Collaborative Research: FET: Small: Towards full photon utilization by adaptive modulation and coding on quantum links

长期以来，安全通信一直是众多系统不可或缺的一部分，从金融和国防等更传统的系统，到物联网(战场)和健康数据管理等新兴系统。基于公钥的传统数据加密方法受到量子计算算法的发展的威胁，量子计算算法有望有效地解决使公钥加密安全的本来难以解决的问题。然而，正是量子信息处理的进步也有望通过允许高效和安全的私钥分发来实现安全通信。私钥加密的主要优点是，只要密钥字符串是真正保密的，它就是可证明的安全的，也就是说，对计算的进步不敏感。量子密钥分发(QKD)协议描述了通常被称为Alice和Bob的双方如何通过在都可以被窃听者Eve访问的量子和公共经典信道上通信来建立秘密密钥。为了广泛采用QKD，必须在远距离提供高密钥速率。在实践中出现的瓶颈是无法最大限度地利用承载信息的量子态。这个项目试图解决这个效率低下的问题。这一结果将为实际量子网络中多个接收者通过多通道纠缠分布同时与源进行通信铺平道路。本项目的重点是通过结合自适应光子产生感知调制和编码的创新以及最先进的实验验证，最大化光子在基于频率-时间纠缠的量子密钥分配中的效用。QKD提供了一种物理上安全的方法，用于在量子和公共通信通道上建立加密密钥，这两个通道都可以被窃听者观察到。由于对量子通信的需求日益增长，对改进量子密钥分发协议的研究也急剧加强。最近的一项突破是对连续可变频率-时间超纠缠光子的实验观察。这种高维大希尔伯特空间的方法通过潜在地在每个纠缠的光子对中携带多个比特来保证高信息效率。然而，为了确保量子密钥分发的无条件安全，必须在光子匮乏的条件下传输双光子(无论是每个光子携带单个量子比特还是多个量子比特)，因此迫切需要最大限度地利用所有生成的双光子。该项目将提供由光子感知调制和编码方案组成的集成解决方案，并将是第一个在时间轴编码的多维双光子上进行演示的解决方案。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。

Secure communication has long been an indispensable part of numerous systems, ranging from the more traditional such as finance and defense to the emerging ones such as the internet of (battlefield) things and health data management. Traditional data encryption methods based on using public keys are threatened by the advances in quantum computing algorithms promising to efficiently solve otherwise intractable problems which make public key encryption secure. However, it is precisely quantum information processing advances that are also expected to enable secure communications by allowing efficient and secure private key distribution. The main advantage of private key encryption is that as long as the key strings are truly secret, it is provably secure, that is, insensitive to advances in computing. A Quantum Key Distribution (QKD) protocol describes how two parties, commonly referred to as Alice and Bob, can establish a secret key by communicating over a quantum and a public classical channel that both can be accessed by an eavesdropper Eve. For the widespread adoption of QKD, it is mandatory to provide high key rates over long distances. What has appeared as a bottleneck in practice is the inability to maximize the utility of information-bearing quantum states. This project seeks to solve this inefficiency problem. The results will pave the way for practical quantum networks in which multiple receivers communicate with a source simultaneously though multi-channel entanglement distribution.This project focuses on maximizing the utility of photons in frequency-time entanglement based QKD, through a combination of innovations in adaptive photon generation-aware modulation and coding, and a state of the art experimental validation. QKD offers a physically secure way for establishing an encryption key over a quantum and a public communication channel, both of which are observed by an eavesdropper. Because of the growing demand for quantum communications, research on improving QKD protocols has steeply intensified. One recent breakthrough is the experimental observation of continuous-variable frequency-time hyperentangled photons. This high-dimensional large Hilbert-space approach promises high information efficiency by potentially carrying multiple bits per an entangled photon pair. However, to ensure unconditional security in QKD, the biphotons (whether carrying single qubit or multiple qubits per photon), must be transmitted under photon-starved conditions, creating an immediate need to maximize utility of all generated biphotons. The project will offer an integrated solution consisting of photon-aware modulation and coding schemes, and will be the first such to be demonstrated on time-bin encoded multi-dimensional biphotons.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.