undetectable even using the most sensitive individual interferometric devices, that are limited by the shot noise. If the two interferometers experience identical phase-fluctuations, like the ones introduced by the so called "holographic noise", this signal should emerge if their output signals are correlated, while the fluctuations due to shot noise and other independent contributions will vanish. We show how the injecting quantum light in the free ports of the interferometers can reduce the photon noise of the system beyond the shot-noise, enhancing the resolution in the phase-correlation estimation. We analyze both the use of two-mode squeezed vacuum or twin-beam state (TWB) and of two independent squeezing states. Our results basically confirms the benefit of using squeezed beams together with strong coherent beams in interferometry, even in this correlated case. However, mainly we concentrate on the possible use of TWB, discovering interesting and probably unexplored areas of application of bipartite entanglement and in particular the possibility of reaching in principle surprising uncertainty reduction.