微波波段的双向隐蔽量子通信
Two-way covert quantum communication in the microwave regime
摘要：
量子通信通过采用基于量子力学定律的加密技术来解决跨宏观距离交换信息的问题。在这里，我们提出了一个新的范例，安全的量子通信相结合的背散射概念与隐蔽通信的微波制度。我们的协议允许Alice（仅使用离散相位调制）和Bob（可以使用低温微波技术）之间的通信。使用量子信道鉴别和量子精密测量的概念，我们找到了接收机性能的最终界限，证明量子相关性可以提高SNR高达$6$ dB。这些界限排除了任何量子照明的优势时，源被强烈放大，并表明，只有在低光子数制度的相关增益是可能的。我们展示了该协议如何用于隐蔽通信，其中载波信号与环境中的热噪声无法区分。我们补充我们的信息理论的结果与一个可行的实验建议在电路QED平台。这项工作朝着在以前未知的$1$ - $10$ GHz频率范围内实现安全量子通信概念迈出了决定性的一步，在这种情况下，一方的可支配功率受到严重限制。
英文摘要：
Quantum communication addresses the problem of exchanging information across macroscopic distances by employing encryption techniques based on quantum mechanical laws. Here, we advance a new paradigm for secure quantum communication by combining backscattering concepts with covert communication in the microwave regime. Our protocol allows communication between Alice, who uses only discrete phase modulations, and Bob, who has access to cryogenic microwave technology. Using notions of quantum channel discrimination and quantum metrology, we find the ultimate bounds for the receiver performance, proving that quantum correlations can enhance the SNR by up to $6$ dB. These bounds rule out any quantum illumination advantage when the source is strongly amplified, and show that a relevant gain is possible only in the low photon-number regime. We show how the protocol can be used for covert communication, where the carrier signal is indistinguishable from the thermal noise in the environment. We complement our information-theoretic results with a feasible experimental proposal in a circuit-QED platform. This work makes a decisive step toward implementing secure quantum communication concepts in the previously uncharted $1$-$10$ GHz frequency range, in the scenario when the disposable power of one party is severely constrained.
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