Quantum Radar: An Engineering Perspective

TL;DR

This review surveys microwave quantum radar, arguing that quantum illumination and microwave entanglement offer sensitivity gains in noisy, lossy environments where classical radar struggles. It surveys devices—JPAs, JPCs, JTWPAs—and transduction schemes (EOM and OE converters) that generate and preserve entanglement across microwave–optical domains, along with atmospheric-channel models and receiver architectures that exploit correlations via digital post-processing. Key contributions include theoretical frameworks for Gaussian correlations, entanglement criteria, and practical designs, plus experimental demonstrations that move quantum radar toward real-world viability under cryogenic-to-room-temperature operation. The findings underscore the potential for quantum radar to surpass classical limits in sensing and to enable broader quantum-tech applications, while highlighting remaining hurdles such as memories, detectors, and integrated interfaces for scalable deployment.

Abstract

Quantum radar has emerged as a promising paradigm that utilizes entanglement and quantum correlations to overcome the limitations of classical detection in noisy and lossy environments. By exploiting microwave entanglement generated from superconducting devices such as Josephson parametric amplifiers, converters, and traveling-wave parametric amplifiers, quantum radar systems can achieve enhanced detection sensitivity, lower error probabilities, and greater robustness against thermal noise and jamming. This review provides a comprehensive overview of the field, beginning with the theoretical foundations of quantum illumination and extending to the generation of entanglement in the microwave regime. We then examine key quantum radar subsystems, including quantum transducers, amplification chains, and receiver architectures, which form the backbone of practical designs. Recent experimental systems are surveyed in the microwave domain, highlighting proof-of-principle demonstrations and their transition from conceptual frameworks to laboratory realizations. Collectively, the progress reviewed here demonstrates that quantum radar is evolving from a theoretical construct to a practical quantum technology capable of extending the performance boundaries of classical radar.

Figures (17)

• Figure 1: Diagram representing the relationship between quantum entanglement and quantum discord. All entangled states lie within the set of discordant states, but discord can exist without entanglement.
• Figure 2: EOM converter; coupling subsystems contain OC, MC, and MR salmanogli2020entanglement.
• Figure 3: Entanglement between cavities modes; $C_s$ and $q_s$ are real under varying parameters: (a) Temperature effect, (b) incident source wavelength effect, (c), and (d) study of the effect of the MR salmanogli2020entanglement.
• Figure 4: Optoelectronic system schematic; $C_s$ and $q_s$ are real under varying parameters: (a) OC mode coupling to MC mode through the photodetector and a Varactor diode, (b) a typical GaAs photodetector responsivity graph newport_biased_detector, (c) Varactor diode capacitance variation vs biased voltage, which is the function of photodetector current junction_tuning_varactor and (d) simulated photocurrent as a function of optical cavity mode incidence wave frequency and amplitude. The optical mode center wavelength is around 808 nm salmanogli2019entanglement.
• Figure 5: Temperature effect on entanglement between: (a) $a_c$ and $c_{\omega}$, (b) $a_c$ and $c_b$ for $\mu_c = 0.0002$ and $D_{td} = 20$ m $\kappa_{atm} = 2 \times10^{-6}$ 1/m, and $\kappa_t = 18.2$ 1/m salmanogli2021entanglement.