Quantum illumination leverages entanglement to surpass classical target detection, even in high-noise environments. Remarkably, its quantum advantage persists despite entanglement degradation caused by environmental decoherence. A central challenge lies in designing optimal receivers to exploit this advantage, with the correlation-to-displacement (C→D) conversion module emerging as a promising candidate. However, practical implementation remains technically demanding, particularly in realizing a low-noise programmable mode selector. In this work, we propose a scheme for the C→D module that incorporates a cavity-enhanced quantum pulse gate for programmable mode processing, achieving performance close to the theoretical optimum. This integrated framework paves the way for the realization of practical quantum illumination systems.
Quantum illumination leverages entanglement to surpass classical target detection, even in high-noise environments. Remarkably, its quantum advantage persists despite entanglement degradation caused by environmental decoherence. A central challenge lies in designing optimal receivers to exploit this advantage, with the correlation-to-displacement (C→D) conversion module emerging as a promising candidate. However, practical implementation remains technically demanding, particularly in realizing a low-noise programmable mode selector. In this work, we propose a scheme for the C→D module that incorporates a cavity-enhanced quantum pulse gate for programmable mode processing, achieving performance close to the theoretical optimum. This integrated framework paves the way for the realization of practical quantum illumination systems.
Quantum illumination leverages entanglement to surpass classical target detection, even in high-noise environments. Remarkably, its quantum advantage persists despite entanglement degradation caused by environmental decoherence. A central challenge lies in designing optimal receivers to exploit this advantage, with the correlation-to-displacement conversion module emerging as a promising candidate. However, the practical implementation of the conversion module faces technical hurdles, primarily due to the vast number of modes involved. In this work, we address these challenges by proposing a frequency-mode entangled source with matched photon numbers, a heterodyne detection scheme for the returned signals across vast modes, and a cavity-enhanced quantum pulse gate for programmable mode processing. This integrated framework paves the way for the realization of practical quantum illumination systems.
Quantum illumination leverages entanglement to surpass classical target detection, even in high-noise environments. Remarkably, its quantum advantage persists despite entanglement degradation caused by environmental decoherence. A central challenge lies in designing optimal receivers to exploit this advantage, with the correlation-to-displacement conversion module emerging as a promising candidate. However, the practical implementation of the conversion module faces technical hurdles, primarily due to the vast number of modes involved. In this work, we address these challenges by proposing a frequency-mode entangled source with matched photon numbers, a heterodyne detection scheme for the returned signals across vast modes, and a cavity-enhanced quantum pulse gate for programmable mode processing. This integrated framework paves the way for the realization of practical quantum illumination systems.
Entanglement is vulnerable to degradation in a noisy sensing scenario, but surprisingly, the quantum illumination protocol has demonstrated that its advantage can survive. However, designing a measurement system that realizes this advantage is challenging since the information is hidden in the weak correlation embedded in the noise at the receiver side. Recent progress in a correlation-to-displacement conversion module provides a route towards an optimal protocol for practical microwave quantum illumination. In this work, we extend the conversion module to accommodate experimental imperfections that are ubiquitous in microwave systems. To mitigate loss, we propose amplification of the return signals. In the case of ideal amplification, the entire six-decibel error-exponent advantage in target detection error can be maintained. However, in the case of noisy amplification, this advantage is reduced to three decibels. We analyze the quantum advantage under different scenarios with a Kennedy receiver in the final measurement. In the ideal case, the performance still achieves the optimal one over a fairly large range of error probability with only on-off detection. Empowered by photon-number-resolving detectors, the performance is further improved and also analyzed in terms of receiver operating characteristic curves. Our findings pave the way for the development of practical microwave quantum illumination systems.
Quantum illumination utilizes an entanglement-enhanced sensing system to outperform classical illumination in detecting a suspected target, despite the entanglement-breaking loss and noise. However, practical and optimal receiver design to fulfill the quantum advantage has been a long open problem. Recently, Shi et al. [arXiv:2207.06609 (2022)] proposed the correlation-to-displacement $(`\mathrm{C}\phantom{\rule{0.16em}{0ex}}{\phantom{\rule{0.16em}{0ex}}}_{\stackrel{P\vec}{}}\phantom{\rule{0.16em}{0ex}}\mathrm{D}\text{'})$ conversion module to enable an optimal receiver design that greatly reduces the complexity of the previous known optimal receiver [Q. Zhuang, Z. Zhang, and J. H. Shapiro, Phys. Rev. Lett. 118, 040801 (2017)]. There, the analyses of the conversion module assume an ideal target with a known reflectivity and a fixed return phase. In practical applications, however, targets often induce a random return phase; moreover, their reflectivities can have fluctuations obeying a Rayleigh distribution. In this paper, we extend the analyses of the $\mathrm{C}\phantom{\rule{0.16em}{0ex}}{\phantom{\rule{0.16em}{0ex}}}_{\stackrel{P\vec}{}}\phantom{\rule{0.16em}{0ex}}\mathrm{D}$ module to realistic targets and show that the entanglement advantage is maintained albeit reduced. In particular, the conversion module allows exact and efficient performance evaluation despite the non-Gaussian nature of the quantum channel involved.
Quantum illumination is an entanglement-based target detection protocol that provides quantum advantages despite the presence of entanglement-breaking noise. However, the advantage of traditional quantum illumination protocols is limited to impractical scenarios with low transmitted power and simple target configurations. In this work, we propose a quantum illumination network to overcome the limitations, via designing a transmitter array and a single receiver antenna. Thanks to multiple transmitters, quantum advantage is achieved even with a high total transmitted power. Moreover, for single-parameter estimation, the advantage of network over a single transmitter case increases with the number of transmitters before saturation. At the same time, complex target configurations with multiple unknown transmissivity or phase parameters can be resolved. Despite the interference of different returning signals at the single antenna and photon-loss due to multiple-access channel, we provide two types of measurement design, one based on parametric-amplification and one based on the correlation-to-displacement conversion (CtoD) to achieve a quantum advantage in estimating all unknown parameters. We also generalize the parameter estimation scenario to a general hypothesis testing scenario, where the six-decibel quantum illumination advantage is achieved at a much greater total probing power.
Quantum illumination is an entanglement-based target detection protocol that provides quantum advantages despite entanglement-breaking noise. However, the advantage of traditional quantum illumination protocols is limited to impractical scenarios with low transmitted power and simple target configurations. Here, we address these challenges by introducing a quantum illumination network that leverages a transmitter array and a single receiver antenna. Thanks to multiple transmitters, quantum advantage is achieved with a high total transmitted power. Furthermore, the network resolves complex target configurations involving multiple unknown transmissivity or phase parameters. Despite the interference of different returning signals at the single antenna and photon loss due to multiple-access channels, we develop two types of measurement designs: one based on parametric amplification and the other on correlation-to-displacement conversion. Finally, we generalize the parameter estimation scenario to a general hypothesis testing scenario, where the six-decibel quantum illumination advantage is achieved at a much greater total probing power. A quantum illumination protocol with a network of transmitters and a single receiver antenna is proposed. This protocol reaches a quantum advantage at high transmitted power and is applied to low-reflectivity target detection, pattern recognition, and multiple-phase sensing.