Quantum positioning is based on quantum signals to realize target detection. However, the quantum signal is inevitably interfered by the scattering environment during transmission, and the interference changes with the time and transmission path from each Light Source (LS) to the target. It is thereby needed to build up a good strategy for finding the set of the most useful LSs for quantum positioning. Therefore, we propose an entangled quantum positioning method based on the Scattering Free Path (SFP) model. Firstly, the light quantum transmission model is established to describe the change of photon number and transmission distance of the photon. Secondly, the SFP for each LS and each time group is constructed based on environment information and coincidence counting. Thirdly, the SFP sequence for each LS is resampled, and the relative SFP error under each time group is calculated. Finally, the LSs corresponding to the minimum relative errors are selected for each time group to estimate the position coordinate of the target.
Quantum positioning is based on quantum signals to realize target detection. However, the quantum signal is inevitably interfered by the scattering environment during transmission, and the interference changes with the time and transmission path from each Light Source (LS) to the target. It is thereby needed to build up a good strategy for finding the set of the most useful LSs for quantum positioning. Therefore, we propose an entangled quantum positioning method based on the Scattering Free Path (SFP) model. Firstly, the light quantum transmission model is established to describe the change of photon number and transmission distance of the photon. Secondly, the SFP for each LS and each time group is constructed based on environment information and coincidence counting. Thirdly, the SFP sequence for each LS is resampled, and the relative SFP error under each time group is calculated. Finally, the LSs corresponding to the minimum relative errors are selected for each time group to estimate the position coordinate of the target.
As one of the state-of-the-art technologies currently being studied in the field of target positioning, the entangled light quantum-based passive target positioning method uses quantum entangled states to detect and localize the target, thus providing highly-accurate and anti-interference positioning services. The conventional methods seldom consider the problem that maybe a pseudo-target is detected when there is actually no target due to the interference of particles, scatterers, and noise photons during light quantum transmission. To address this problem, this paper proposes a new passive target positioning method on uncertain detection path based on entangled light quantum. Specifically, first of all, by converting the continuous light energy into the discrete photon number, the photon return rate is used to calculate the number of arrival photons based on the counting characteristics of the single photon detector. Second, the detection probabilities of signal, idler, and noise photons are calculated to obtain the coincidence probability at the receiver. Third, according to the coincidence count value of the entangled light time pulse sequence, the Constant False Alarm Rate (CFAR) detection model is established, and the corresponding detection threshold is adaptively adjusted with the change of the background noise to achieve highly-sensitive target detection. Finally, the relative error for each light source is considered to select the optimal light sources with the smallest relative distance errors for target positioning. In addition, the results show that the detection probability of the proposed method is over 95% with the false alarm probability 0.05, the positioning error is centimeter-level, and the confidence probability within 2.60 cm can reach 92%.
Aiming at the problem that the dynamic change of the scattering environment affects the propagation distance estimation performance by different light sources, resulting in low positioning accuracy and poor robustness, a light quantum positioning method based on integrated coincidence counting and adaptive light source selection is proposed. Specifically, the method considers the dynamic changes of the scattering environment to group the entangled light time pulse sequences, calculates the signal propagation distance of each light source under each group based on the coincidence count, and takes the relative error of each light source under each group as the basis to dynamically select different light sources for positioning. The experimental results show that the proposed method has higher positioning accuracy and stronger positioning robustness.
