Quantum physics has brought enhanced capability in various sensing applications. Despite challenges from noise and loss in the radio-frequency (RF) domain, [Phys. Rev. Lett. 124, 150502 (2020)] demonstrates a route for enhanced RF-receiver empowered by quantum squeezing and entanglement. In this work, we further explore the quantum advantage of imaging in the weak coupling scenario of the RF-photonic receiver. The proposed imaging receiver applies transducer to upconvert the RF signal to optical to enable high-efficiency connection via low-loss fiber networks. The efficient connection therefore increases the synthetic aperture and improves the resolution of the distributed imaging system. To overcome the challenge from low transduction efficiency in existing devices limited by weak photon interaction, we propose the use of squeezed-state optical sources to suppress the noise. We numerically evaluate the quantum advantage in synthetic aperture radar imaging, where the images are generated from the standard resolution test chart via a Gaussian point spread function with added Gaussian noise. We apply the Wiener filter on the images to restore the objects and find that stronger squeezing significantly improves the quality of the restored image. Our findings push quantum squeezing advantage to real-world applications.
Quantum physics has brought enhanced capability in various sensing applications. Despite challenges from noise and loss in the radio-frequency (RF) domain, [Phys. Rev. Lett. 124, 150502 (2020)] demonstrates a route for enhanced RF-receiver empowered by quantum squeezing and entanglement. In this work, we further explore the quantum advantage of imaging in the weak coupling scenario of the RF-photonic receiver. The proposed imaging receiver applies transducer to upconvert the RF signal to optical to enable high-efficiency connection via low-loss fiber networks. The efficient connection therefore increases the synthetic aperture and improves the resolution of the distributed imaging system. To overcome the challenge from low transduction efficiency in existing devices limited by weak photon interaction, we propose the use of squeezed-state optical sources to suppress the noise. We numerically evaluate the quantum advantage in synthetic aperture radar imaging, where the images are generated from the standard resolution test chart via a Gaussian point spread function with added Gaussian noise. We apply the Wiener filter on the images to restore the objects and find that stronger squeezing significantly improves the quality of the restored image. Our findings push quantum squeezing advantage to real-world applications.
We demonstrate a resolution enhancement scheme of radio-frequency signals by tailoring a phase-squeezed state.The echo radio-frequency signals collected by photonic radar give rise to displacements in the phase quadrature of a probe laser and are estimated by the balanced homodyne detector.In contrast to the conventional coherent state, the noise variances for radio-frequency estimation with a squeezed state are reduced by approximately 6.9 dB.According to the Rayleigh criterion that defines the resolution limit, the minimum resolvable displacement Δa with a squeezed state is reduced to 45% compared to that with a coherent state, demonstrating the quantum advantage.The squeezing-enhanced technique has extensive applications for multitarget recognition and tracking in contemporary photonic radar systems.
Quantum imaging utilizes the correlation of photons to enhance the security, covertness, and noise resilience of optical imaging. Despite recent advances, developing a quantum imaging system with long-distance and strong noise resilience remains challenging. Here, we present an experimental demonstration of high-performance quantum imaging at telecom band with enhanced noise resilience. We use a fiber-integrated quantum light source via cascaded second-order nonlinear processes to generate high-quality correlated/entangled photon pairs at telecom band and a fiber-coupled confocal optical system to effectively suppress the background noise and improve the collection efficiency of echo signal photons by optimizing its bandwidth and aperture. In our demonstration, the quantum imaging with correlated/entangled photon pairs or heralded single photons is achieved at a distance of 11 m under indoor illumination. When the detected environment noise is 33 dB stronger than the signal photons, corresponding to a coincidence-to-accidental coincidence ratio of 1.7 ± 0.1, an imaging contrast of 0.23 ± 0.09 is achieved, which is 46 times higher than single-photon imaging without correlation. The results will open venues for the development of practical quantum imaging techniques.
As the main branch of microwave photonics, radio-over-fiber technology provides high bandwidth, low-loss, and long-distance propagation capability, facilitating wide applications ranging from telecommunication to wireless networks. With ultrashort pulses as the optical carrier, a large capacity is further endowed. However, the wide bandwidth of ultrashort pulses results in the severe vulnerability of high-frequency radio frequency (RF) signals to fiber dispersion. With a time-energy entangled biphoton source as the optical carrier combined with the single-photon detection technique, a quantum microwave photonics method in radio-over-fiber systems is proposed and demonstrated experimentally. The results show that it not only realizes unprecedented nonlocal RF signal modulation with strong resistance to the dispersion but also provides an alternative mechanism to distill the RF signal out from the dispersion effectively. Furthermore, the spurious-free dynamic ranges of the nonlocally modulated and distilled RF signals have been significantly improved. With the ultra-weak detection and the high-speed processing advantages endowed by the low-timing-jitter single-photon detection, the quantum microwave photonics method opens new possibilities in modern communication and networks.
