Coherent control of vacuum squeezing in the Gravitational-Wave Detection Band

TL;DR

This paper presents a novel coherent control scheme for stabilizing phase locking of broadband squeezed vacuum fields in the 10Hz to 10kHz range, enhancing gravitational wave detection sensitivity.

Contribution

It introduces a new control method for broadband vacuum squeezing in the gravitational wave detection band, overcoming previous limitations of conventional schemes.

Findings

Successfully produced broadband squeezed vacuum covering 10Hz to 10kHz

Achieved stable long-term control of the squeezed field

Demonstrated sensitivity improvement in a Michelson interferometer

Abstract

We propose and demonstrate a coherent control scheme for stable phase locking of squeezed vacuum fields. We focus on sideband fields at frequencies from 10Hz to 10kHz which is a frequency regime of particular interest in gravitational wave detection and for which conventional control schemes have failed so far. A vacuum field with broadband squeezing covering this entire band was produced using optical parametric oscillation and characterized with balanced homodyne detection. The system was stably controlled over long periods utilizing two coherent but frequency shifted control fields. In order to demonstrate the performance of our setup the squeezed field was used for a nonclassical sensitivity improvement of a Michelson interferometer at audio frequencies.