Quantum communication based on entanglement and hyper-entanglement

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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.