Analysis of quantum-based methods for improved gravimetric sensing has demonstrated that photon entanglement can provide an additional source of target-state information beyond what is possible using purely classical sensing techniques. In this paper we propose a quantum-based system for large-scale space-based detection of small near-earth objects (NEOs). The objective of the system is to measure extremely small deviations in the background gravitational field within a defined surveillance region to identify potentially dangerous NEO intrusions as early as possible. The system is composed of a set of widely-separated line-of-sight emitter-receiver pairs that exchange entangled photons so that the signature of a moving object can be discerned from subtle gravitation-induced spin effects. The key advantage of the system is that detection does not require direct illumination of the target. A potentially more important practical advantage is that the system can be implemented using relatively simple interferometric measurements.
Analysis of quantum-based methods for improved gravimetric sensing has demonstrated that photon entanglement can provide an additional source of target-state information beyond what is possible using purely classical sensing techniques. In this paper we propose a quantum-based system for large-scale space-based detection of small near-earth objects (NEOs). The objective of the system is to measure extremely small deviations in the background gravitational field within a defined surveillance region to identify potentially dangerous NEO intrusions as early as possible. The system is composed of a set of widely-separated line-of-sight emitter-receiver pairs that exchange entangled photons so that the signature of a moving object can be discerned from subtle gravitation-induced spin effects. The key advantage of the system is that detection does not require direct illumination of the target. A potentially more important practical advantage is that the system can be implemented using relatively simple interferometric measurements.
Quantum radar systems leverage entangled photon pairs to detect and identify targets in noisy or cluttered environments with sensitivity beyond classical limits. By transmitting one photon of an entangled pair toward a distant object while retaining its partner locally, the system exploits quantum correlations to improve signal discrimination, reduce noise susceptibility, and enhance detection probability. This paper outlines the physical principles, operational architecture, and performance advantages of entanglement‑based illumination, providing a clear foundation for future quantum‑enhanced sensing technologies.(If you want it shorter, longer, or more formal, tap: shorter paragraph, longer paragraph, more formal)
The goal of optical target detection is to identify the presence or absence of a target object by using light or photons as the transmitter. This technique offers significant advantages, such as high resolution and precise directionality, and plays a key role in applications like LiDAR. One of the critical performance metrics in optical target detection is noise resilience─specifically, the system’s ability to distinguish reflected signals from crosstalk or jamming sources with similar optical properties. Traditionally, this challenge has been addressed through classical information processing or standard optical filtering methods. However, a new approach to improving noise resilience has recently captured the attention of numerous researchers: harnessing the unique properties of quantum light sources. These sources offer performance enhancements that are challenging or even impossible to achieve with conventional coherent optical sources. In this perspective, we examine the performance and limitations of this emerging method, including challenges related to receiver complexity and power scaling. We also explore potential strategies to overcome these limitations, highlighting the practical advantages these approaches could offer.
The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent superpositions and quantum correlations, to increase measurement precision. Here we experimentally investigate a scheme for quantum target detection based on linear optical measurement devices, when the object is immersed in unpolarized background light. By comparing the quantum (polarization-entangled photon pairs) and the classical (separable polarization states) strategies, we found that the quantum strategy provides us an improvement over the classical one in our experiment when the signal-to-noise ratio is greater than 1/40, or about 16 dB of noise. This is in constrast to quantum target detection considering nonlinear optical detection schemes, which have shown resilience to extreme amounts of noise. A theoretical model is developed which shows that, in this linear-optics context, the quantum strategy suffers from the contribution of multiple background photons. This effect does not appear in our classical scheme. By improving the two-photon detection electronics, it should be possible to achieve a polarization-based quantum advantage for a signal-to-noise ratio that is close to 1/400 for current technology.
Without light, there would be no sight. Light acts as a probe in various measurement techniques ranging from imaging to spectroscopy, from small scale cantilever displace- ment measurement in atomic force microscopy to large scale mirror motion in interfer- ometry, light detection and ranging (LIDAR) and many other fields. As the light probe intensity rises, it not only allows reducing the background noise effect, but it also aids precision to the measurement by reducing the photon noise (shot-noise) contribution. However, increasing intensity beyond certain threshold level is not always advantageous for ultra sensitive measurements. For example in the detection of gravitational waves, the current power circulating in the large scale interferometers can not be increased further without introducing other noise sources like thermal effects on the mirrors, un- wanted scattered photons, and back action due to radiation pressure. In the imaging of delicate photo sensitive sample, high power can causes cell damage or it may lead to disturb the regular process under investigation, viz. favouring certain biochemical reaction, which do not correspond to natural in vitro behaviour. At low intensity, pho- ton noise is an important concern and quantum states of light with correlated photon fluctuation can ideally represent a fruitful way to build specific measurement strategies to surpass the limitation of standard approach based on classical light sources, offering an avenue of solutions for ultra sensitive measurements. This thesis work focuses on two application of quantum enhanced measurement strate- gies. The first part of the thesis work has been dedicated to the realization of the first wide-field microscope with Sub Shot Noise (SSN) sensitivity. This is based on the ex- ploitation of quantum correlations in the Squeezed Vacuum state. In the second part, the investigations have made on the role of the quantum correlated beams in an unusual interferometric scheme, in which two identical optical interferometers are subject to the same phase fluctuation. The scheme, in the classical regime, has been already imple- mented in a large scale experiment devoted to the search of possible quantum gravity (QG) effects at Fermilab.
Quantum illumination can utilize entangled light to detect the low-reflectivity target that is hidden in a bright thermal background. This technique is applied to the detection of an object in the curved spacetime of the Earth, in order to explore how the curvature of spacetime affects quantum illumination. It is found that the spatial quantum illumination with entangled state transmitter outperforms that with coherent-state transmitter in the near-Earth curved spacetime. Moreover, either the quantum illumination system or the coherent-state system is employed, and gravity can enhance the spacetime target detection by reducing the thermal signal at the receiver. Besides, our model in principle can be applied to microwave quantum illumination and thus provides, to some degree, a theoretical foundation for the upcoming spatial quantum radar technologies.