Photonic quantum technologies

We have just witnessed the birth of the first quantum technology based on encoding information in light for quantum key distribution. The quantum nature of light seems destined to continue to have a central role in future technologies. Here we provide a broad review of photonics for quantum technologies touching on topics including secure communication with photons, quantum information processing, quantum lithography and integrated quantum photonics. The first quantum technology that harnesses quantum mechanical effects for its core operation has arrived in the form of commercially available quantum key distribution systems. This technology achieves enhanced security by encoding information in photons such that an eavesdropper in the system can be detected. Anticipated future quantum technologies include large-scale secure networks, enhanced measurement and lithography, and quantum information processors, which promise exponentially greater computational power for particular tasks. Photonics is destined to have a central role in such technologies owing to the high-speed transmission and outstanding low-noise properties of photons. These technologies may use single photons, quantum states of bright laser beams or both, and will undoubtedly apply and drive state-of-the-art developments in photonics.