Squeezed States Enhance Gravimetry Beyond the Shot-noise Limit, Achieving Optimal Sensitivity with Phase Adjustment

Gravimetry, the precise measurement of gravitational acceleration, stands to benefit from innovative approaches to enhance detection sensitivity, and a team led by Oziel R. de Araujo and Lucas S. Marinho from Universidade Federal do Piauí are pioneering new techniques using the principles of quantum mechanics. Their research investigates how ‘squeezed’ states of light, carefully manipulated to reduce quantum noise, can improve the accuracy of gravimetric measurements, with contributions from Jonas F. G. Santos and Carlos H. S. Vieira. The team demonstrates that simply increasing the intensity of squeezed light is not enough to surpass fundamental limits in precision, but that carefully controlling the phase of the squeezing, combined with specific measurement strategies, unlocks significant improvements. These findings are crucial for advancing experimental gravimetry, potentially leading to more sensitive instruments for applications ranging from geological surveys to fundamental tests of gravity.

Squeezed states redistribute quantum uncertainty, a technique that can be exploited to improve measurements sensitive to specific properties. The research focuses on the quantum Fisher information, a theoretical limit on measurement precision, and compares it to classical approaches. By analyzing different measurement strategies, scientists aim to reach this theoretical limit, revealing that projective momentum measurements, combined with carefully controlled squeezing, are the most effective way to extract information about gravitational acceleration. The team discovered that the optimal squeezing direction changes over time, meaning the squeezing parameters must be dynamically adjusted during the measurement to maximize precision. This research has practical implications for the design of high-precision sensors used in gravitational wave detection, geodesy, inertial sensing, and fundamental tests of gravity.

Correlated States Enhance Gravitational Acceleration Estimation

Scientists investigated how squeezed states of matter can improve the estimation of gravitational acceleration, focusing on the impact of the phase characteristics of these states. They discovered that simply increasing the intensity of squeezing is not always sufficient to surpass the standard quantum limit. To overcome this limitation, the team developed position-momentum correlated input states, leveraging the relationship between these properties to achieve enhanced sensitivity. This involved engineering quantum states where position and momentum are intrinsically linked, allowing for more precise measurements of gravitational acceleration. They then implemented a technique combining projective momentum measurements with a time-dependent adjustment of the squeezing phase, optimizing the measurement process for maximum sensitivity. Through a phase-space formalism, scientists characterized and manipulated the quantum states, demonstrating that optimal sensitivity is attained by carefully tailoring both the correlation between position and momentum and the time evolution of the squeezing phase.

Dynamic Squeezing Enhances Gravity Measurements

This research demonstrates that carefully engineered quantum states, specifically squeezed states of light, can significantly improve the precision of gravitational acceleration measurements. Scientists have shown that the phase of the squeezing, beyond simply its intensity, plays a crucial role in achieving optimal sensitivity. Probes squeezed along one direction in phase space can fail to outperform standard measurements, but by correlating position and momentum and dynamically adjusting the squeezing phase, enhanced precision becomes possible. The team discovered that the best results are obtained by combining projective momentum measurements with a time-dependent adjustment of the squeezing phase, allowing for greater sensitivity than achievable with conventional techniques or probes squeezed in a fixed direction.

Importantly, this improvement in precision does not require additional energy input from the probe state. Analysis reveals that the capacity to estimate gravitational acceleration is independent of its strength, meaning the method is applicable across a range of gravitational fields. The authors acknowledge that the observed enhancements are dependent on specific interaction times and that further investigation is needed to explore the full potential of this approach in realistic experimental settings. Future work could focus on optimizing the time-dependent adjustment of the squeezing phase and exploring the application of these techniques to other precision measurement scenarios.