Title: Quantum Approximate Optimization Algorithm for MIMO with Quantized b-bit Beamforming Show Chinese title

Title: 用于具有量化b位波束成形的MIMO的量子近似优化算法

Abstract: Multiple-input multiple-output (MIMO) is critical for 6G communication, offering improved spectral efficiency and reliability. However, conventional fully digital designs face significant challenges due to high hardware complexity and power consumption. Low-bit MIMO architectures, such as those employing b-bit quantized phase shifters, provide a cost-effective alternative but introduce NP-hard combinatorial problems in the pre- and post-coding design. This paper explores the use of the Quantum Approximate Optimization Algorithm (QAOA) and alternating optimization to address the problem of b-bit quantized phase shifters both at the transmitter and the receiver. We demonstrate that the structure of this quantized beamforming problem aligns naturally with hybrid-classical methods like QAOA, as the phase shifts used in beamforming can be directly mapped to rotation gates in a quantum circuit. Notably, this paper is the first to show that theoretical connection. Then, the Hamiltonian derivation analysis for the b-bit case is presented, which could have applications in different fields, such as integrated sensing and communication, and emerging quantum algorithms such as quantum machine learning. In addition, a warm-start QAOA approach is studied which improves computational efficiency. Numerical results highlight the effectiveness of the proposed methods in achieving an improved quantized beamforming gain over their classical optimization benchmarks from the literature. Show Chinese abstract

Abstract: 多输入多输出（MIMO）对于6G通信至关重要，它提供了改进的频谱效率和可靠性。 然而，传统的全数字设计由于高硬件复杂度和功耗而面临重大挑战。 低比特MIMO架构，例如使用b比特量化相移器的架构，提供了一种成本效益高的替代方案，但在预编码和后编码设计中引入了NP难的组合问题。 本文探讨了量子近似优化算法（QAOA）和交替优化在发射端和接收端解决b比特量化相移器问题的应用。 我们证明了这种量化波束成形问题的结构自然地与混合经典方法如QAOA相契合，因为在波束成形中使用的相移可以直接映射到量子电路中的旋转门。 值得注意的是，本文是首次展示这一理论联系。 随后，给出了b比特情况的哈密顿量推导分析，这可能在不同领域如集成感知与通信以及新兴的量子算法如量子机器学习中具有应用。 此外，研究了一种热启动QAOA方法，以提高计算效率。 数值结果突显了所提出方法在实现比文献中经典优化基准更好的量化波束成形增益方面的有效性。