Improving the phase super-sensitivity of squeezing-assisted interferometers by squeeze factor unbalancing

TL;DR

This paper investigates how unbalancing the gain in squeezing-assisted interferometers enhances phase super-sensitivity, allowing sensitivities to surpass the shot-noise limit across broader phase ranges.

Contribution

It introduces the concept that gain unbalancing in SU(1,1) and related interferometers improves phase super-sensitivity and broadens the operational phase range.

Findings

Gain unbalancing enhances super-sensitivity.

Broader phase range for surpassing shot-noise limit.

Improved overall sensitivity with gain unbalancing.

Abstract

The sensitivity properties of an SU(1,1) interferometer made of two cascaded parametric amplifiers, as well as of an ordinary SU(2) interferometer preceded by a squeezer and followed by an anti-squeezer, are theoretically investigated. Several possible experimental configurations are considered, such as the absence or presence of a seed beam, direct or homodyne detection scheme. In all cases we formulate the optimal conditions to achieve phase super-sensitivity, meaning a sensitivity overcoming the shot-noise limit. We show that for a given gain of the first parametric amplifier, unbalancing the interferometer by increasing the gain of the second amplifier improves the interferometer properties. In particular, a broader super-sensitivity phase range and a better overall sensitivity can be achieved by gain unbalancing.