Hybrid SU(1,1) Interferometry Enables Sub-Shot-Noise Sensitivity in Optomechanical Systems

Precision measurement relies on interferometry, but achieving sensitivity beyond classical limits presents a significant challenge, particularly when dealing with noisy systems. Chao Meng, Emil Zeuthen, and Polina R. Sharapova, working at the Niels Bohr Institute and Paderborn University respectively, now demonstrate a new approach to this problem by combining the principles of SU(1,1) interferometry with optomechanical systems. Their work introduces a hybrid interferometer where mechanical motion forms one component, enabling sub-shot-noise sensitivity without requiring initial squeezing of light, and importantly, offering resilience to signal loss. This innovative design overcomes limitations of traditional methods and promises substantial improvements in the accuracy of precision measurements across a range of applications, paving the way for more sensitive detection of subtle physical phenomena.

entanglement. Scientists propose a hybrid implementation in optomechanics where one “arm” of an interferometer is a mechanical mode undergoing two consecutive, mode-matched interactions with a traveling optical field, constituting the other arm. This engineered interaction allows for sub-shot-noise phase detection, even with mechanical thermal noise and optical losses, advancing precision interferometry in hybrid systems. Interferometry underpins applications from sensing and imaging to fundamental tests of physics, and optomechanical interferometers have already enabled detections of gravitational waves and preparation of quantum states.

Squeezed States Enhance Phase Measurement Precision

This document details a comprehensive theoretical analysis of SU(1,1) interferometry and phase sensing within an optomechanical system. The research focuses on utilizing squeezed states of light to surpass the standard quantum limit in phase sensing. The system employs an optomechanical cavity, where light interacts with mechanical motion, to generate and manipulate these squeezed states. The goal is to measure small phase shifts with the highest possible precision, with applications in gravitational wave detection, precision metrology, and fundamental physics. The analysis meticulously models the system, calculating transfer functions and correlations to describe how the input signal, the phase shift, is processed, demonstrating how the optomechanical interaction generates squeezed states essential for beating the standard quantum limit.

A significant portion of the analysis focuses on noise sources that limit system performance, including thermal noise in the mechanical element, optical loss, and technical noise. The document details how these noise sources degrade squeezing and increase uncertainty in phase estimation, demonstrating how to optimize system parameters, such as squeezing strength and cavity coupling, to minimize phase sensitivity and approach, and even surpass, the standard quantum limit. The research quantifies the impact of each noise source and identifies the dominant limitations, providing a detailed and rigorous theoretical model and practical guidance for designing and optimizing optomechanical systems for high-precision phase sensing.

Entangled Light and Sound Enhance Precision Measurement

Scientists have achieved a groundbreaking implementation of sub-shot-noise interferometry using an optomechanical system, demonstrating a novel approach to precision measurement. The research centers on an interferometer where traditional beam splitters are replaced by two-mode squeezers, enabling enhanced sensitivity and robustness against signal loss. This innovative design utilizes a hybrid system where light interacts with a mechanical mode, creating entangled photons and phonons at specific frequencies. Experiments reveal the generation of correlated photons and phonons driven by a laser, with the team carefully shaping drive-pulse envelopes to achieve highly sensitive detection of signal phase through photon counting measurements.

Measurements confirm that the interaction strength governs the entanglement between photons and phonons. The researchers developed equations to model the system’s dynamics, accounting for coupling to external optical modes and the mechanical environment. Data shows that the mechanical damping rate is small enough to allow for negligible intrinsic mechanical damping, demonstrating the ability to achieve ideal two-mode squeezing under conditions of minimal thermal decoherence. The team established that the duration of the squeezing sequence is much shorter than the decoherence time, ensuring minimal thermal noise, and achieved mode matching between concatenated interactions, with an internal efficiency quantified by a specific parameter. The results demonstrate a significant advancement in precision interferometry, paving the way for highly sensitive sensors and measurements in diverse applications.

Beyond Standard Quantum Limit Measurements Achieved

This research demonstrates a new approach to precision measurement using an optomechanical SU(1,1) interferometer, a system where light and mechanical motion are combined to enhance sensitivity. Scientists have successfully proposed and modeled a hybrid interferometer, replacing traditional beam splitters with engineered interactions between light and a mechanical oscillator. This configuration enables sensitivity beyond the standard quantum limit, even in the presence of thermal noise and imperfections, with the team’s analysis revealing that careful control of experimental parameters is crucial for achieving optimal performance. Importantly, the proposed scheme maintains its enhanced sensitivity even under realistic operating conditions, such as at room temperature, suggesting practical applicability. While the work focuses on an optomechanical system, the methodology developed is broadly applicable to other hybrid quantum systems, expanding the potential for utilizing multimode SU(1,1) interferometers. The authors acknowledge that maintaining precise control over system parameters is essential for realizing the predicted performance gains, with future work likely focusing on experimental realization of this scheme and further exploration of its capabilities in diverse quantum sensing applications.