Three-dimensional (3D) imaging in low-light environments has broad application prospects. High-quality 3D imaging requires obtaining both the depth and reflectivity information of the target. With the rapid development of Quantum Information Technology (QIT), Quantum Imaging (QI) provides a new approach to achieve high-quality 3D imaging. However, traditional QI methods are limited to Two-dimensional (2D) imaging and cannot accurately extract the depth information from the target. These methods also suffer from insufficient precision in reflectivity calculations. Therefore, we introduce a novel quantum 3D imaging and reflectivity estimation method based on entangled photons. Specifically, we first utilize the spatiotemporal correlation characteristics of entangled photon pairs combined with coincidence measurement technology to accurately determine target depth. Second, we analyze the distribution of entangled photon numbers during free-space transmission to construct a photon-based detection probability model. Third, we use this model to derive the probability density function of coincidence counts. Finally, we estimate the surface reflectivity information through statistical analysis of coincidence counting. Experimental results demonstrate that the proposed method can accurately reconstruct both depth and reflectivity profiles of the target in low-light environments. These findings validate the effectiveness of our method and highlight the potential of quantum 3D imaging for target detection in low-light environments.
The entangled quantum radar applies the quantum information technology to the radar sensing network and detection system. The dynamic particle changes and optical attenuation caused by complex atmospheric environments will severely limit the traditional radar performance. Due to entanglement characteristics, the entangled optical quantum radar has better anti-stealth interference ability, stronger anti-turbulence properties, and higher spatial resolution which makes it promising in complex and high-attenuation environments. In addition, quantum radar based on the entangled light source can overcome the limitations of low imaging resolution and low confidentiality in traditional target detection. Therefore, high-precision positioning and high-resolution imaging are the research focus of the quantum radar sensing network. Based on this, we first design and optimize an optical path structure of the quantum entangled light source to obtain higher brightness entangled source which is suitable for complex atmospheric environments. Second, in response to the problem of low positioning accuracy in the traditional quantum radar, we design a new positioning optical path and propose a novel entangled optical quantum positioning method based on the photon scattering model. Third, to address the problems of low resolution and slow speed in traditional quantum radar imaging, we propose a new entangled light quantum imaging method based on two-phase coincidence counting. Finally, we conduct extensive experiments to evaluate the effectiveness of the proposed method in complex atmospheric environments and further provide possibilities for the entangled light source quantum radar sensing network.
Microwaves exhibit superior performance in free-space transmission compared to optical waves, primarily due to their ability to penetrate fog and experience lower losses in the Earth's atmosphere. Based on microwave-optical entanglement prepared by nano-cavity electro-opto-mechanic converters, we propose a scheme of a quantum positioning system using the distance-based positioning method. Principles of microwave-optical entanglement preparation and our QPS scheme are introduced in detail. The entanglement feature, system stability and positioning feature of the scheme are analyzed after simulations. Furthermore, we delve into the impact of key parameters, such as transmissivity and photon conversion efficiency, on positioning. Notably, the entanglement degrees for both microwave-optic entanglement at the transmitter and optic-optic entanglement at the receiver surpass one, affirming the efficiency of the scheme in preparing and maintaining entanglement. When transmissivity in beam-splitter models of both ground stations equals 0.5, our scheme achieves a minimal positioning error of 6.4×10-7m2 under ideal conditions. Additionally, we map out traces of a plane through continuous positioning using our scheme. These results demonstrate the theoretical efficiency and robustness of our proposed approach.
Entangled photon quantum imaging technology has become very promising for marine imaging due to its high resolution, anti-turbulence, and anti-interference properties. The turbulence and optical attenuation caused by oceanic water would impose severe limitations on conventional imaging equipment. Quantum imaging based on entangled light sources could make it possible to overcome the constraints of low imaging resolution, large maritime environmental impact and low confidentiality in traditional underwater target imaging. Hence, the recent technological developments in terms of quantum imaging in free space motivate our investigation into high-resolution quantum imaging based on spatially correlated properties of entangled photon pairs in a marine environment. Moreover we propose and design an innovative underwater quantum imaging optical path for experimental verification. We conduct extensive experiments to assess the effectiveness of our proposed quantum imaging approach in marine environments. In order to solve the problem of the slow quantum imaging process, we propose an innovative compressive sensing reconstruction algorithm. Experiments show that the compressive sensing method could be utilized to reduce the imaging time. Finally, we propose an underwater quantum target identification method based on deep learning, further providing the possibility for underwater quantum target identification of entangled light sources.