Collaborative Research: CIF: FET: Small: Realizing Joint Detection Receivers for Quantum-enhanced Optical Communications using Photonic NISQ-era Quantum Processors

光激光通信将构成包括深空通信在内的未来天基数据通信系统的关键组成部分。与传统的射频通信相比，它可以支持更高的数据速率，而对尺寸、重量和传输功率的要求更低。最终的数据速率，或者换句话说，远程光学激光通信链路的通信能力，受量子物理定律的支配。为了达到这些从根本上优于传统光接收器所支持的速率的极限数据速率，需要基于量子物理的新型接收器。然而，设计这种量子接收器的最佳版本的结构化方法仍然未知。最近提出的一种称为量子消息信任传播的量子解码算法有望成为一种近乎最佳的设计方法。该项目将研究使用该算法为一大类通信代码和光学调制格式设计量子接收器。众所周知，接收器设计原则上可以在光子量子硬件上实现。拟议的项目将探索在世外桃源量子技术公司的商用光子量子处理器上实现接收器电路所需的量子逻辑的替代实现，并确定资源最优的实现。该项目的成功将使光通信速率比NASA未来的深空光学激光通信系统高出5倍。此外，在世外桃源的光子处理器上成功实现接收器，将相当于在实际应用中展示出使用近期噪声量子处理器进行的量子处理相对于经典处理的量子优势，这是当今量子信息处理中的重要探索。这项拟议的研究将为量子增强经典光通信的研究生课程提供新的内容。该项目将加强亚利桑那大学和德克萨斯大学奥斯汀分校的持续努力，为新兴量子信息技术领域中代表性不足的群体的学生提供教育和研究机会。拟议的项目旨在设计和实现用于量子增强光激光通信的量子联合检测接收器(JDR)，涉及对接收到的光脉冲块进行预检测、集体和量子域处理。该项目的设计部分将利用一种量子译码算法，即带有量子消息的信任传播(BPQM)，该算法最近被证明对于基于示例性5比特树码的二进制相移键控调制激光通信系统达到了最小块译码错误概率的量子极限。对于低密度奇偶校验码和不同的光调制格式，将研究BPQM算法。关于实现，Lasercom基于BPQM的JDR设计很容易转换为量子电路，该电路可在能够执行CAT-BASE量子逻辑的短期、非纠错、光子、噪声中等规模量子(NISQ)处理器上执行。实现基于CAT的逻辑的基本门有多种方法可供选择，其中资源优化的方法是未知的。为了确定最佳方法，作为项目的一部分，将使用世外桃源量子技术公司的光子量子硬件，为不同方法的基本构件建立理论和实验噪声模型。数值模拟了基于BPQM的JDR对于简单的3比特和5比特树码的预期性能。BPQM-JDR的光量子电路的完整蓝图将在世外桃源的光子量子处理器上开发和实现，该蓝图将根据所确定的5位线性树码的CAT基逻辑的最佳实现来实现。调制量子光的普遍量子逻辑操作是其他一些量子增强的经典通信和传感应用的基础，例如，纠缠辅助的经典射频通信和传感器，如分布式时钟和长基线望远镜。NISQ时代的光子量子硬件可能已经可以为其中一些应用提供动力，但需要协调一致的量子工程努力才能利用它们现有的能力。拟议的项目将加速这一进程，产生强大的社会和经济影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Optical laser communication will constitute a key component of future space-based data communication systems including deep-space communications. It can support significantly higher data rates compared to traditional radio-frequency communication with lower size, weight and transmission power requirements. The ultimate data rates, or in other words, the communication capacity of long-range optical lasercom links, are governed by the laws of quantum physics. Novel receivers based on quantum physics are required in order to attain these ultimate data rates, which are fundamentally superior to the rates supported by conventional optical receivers. However, a structured methodology for designing optimal versions of such quantum receivers had remained unknown. A recently proposed quantum decoding algorithm known as belief propagation with quantum messages promises to be a near-optimal design methodology. The project will investigate the use of this algorithm to design quantum receivers for a large class of communication codes and optical modulation formats. The receiver designs are known to be in principle realizable on photonic quantum hardware. The proposed project will explore alternative implementations of the quantum logic required to realize the receiver circuitry on the commercially-available photonic quantum processor of Xanadu Quantum Technologies and determine the resource-optimal implementation. The success of this project would enable up to 5x higher optical communication rates over NASA’s future deep-space optical lasercom systems. Moreover, a successful realization of the receiver on Xanadu’s photonic processor would amount to a demonstration of quantum advantage over classical processing using a near-term noisy quantum processor in a practical application, which is an important quest in quantum information processing today. The proposed research will provide new content for a graduate course on quantum-enhanced classical optical communications. The project will augment the continued efforts of University of Arizona and University of Texas at Austin to provide educational and research opportunities to students from under-represented groups in the emerging field of quantum information technologies.The proposed project is aimed at designing and implementing quantum joint detection receivers (JDRs) for quantum-enhanced optical laser communication that involve pre-detection, collective, quantum-domain processing of blocks of received optical pulses. The design part of the project will utilize a quantum decoding algorithm, belief propagation with quantum messages (BPQM), which for a binary phase shift keying-modulated lasercom system based on an exemplary 5-bit tree code was recently shown to attain the quantum limit of minimum block decoding error probability. The BPQM algorithm will be investigated for low-density parity check codes and for different optical modulation formats. Pertaining to implementation, the BPQM-based JDR design for lasercom readily translates into a quantum circuit that is executable on a near-term, non-error-corrected, photonic, noisy intermediate-scale quantum (NISQ) processor capable of performing cat-basis quantum logic. Several alternative approaches are available to realize the elementary gates of cat-basis logic, among which the resource-optimal approach is unknown. In order to identify the optimal approach, as part of the project, theoretical and experimental noise models will be built for the basic building blocks of the different approaches using the photonic quantum hardware of Xanadu Quantum Technologies. The expected performance of the BPQM-based JDR for simple 3- and 5-bit tree code examples will be numerically simulated. A complete blueprint of the optical quantum circuit of the BPQM-JDR in terms of the identified optimal implementation of cat-basis logic for the 5-bit linear tree code will be developed and realized over Xanadu’s photonic quantum processor. Universal quantum-logic manipulation of modulated quantum light underlies a number of other quantum-enhanced classical communications and sensing applications, e.g., entanglement-assisted classical radio-frequency communications and sensors such as distributed clocks and long-baseline telescopes. NISQ-era photonic quantum hardware can potentially already power some of these applications but require a concerted quantum engineering effort to leverage their existing capabilities. The proposed project will accelerate this process for strong societal and economic impact.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.