Generation of squeezed vacuum state in the millihertz frequency band

TL;DR

This paper reports the first direct observation of a squeezed vacuum state at ultra-low frequencies (down to 4 millihertz) with significant noise reduction, advancing quantum measurement for gravitational wave detection.

Contribution

It introduces a novel method to generate and observe squeezed vacuum states at millihertz frequencies, filling a gap in quantum resources for low-frequency gravitational wave observatories.

Findings

Achieved 8 dB quantum noise reduction at 4 millihertz

Demonstrated a multiple noise suppression scheme for ultra-low frequencies

Provided quantum resources for future low-frequency gravitational wave detection

Abstract

The detection of gravitational waves has ushered in a new era of observing the universe. Quantum resource advantages offer significant enhancements to the sensitivity of gravitational wave observatories. While squeezed states for ground-based gravitational wave detection have received marked attention, the generation of squeezed states suitable for mid-to-low-frequency detection has remained unexplored. To address the gap in squeezed state optical fields at ultra-low frequencies, we report on the first direct observation of a squeezed vacuum field until Fourier frequency of 4 millihertz with the quantum noise reduction of up to 8 dB, by the employment of a multiple noise suppression scheme. Our work provides quantum resources for future gravitational wave observatories, facilitating the development of quantum precision measurement.