Efficient and Versatile Fiber-based Quantum Photonic Sources

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Quantum photonic sources are to quantum technology what lasers are to optical technology. In the 50 years after the invention of laser, lasers have emerged from a laboratory curiosity to a necessity in everyday life. Its applications cover everything from DVD players to industrial cutting and welding, from laser surgery to long-distance communication. Indeed, the Internet would not have been possible without lasers. Analogously, quantum photon sources will likely play an equally important role as lasers do in not too distant future. They produce photons exhibiting quantum correlations that cannot be mimicked by classical particles. The quantum correlations can be harnessed to perform functions impossible to achieve classically, such as unconditional security in communication, efficient algorithm in quantum computing, and ultra-high resolution in quantum imaging. A basic quantum photonic source produces entangled photon pairs, which, broadly speaking, are pairs of photons (or light particles) prepared in a special quantum state that makes them exhibit correlated properties. For example, for polarization-entangled photon pairs, the measurement of one photon’s polarization state reveals that of its partner, even when they are physically far away from each other—a phenomenon once described by Einstein as “spooky action at a distance”. It is this “spookiness”, or non-intuitiveness, that inspired the unconventional usage of the quantum resource. Entanglement-based quantum key distribution (QKD), for example, utilizes the correlation of the photons sent to two remote parties and allows them to share a common set of random cryptographic keys. It guarantees the security of the keys since any eavesdropping attempt would result in a detectable deterioration of correlation. Entangled photons are also used to construct many other types of quantum photonic sources, such as heralded single photon sources, multi-photon entanglement sources, etc. They are essential tools for quantum computing, quantum communication, quantum metrology, and quantum lithography. Here we propose to develop an efficient and versatile quantum photonic source using optical fibre. Entangled photon pairs can be generated from higher energy photons in a nonlinear optical material. Optical fibre is typically inefficient for this purpose due to its weak nonlinearity. We propose to use poled fibre, one that has been subject to a high electric field, for efficient entangled photon pair generation. Compact, robust, fibre-based sources are highly desirable for both QKD and metrology applications that use fibre for transmission or photon delivery, because they remove the need for beam alignment, eliminate coupling losses to and from fibre, and facilitate turn-key operation perfect for field deployment. Quantum technology will play an important role in the 21st century. Quantum photonic sources are essential for many quantum applications. This proposal aims to take an important step forward in the development of quantum technology for practical applications.