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arXiv:2303.05218 · Optics Express

Quantum illumination using polarization-path entangled single photons for low reflectivity object detection in a noisy background

K. Muhammed Shafi, A. Padhye, C. M. Chandrashekar

Published Aug 16, 2023• 9 citations
arXivHTMLPDF

Abstract

Detecting object with low reflectivity embedded within a noisy background is a challenging task. Quantum correlations between pairs of quantum states of light, though are highly sensitive to background noise and losses, offer advantages over traditional illumination methods. Instead of using correlated photon pairs which are sensitive, we experimentally demonstrate the advantage of using heralded single-photons entangled in polarization and path degree of freedom for quantum illumination. In the study, the object of different reflectivity is placed along the path of the signal in a variable thermal background before taking the joint measurements and calculating the quantum correlations. We show the significant advantage of using non-interferometric measurements along the multiple paths for single photon to isolate the signal from the background noise and outperform in detecting and ranging the low reflectivity objects even when the signal-to-noise ratio is as low as 0.03. Decrease in visibility of polarization along the signal path also results in similar observations. This will have direct relevance to the development of single-photon based quantum LiDAR and quantum imaging.

DOI
10.1364/oe.496776

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Detecting object with low reflectivity embedded within a noisy background is a challenging task. Quantum correlations between pairs of quantum states of light, though are highly sensitive to background noise and losses, offer advantages over traditional illumination methods. Instead of using correlated photon pairs which are sensitive, we experimentally demonstrate the advantage of using heralded single-photons entangled in polarization and path degree of freedom for quantum illumination. In the study, the object of different reflectivity is placed along the path of the signal in a variable thermal background before taking the joint measurements and calculating the quantum correlations. We show the significant advantage of using non-interferometric measurements along the multiple paths for single photon to isolate the signal from the background noise and outperform in detecting and ranging the low reflectivity objects even when the signal-to-noise ratio is as low as 0.03. Decrease in visibility of polarization along the signal path also results in similar observations. This will have direct relevance to the development of single-photon based quantum LiDAR and quantum imaging.
Entangled light sources for illuminating objects offer advantages over conventional illumination methods by enhancing the detection sensitivity of reflecting objects. The core of the quantum advantage lies in effectively exploiting quantum correlations to isolate noise and detect objects with low reflectivity. This work experimentally demonstrates the benefits of using polarization-entangled photon pairs for quantum illumination and shows that the quantum correlation measure, using CHSH value and normalized CHSH value, is robust against losses, noise, and depolarization. We report the detection of objects with reflectivity (η) as low as 0.05 and an object submerged in noise with a signal-to-noise ratio of 0.003 using quantum correlation and residual quantum correlation measures, surpassing previous results. Additionally, we demonstrate that the normalized CHSH value aids in estimating the reflectivity of the detected object. Furthermore, we analyze the robustness of the correlation measure under photon attenuation in atmospheric conditions to show the practical feasibility of real-time applications.
Abstract Imaging, detection and ranging of objects in the presence of significant background noise is a fundamental challenge in optical sensing. Overcoming the limitations imposed in conventional methods, quantum light sources show higher resistance against noise in a time-correlation-based quantum illumination. Here, we introduce the advantage of using not only time correlations but also polarization correlations in photon pairs in the detection of an object that is embedded in a noisy background. In this direction, a time- and polarization-correlated photon pair source using the spontaneous parametric down-conversion process is exploited. We found that the joint measurement of correlated pairs allows distinguishing the signal from the noise photons and that leads to an improved signal-to-noise ratio. Our comparative study revealed that using polarization correlations in addition to time correlations provides improved noise rejection. Furthermore, we show that polarization correlation allows undoing the detector limitation where high background often leads to detector saturation.
Modern optical sensing systems, particularly LiDAR, play a central role in remote sensing and precision measurement. However, they face fundamental limits when operating in noisy and highly lossy environments. Quantum illumination has emerged as a promising approach to overcome these challenges by exploiting quantum correlations. This work presents the system design and performance analysis of a quantum illumination based LiDAR architecture operating at optical frequencies. The proposed system exploits entangled photon pairs generated through spontaneous parametric down conversion to enhance detection sensitivity and robustness under weak return conditions. A complete hardware oriented framework is developed, including the entanglement source, nonlinear crystal configuration, pump laser requirements, optical propagation path, quantum memory implementation, and a detection architecture based on quantum erasure Hong-Ou-Mandel interference. Practical realization using superconducting nanowire single photon detectors is discussed to enable high efficiency and low noise photon measurement. In addition, a system level link budget and noise analysis evaluates the impact of optical losses, atmospheric attenuation, turbulence, and detector imperfections on overall performance. The study highlights how quantum correlations can improve signal to noise performance compared with classical illumination strategies, particularly in low reflectivity and high background scenarios. The presented architecture provides a realistic framework for implementing quantum LiDAR systems and supports the development of next generation long range sensing technologies.
Quantum illumination is one of the most basic ways to realize the quantum radar for detection of low-reflectivity targets embedded in a thermal-noise bath. It preserves a strong advantage over the classical counterparts even though its fragile quantum entanglement is completely destroyed by a large amount of noise and losses. In this paper, we describe and analyze a discrete-variable quantum illumination system with ancillary degrees of freedom of entangled photon pairs. Comparing the error probability bound, i.e., the quantum Chernoff bound, we identify that this system indeed offers higher accuracy than the single-photon illumination and quantum illumination with single degree of freedom of entangled photon pairs. Furthermore, the utilization of ancillary degrees of freedom exponentially enhances signal-to-noise ratio over quantum illumination without ancillary degrees of freedom. It means that this system reduces the necessary amount of signal photons to accurately determine whether the object is present or absent in the target region, which is absolutely crucial to the stealthiness of the radar system.
Abstract Most quantum systems that are used for generating entanglement and for practical applications are not isolated from the environment, and are hence susceptible to noise. Entanglement in more than one degree of freedom between two systems, known as hyperentanglement, is known to have certain advantages, including robustness against noise over conventional entangled states. Quantum illumination, imaging and communication schemes that involve sending one photon from a pair of entangled photons and retaining the other photon usually involve exposing only the signal photon to environmental noise. The disruptive nature of noise degrades entanglement and other correlations which are crucial for many of these applications. In this paper, we study the advantages of using photon pairs in certain path-polarization hyperentangled states in a noisy interaction where photons in only one of the paths are affected by noise. We model such noise and study the effect of noise on the correlations present in the hyperentangled photons. Three different methods, entanglement negativity, entanglement witnesses and Bell nonlocality are used to show the resilience of path-polarization hyperentangled probe state against noise.