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Photonic integrated circuits hold great promise in enabling the practical wide-scale deployment of quantum communications; however, despite impressive experiments of component functionality, a fully operational quantum communication system using photonic chips is yet to be demonstrated. Here we demonstrate an entirely standalone secure communication system based on photonic integrated circuits—assembled into compact modules—for quantum random number generation and quantum key distribution at gigahertz clock rates. The bit values, basis selection and decoy pulse intensities used for quantum key distribution are chosen at random, and are based on the output of a chip-based quantum random number generator operating at 4 Gb s–1. Error correction and privacy amplification are performed in real time to produce information-theoretic secure keys for a 100 Gb s–1 line speed data encryption system. We demonstrate long-term continuous operation of the quantum secured communication system using feedback controls to stabilize the qubit phase and propagation delay over metropolitan fibre lengths. These results mark an important milestone for the realistic deployment of quantum communications based on quantum photonic chips. Quantum photonic integrated circuits for a standalone quantum secure communication system are developed and packaged into pluggable interconnects. The system is interfaced with 100 Gb s–1 data encryptors and its performance is evaluated over 10 km to 50 km fibre links.

Quantum key distribution (QKD) is the best candidate for securing communications against attackers, who may in the future exploit quantum-enhanced computational powers to break classical encryption. As such, new challenges are arising from our need for large-scale deployment of QKD systems. In a realistic scenario, transmitting and receiving devices from different vendors should be able to communicate with each other without the need for matching hardware. Therefore, practical deployment of QKD would require hardware capable of adapting to different protocols and clock rates. Here, we address this challenge by presenting a multi-rate, multi-protocol QKD transmitter linked to a correspondingly adaptable QKD receiver. The flexibility of the transmitter, achieved by optical injection locking, allows us to connect it with two receivers with inherently different clock rates. Furthermore, we demonstrate the multi-protocol operation of our transmitter, communicating with receiving parties employing different decoding circuits., Comment: 7 pages, 4 figures

Integrated photonics can enable a wide deployment of quantum cryptography but this integration is technologically challenging. We addressed the challenges and built a complete, real-time and deployable quantum key distribution system based on integrated photonics.

The practical combination of quantum cryptography and classical communications will require convergence of their technologies. In this pivotal time where both fields are transitioning towards photonic integrated architectures, it is essential to develop devices that fully leverage their hardware compatibilities, while still addressing the key issues of cost reduction, miniaturization and infrastructure energetic footprint, essential for future high- bandwidth, low-latency networks. Here, we address these issues by developing an on-chip transmitter consisting of just 3 building blocks but capable of transmitting both quantum encrypted photons and classical multi-level modulation signals. By combining optical injection locking and direct phase modulation we are able to encode pulse trains with multiple levels of differential phase, without the need of high-speed electro-optic modulators and their associated power footprint. We generate return-to-zero differential phase shift keying signals with up to 16 distinct levels. Moreover, we demonstrate multi-protocol quantum key distribution delivering state-of-the-art secure key rates. Our on-chip transmitter will facilitate the flexible combination of quantum and classical communications within a single, power-efficient device that can readily be integrated in existing high connectivity networks.

We demonstrate on-chip quantum random number generation at high data rates using the random phases of gain-switched laser pulses. Interference of the gain-switched pulses produced by two independent semiconductor lasers is performed on a photonic integrated circuit (PIC) and the resulting pulse train is received and processed in real-time using homebuilt capture electronics consisting a field programmable gate array (FPGA) and a 10-bit digitizer. Random numbers with low correlation coefficient are shown for pulse clock rates of 1 GHz and data rates of 8 Gbps. The random numbers are also shown to successfully pass all tests within the National Institute for Standards and Technology (NIST) test suite. The system provides genuine random numbers in a compact platform that can be readily integrated into existing quantum cryptographic technology., Comment: 7 pages, 3 figures

Solutions for a practical, wide-scale deployment of quantum secure communication devices have long been awaited for. Recent reports of quantum key distribution (QKD) chips, yet promising, were restricted to proof-of-concepts of individual components. We now demonstrate a complete QKD system, entirely based on photonic chips and distributing quantum secure encryption keys at high bit rate. This establishes photonic integration as a viable solution for a low-cost, scalable deployment of QKD.

There is growing incentive to integrate quantum communication technologies into our high-bandwidth communication networks. However, for a realistic and practical large-scale deployment, drastic reductions of the size, cost and power consumption of current quantum cryptographic systems are necessary. We show how this goal can be achieved using photonic integration. We demonstrate quantum communication chips capable of record performances including quantum key distribution at 250kb/s over a 20dB-loss channel and quantum random number generation at 8Gb/s. The scalability and affordability of these new devices will allow the deployment of quantum cryptography in high connectivity networks.