Optical communication is the standard for high-bandwidth information transfer in today’s digital age. The increasing demand for bandwidth has led to the maturation of coherent transceivers that use phase- and amplitude-modulated optical signals to encode more bits of information per transmitted pulse. Such encoding schemes achieve higher information density, but also require more complicated receivers to discriminate the signaling states. In fact, achieving the ultimate limit of optical communication capacity, especially in the low light regime, requires coherent joint detection of multiple pulses. Despite their superiority, such joint detection receivers are not in widespread use because of the difficulty of constructing them in the optical domain. In this work we describe how optomechanical transduction of phase information from coherent optical pulses to superconducting qubit states followed by the execution of trained short-depth variational quantum circuits can perform joint detection of communication codewords with error probabilities that surpass all classical, individual pulse detection receivers. Importantly, we utilize a model of optomechanical transduction that captures non-idealities such as thermal noise and loss in order to understand the transduction performance necessary to achieve a quantum advantage with such a scheme. We also execute the trained variational circuits on an IBM-Q device with the modeled transduced states as input to demonstrate that a quantum advantage is possible even with current levels of quantum computing hardware noise.

中文翻译：

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用于光通信的量子计算机接收器


光通信是当今数字时代高带宽信息传输的标准。对带宽的需求不断增加，导致相干收发器日趋成熟，这些收发器使用相位和幅度调制光信号在每个传输脉冲中编码更多比特的信息。这种编码方案实现了更高的信息密度，但也需要更复杂的接收器来区分信令状态。事实上，要达到光通信容量的极限，特别是在弱光条件下，需要对多个脉冲进行相干联合检测。尽管它们具有优越性，但由于在光域中构建它们的困难，这种联合检测接收器并未得到广泛使用。在这项工作中，我们描述了相位信息从相干光脉冲到超导量子位状态的光机械转换，然后执行经过训练的短深度变分量子电路，如何能够以超越所有经典的单独脉冲检测接收器的错误概率对通信码字进行联合检测。重要的是，我们利用光机械转换模型来捕获热噪声和损耗等非理想因素，以便了解通过这种方案实现量子优势所需的转换性能。我们还在 IBM-Q 设备上执行经过训练的变分电路，并以建模的转换状态作为输入，以证明即使在当前的量子计算硬件噪声水平下，量子优势也是可能的。