A research team at the University of Bristol has demonstrated chip-based devices that contain all the optical components necessary for quantum key distribution (QKD). The team showed that secure quantum key exchange could be accomplished between two chip-based devices measuring just 6 × 2 mm over a fiber network with links up to 200 km. The researchers used mass-manufacturable, monolithically integrated transmitters to demonstrate their accessible, quantum-ready communication platform. The new QKD devices are based on the same semiconductor technology found in smartphones and computers. Instead of wires to guide electricity, they contain circuits that control the photonic signals necessary for QKD. Nanoscale components in the chips make it possible to reduce the size and power consumption of QKD while maintaining high-speed performance. New chip-based devices contain all the optical components necessary for quantum key distribution. The cost-effective platform was designed to facilitate citywide networks. Courtesy of Henry Semenenko, University of Bristol. The researchers designed the new platform to facilitate citywide networks and decrease the number of connections required between users. “Our platform allows single users to connect to a centralized node that enables secure communication with every other user,” researcher Henry Semenenko said. “As quantum networks develop, the centralized node will offer crucial infrastructure that will eventually support more complex communication protocols.” The researchers demonstrated their new chip-based devices with a proof-of-principle experiment in which they emulated a 200-km fiber network at the University of Bristol Quantum Engineering Technology Labs. Using two independent chip devices, they showed that error rates and speed were comparable to state-of-the-art commercial components. “We showed that these chip-based devices can be used to produce quantum effects even when photons were generated by different devices,” Semenenko said. “This is vital for quantum networks where each user will control their own devices that are distributed around a city.” The researchers plan to make the system more practical by developing application-specific hardware. They will then use the fiber optic network in place around the city of Bristol to create a model metropolitan network with many users. “With its densely packed optical components, our chip-based platform offers a level of precise control and complexity not achievable with alternatives,” Semenenko said. “It will allow users to access a secure network with a cost-effective device the same size as the routers we use today to access the internet.” The research was published in Optica, a publication of OSA, The Optical Society (www.doi.org/10.1364/OPTICA.379679).