Quantum Measurements for Continuous-Variable States with Photon Counting

光场状态的测量是物理和工程领域许多技术应用的核心，包括光通信、传感和计量以及信息处理。当光态编码信息时，最优或接近最优的测量允许有效可靠地解码这些信息，增强通信和信息处理中不同协议的性能。测量的设计和优化关键取决于光态的固有特性和要实现的测量中的可用资源。该项目将基于光子计数测量和优化相干位移操作，研究由相干态（来自激光的光）和态叠加组成的光学态的最佳和接近最佳量子测量。相干态及其叠加态的优化测量可以为全光量子信息处理和远程量子通信协议提供新的工具。此外，设计光量子态的有效量子测量对于光子量子技术的当前和未来发展至关重要，这是世界范围内许多学术和工业努力的主题。量子测量理论提供了对确定量子系统状态的可实现灵敏度极限的基本理解。该项目将展示相干态及其叠加的优化量子测量，用于量子通信、信息处理和计算。这些优化的测量基于光子计数、相干位移操作和自适应测量，这将允许为不同状态和测量问题设计广泛的优化量子测量。所提出的相干态量子测量寻求实现复杂的射影和非射影测量，其保真度和灵敏度超出了包括高斯测量（差/外差）在内的标准测量范式。该项目将通过开发高保真度超灵敏光学测量的实验技术，以及利用有限资源设计和优化复杂量子测量的理论方法，推进新知识的发展。理论工作将集中在基于光子计数、相干位移和自适应策略的相干态及其叠加的量子测量上。实验工作将集中在桌面实验中对这些策略的演示。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Measurement of the state of an optical field is at the center of many technological applications across physics and engineering including optical communications, sensing and metrology, and information processing. When the optical state encodes information, optimal or near optimal measurements allow for decoding this information efficiently and reliably, enhancing the performance of different protocols in communications and information processing. The design and optimization of measurements critically depend on the intrinsic properties of the optical states and the available resources in the measurement to be realized. This project will investigate optimal and near optimal quantum measurements for optical states comprised of coherent states (light from lasers) and state superpositions, based on photon counting measurements and optimized coherent displacement operations. Optimized measurements for coherent states and their superpositions can provide a new tool for protocols in all-optical quantum information processing and long-distance quantum communications. Furthermore, the design of efficient quantum measurements for optical quantum states is essential for current and future developments in photonic quantum technologies, which are the subject of many academic and industrial efforts worldwide.Quantum measurement theory provides a fundamental understanding of the limits on the achievable sensitivity for determining the states of quantum systems. This project will demonstrate optimized quantum measurements for coherent states and their superpositions for applications in quantum communications, information processing, and computation. These optimized measurements are based on photon counting, coherent displacement operations, and adaptive measurements, which will allow for the design of a wide class of optimized quantum measurements for diverse states and measurement problems. The proposed quantum measurements of coherent states seek to realize complex projective and non-projective measurements with fidelities and sensitivities for state projection and discrimination beyond the reach of standard measurement paradigms including Gaussian measurements (homodyne/heterodyne). The project will advance new knowledge through the development of experimental techniques for ultrasensitive optical measurements with high fidelity, and through theoretical methods for the design and optimization of complex quantum measurements with finite resources. Theoretical efforts will focus on quantum measurements of coherent states and their superpositions based on photon counting, coherent displacements, and adaptive strategies. Experimental efforts will focus on the demonstrations of these strategies in tabletop experiments.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.