The sensitivity of laser interferometers is fundamentally limited by the quantum nature of light. Recent theoretical studies have opened a new avenue to enhance their quantum-limited sensitivity by using active parity-time-symmetric and phase-insensitive quantum amplification. These systems can enhance the signal response without introducing excess noise in the ideal case. However, such active systems must be causal, stable, and carefully tuned to be practical and applicable to precision measurements. In this paper, we show that phase-insensitive amplification in laser interferometers can be implemented in a tabletop experiment. The layout consists of two coupled cavities and an active medium comprised of a silicon nitride membrane and an auxiliary pump field. Our design relies on existing membrane and cryogenic technology and can demonstrate three distinct features: (i) the self-stabilized dynamics of the optical system, (ii) quantum enhancement of its sensitivity in the presence of the amplifier, and (iii) optical control of the amplifier gain. These features are needed to enhance the sensitivity of future interferometric gravitational-wave and axion detectors.

• Received 11 October 2022
• Accepted 17 March 2023

DOI:https://doi.org/10.1103/PhysRevA.107.043701

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society