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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Enhanced resolution in lossy phase estimation by optical parametric amplification

Nicolò Spagnolo, Chiara Vitelli, Lorenzo Toffoli, F. De Martini, Fabio Sciarrino

Published Apr 30, 2011• 0 citations
Publisher

Abstract

In the optical sensing context one of the main challenge is to design and implement novel techniques of sensing optimized to work in a lossy scenario, in which effects of environmental disturbances can destroy the benefits deriving from the adoption of quantum resources. Here we describe the experimental implementation of a protocol based on the process of optical parametric amplification to boost interferometry sensitivity in the presence of losses in a minimally invasive scenario. By performing the amplification process on a microscopic probe after the interaction with the sample, we can beat the losses detrimental effect on the phase measurement which affects the single photon state after its interaction with the sample, and thus improve the achievable sensitivity.

DOI
10.1117/12.886457

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In the optical sensing context one of the main challenge is to design and implement novel techniques of sensing optimized to work in a lossy scenario, in which effects of environmental disturbances can destroy the benefits deriving from the adoption of quantum resources. Here we describe the experimental implementation of a protocol based on the process of optical parametric amplification to boost interferometry sensitivity in the presence of losses in a minimally invasive scenario. By performing the amplification process on a microscopic probe after the interaction with the sample, we can beat the losses detrimental effect on the phase measurement which affects the single photon state after its interaction with the sample, and thus improve the achievable sensitivity.
In the quantum sensing context most of the efforts to design novel quantum techniques of sensing have been constrained to idealized, noise-free scenarios, in which effects of environmental disturbances could be neglected. In this work, we propose to exploit optical parametric amplification to boost interferometry sensitivity in the presence of losses in a minimally invasive scenario. By performing the amplification process on the microscopic probe after the interaction with the sample, we can beat the losses' detrimental effect on the phase measurement which affects the single-photon state after its interaction with the sample, and thus improve the achievable sensitivity.
The aim of quantum sensing is to develop quantum methods to extract the maximum amount of information from a system with minimal disturbance upon it. Indeed, the possibility of performing precision measurements by adopting quantum resources can increase the achievable precision going beyond the semiclassical regime of operation. However the quantum states suitable for quantum metrology protocols, result extremely fragile under losses and decoherence, unavoidable in experimental implementations, destroying completely quantum benefits. This scenario puts the beating of realistic, noisy environments as the main challenge in developing quantum sensing.
Optical interferometry is a cornerstone technique for precise phase measurements across various fields. In many applications, for example, biological imaging, it often necessitates stringent limits on light intensity to prevent adverse effects on light-sensitive samples, a condition known as dose-limited regimes. Maximizing the precision per dose is therefore crucial. In quantum metrology, quantum correlations enable high precision in phase estimation while adhering to dose constraints. Nevertheless, photon loss, including absorption by a sample, substantially diminishes the benefits of quantum enhancement in interferometry. In this work, we experimentally investigate a dose-efficient approach to quantum phase estimation using sequential strategies in the presence of loss. Performance of sequential strategies with and without control is evaluated through quantum Fisher information (QFI) per dose. Experimental results show that both sequential strategies exceed the classical limit and outperform the parallel strategy using unbalanced N00N states. Notably, the control-enhanced sequential strategy attains superior QFI per dose, approaching the quantum limit. These results highlight the promise of sequential strategy for imaging and sensing in resource-constrained scenarios, marking a significant step toward practical and efficient quantum metrology in lossy environments.
The sensitivity in optical interferometry is strongly affected by losses during the signal propagation or at the detection stage. The optimal quantum states of the probing signals in the presence of loss were recently found. However, in many cases of practical interest, their associated accuracy is worse than the one obtainable without employing quantum resources (e.g., entanglement and squeezing) but neglecting the detector's loss. Here, we detail an experiment that can reach the latter even in the presence of imperfect detectors: it employs a phase-sensitive amplification of the signals after the phase sensing, before the detection. We experimentally demonstrated the feasibility of a phase estimation experiment able to reach its optimal working regime. Since our method uses coherent states as input signals, it is a practical technique that can be used for high-sensitivity interferometry and, in contrast to the optimal strategies, does not require one to have an exact characterization of the loss beforehand.