As a combination of laser technology and modern photoelectric detection technology, lidar (laser radar) has notable advantages compared with traditional radar such as high resolution, strong anti-interference ability, and good low-altitude detection performance. However, with continuous application in aerospace, military, artificial intelligence and other fields, lidar has reached the limits of classical physics and can’t meet the requirements in detection, measurement and imaging. In order to break the bottleneck, worldwide researchers have developed a new type of radar-quantum lidar, which is based on the combination of traditional radar technology and quantum information technology. Its main principle is to get imaging through squeezed light that is below the noise limit of classical physics and then manipulated by the quantum state to achieve imaging with higher quality. Quantum lidar in the paper injects quantum squeezed light to receiver end and uses quantum phase-sensitive amplifier technology to compensate the photon loss that caused by insufficient quantum power to further improve resolution. In the squeezed light, the generation of quantum squeezed light and detection theory are studied, the resonant cavity locking principle and balanced homodyne detection principle are analyzed, and a mode cleaner with narrow line width is designed to improve beam transverse mode quality of laser and filter high frequency noise. In order to reduce quantum noise and improve resolution, quantum lidar imaging system is developed and the theoretically derivation and numerical simulation results show that the resolution of quantum lidar imaging is 1.71 times higher than that of lidar imaging.
Microwave quantum illumination (QI) represents a paradigm shift in low-power wireless radar detection, leveraging entanglement between signal and idler microwave photons to achieve detection performance exceeding classical limits by up to 6 dB in error exponent, particularly in high-noise environments where traditional coherent radars falter. This comprehensive survey delineates the theoretical foundations and practical protocols of microwave QI, beginning with two-mode squeezed vacuum state generation using Josephson parametric amplifiers in cryogenic setups, which produce highly correlated photon pairs resilient to channel decoherence. Receiver architectures, including optical parametric amplifier-single-photon avalanche diode (OPA-SPADE) systems with sum-frequency generation for joint measurements and digital phase-conjugation for computational correlation recovery, enable efficient extraction of quantum discord even after significant atmospheric loss or low target reflectivity (under 1%).Performance analyses under realistic thermal noise models ( ) and -loss channels confirm sustained quantum advantages via the quantum Chernoff exponent , validated by ray-tracing simulations showing doubled detection range at fixed power and lab experiments at 10 GHz carriers detecting weak reflectors amid 100 K noise. Low-power optimizations such as adaptive entanglement tuning, chirped pulse shaping, and neural network-aided parameter selection yield 50% energy reductions without sacrificing fidelity, making QI viable for battery-limited platforms. Applications encompass short-range automotive/UAV radar for fog-penetrating obstacle avoidance, non-invasive biomedical subsurface imaging with safe radiation levels, covert perimeter security against jamming, and seamless integration into 6G networks via joint communication-sensing waveforms at mm Wave/THz bands. The paper identifies key challenges including multi-target scalability, real-time gigascale processing, and quantum RF interface standardization, proposing hybrid quantum-classical frameworks and entanglement-swapped sensor arrays as pathways to deployment. This work bridges quantum optics with RF engineering, equipping researchers with blueprints for prototyping transformative quantum-enhanced wireless sensing systems.
Many quantum radars currently studied in the literature use a phenomenon called entanglement to address the problem of distinguishing signal from noise, which is one of the most important problems faced by any radar. Until recently, entanglement-based quantum radars at radio frequencies existed only in theory; their practicality was very much in doubt. The situation has changed with a recent experimental implementation of all the necessary components of a quantum two-mode squeezing (QTMS) radar, which operates at microwave frequencies and can be described as a quantum range finder. In this article, we lay out the exact problem solved by this prototype, namely quantum noise, and explain how entanglement can overcome the existence of this noise. By analyzing the QTMS radar prototype, we point out a technological route to an entanglement-based quantum radar that can, in principle, perform all tasks that radars can and must do, such as array processing, clutter suppression, and image processing (including synthetic aperture radar and inverse synthetic aperture radar).