Optimal entanglement-assisted electromagnetic sensing and communication in the presence of noise
Haowei Shi, Bingzhi Zhang, Jeffrey H. Shapiro, Zheshen Zhang, Quntao Zhuang · Physical Review Applied · 2024
High time-bandwidth product signal and idler pulses comprised of independent identically distributed two-mode squeezed vacuum (TMSV) states are readily produced by spontaneous parametric down-conversion. These pulses are virtually unique among entangled states in that they offer quantum performance advantages---over their best classical-state competitors---in scenarios whose loss and noise break their initial entanglement. Broadband TMSV states' quantum advantage derives from its signal and idler having a strongly nonclassical phase-sensitive cross correlation, which leads to information-bearing signatures in lossy, noisy scenarios stronger than what can be obtained from classical-state systems of the same transmitted energy. Previous broadband TMSV receiver architectures focused on converting phase-sensitive cross correlation into phase-insensitive cross correlation, which can be measured in second-order interference. In general, however, these receivers fail to deliver broadband TMSV states' full quantum advantage, even if they are implemented with ideal equipment. This paper introduces the correlation-to-displacement receiver---an alternative architecture comprised of a correlation-to-displacement converter, a programmable mode selector, and a coherent-state information extractor---that can be configured to achieve quantum optimal performance in known sensing and communication protocols for which broadband TMSV provides quantum advantage that is robust against entanglement-breaking loss and noise.