Quantum communication based on entanglement and hyper-entanglement

纠缠是量子物理学的核心。量子纠缠是许多量子通信协议的重要资源，如量子隐形传态和量子密集编码，量子密码学，以及量子增强的量子通信方案和量子计算。量子方案允许在性能上显著优于经典方案，因此在可预见的未来，利用纠缠光子的商业实现是可能的。量子光子技术的一个关键使能组件是纠缠光子源。 我们开发了一种独特的技术，可以直接在光纤中产生纠缠和超纠缠光子对。我们的技术得到了全球量子光子学界的广泛认可，并已被我们的加拿大工业合作伙伴OZ Optics商业化。基于我们技术的商业纠缠光子源已经出售给许多研究机构，包括NIST，贝尔实验室，美国ARL，仅举几例。在我们成功演示基于光纤的纠缠光子源的基础上，我们继续开发更复杂的纠缠光子源，如超纠缠源，并探索利用光子纠缠和超纠缠的量子通信应用。为了实现量子增强协议（如安全量子通信和分布式量子计算）的全球规模实现，量子通信中要解决的一个关键挑战是长距离纠缠的分布。然而，噪声和与环境的相互作用导致退相干和纠缠的退化。为了抵消这种不利的噪声影响，纠缠纯化被引入作为一种强有力的工具，从污染的低质量纠缠态中提取高质量的纠缠态。 我们提出了一个高效率的纠缠纯化协议，使用我们独特的基于光纤的源产生的超纠缠光子对。我们的方法有一些实际的优点：我们可以使用标准的电信光纤传输超纠缠光子鲁棒;我们可以实现高质量的偏振纠缠后，纯化。我们的方法将使广泛的量子通信和计算协议的基础上纠缠分布在实际的，嘈杂的信道。 为了实现我们的目标，我们要求更新一个有20年历史的激光系统，该系统被用作光纤源的泵浦，以产生纠缠光子，并作为系统中的一个组成部分，以实现纠缠纯化。该设备是我们继续纠缠光子及其应用研究不可缺少的。

Entanglement lies at the heart of quantum physics. Quantum entanglement is an essential resource for numerous quantum communication protocols such as quantum teleportation and quantum dense coding, quantum cryptography, as well as quantum-enhanced metrological schemes and quantum computation. Quantum schemes allow for significant gains in performance over their classical counterparts, and commercial implementations utilizing entangled photons are thus likely in the foreseeable future. One key enabling component for quantum photonic technology is the entangled photon sources.  We have developed a unique technology to generate entangled and hyper-entangled photon pairs directly in optical fiber. Our technology is broadly recognized by the quantum photonics community worldwide, and has been commercialized by our Canadian industrial partner, OZ Optics. The commercial entangled photon sources based on our technology have been sold to many research institutions, including NIST, Bell Labs, US ARL, to name a few. Built on our successful demonstration of fibre-based entangled photon sources, we continue the development of more sophisticated entangled photon sources, such as hyper-entangled sources, and we explore quantum communication applications utilizing photonic entanglement and hyper-entanglement. A key challenge to be addressed in quantum communication, in order to achieve a global-scale implementation of quantum-enhanced protocols, such as secure quantum communication and distributed quantum computing, is the distribution of entanglement over long distances. However, noise and interaction with the environment lead to decoherence and the degradation of entanglement. To counteract such detrimental noise effects, entanglement purification was introduced as a powerful tool to distill high-quality entangled states from the polluted low-quality entangled states. We propose a high-efficiency entanglement purification protocol using hyper-entangled photon pairs produced by our unique fibre-based sources. Our approach has a few practical advantages: We can use standard telecom fiber to transmit hyper-entangled photons robustly; and we can achieve high-quality polarization entanglement after purification. Our approach will enable a wide range of quantum communication and computing protocols based on entanglement distribution over practical, noisy channels. To achieve our goal, we request equipment to renew a 20-year-old laser system, which is used as a pump to the fibre-based source to produce entangled photons, and as an integral component in a system to achieve entanglement purification. The equipment is indispensable for us to continue our research in entangled photons and in their applications.