Signal processing stands as a pillar of classical computation and modern information technology, applicable to both analog and digital signals. Recently, advancements in quantum information science have suggested that quantum signal processing (QSP) can enable more powerful signal processing capabilities. However, the developments in QSP have primarily leveraged \emph{digital} quantum resources, such as discrete-variable (DV) systems like qubits, rather than \emph{analog} quantum resources, such as continuous-variable (CV) systems like quantum oscillators. Consequently, there remains a gap in understanding how signal processing can be performed on hybrid CV-DV quantum computers. Here we address this gap by developing a new paradigm of mixed analog-digital QSP. We demonstrate the utility of this paradigm by showcasing how it naturally enables analog-digital conversion of quantum signals -- specifically, the transfer of states between DV and CV quantum systems. We then show that such quantum analog-digital conversion enables new implementations of quantum algorithms on CV-DV hardware. This is exemplified by realizing the quantum Fourier transform of a state encoded on qubits via the free-evolution of a quantum oscillator, albeit with a runtime exponential in the number of qubits due to information theoretic arguments. Collectively, this work marks a significant step forward in hybrid CV-DV quantum computation, providing a foundation for scalable analog-digital signal processing on quantum processors.
All-Digital LoS MIMO with Low-Precision Analog-to-Digital Conversion
视线（LoS）多输入多输出（MIMO）系统随着载波频率的增加而表现出有吸引力的缩放特性：对于固定的形状因子和范围，除了可用带宽的典型线性增加之外，二维阵列的空间自由度以二次方式增加。在本文中，我们研究了现代全数字基带信号处理架构是否可以设计这样的制度，给定的大带宽的模数转换的困难。我们提出了低精度量化器设计和相应的空间解复用算法，考虑2x2 LoS MIMO与QPSK的分析见解，以及4x4 MIMO与QPSK和16QAM的性能评估。与现有技术不同，信道状态信息仅在接收机处使用（即，不采用发射预编码）。我们研究具有规则结构的量化器，其高信噪比互信息接近未量化系统的互信息。我们证明，幅相量化是必要的，以达到这一基准，相位量化不足。我们表明，基于最大化每天线输出熵的量化器比标准的最小均方量化误差（MMSQE）量化性能更好。对于空间解复用严重量化的意见，我们引入了新的概念，虚拟量化，结合线性检测，提供了可靠的解调在显着降低复杂性相比，最大似然检测。
A Timing-Robust Frequency-Interleaved ADC with Embedded Analog Fourier Transform
Institute of Integrated Circuits and Systems, University of Electronic Science and Technology of China（电子科技大学集成电路与系统研究所）；Hamburg University of Technology（汉堡工业大学）
