Quantum key distribution (QKD) relies on the fundamental principles of quantum mechanics and can theoretically achieve unconditionally secure communication that is provable by information theory. Quantum random number generators, on the other hand, utilize the inherent randomness of quantum phenomena and are capable of generating a truly random entropy source that is unpredictable, unbiased and unrepeatable. These two technologies are crucial for building highly trustworthy and secure communication systems resistant to quantum attacks. However, their large-scale deployment still faces challenges such as system performance optimization, cost control and scale production. Relying on wafer-level fabrication platforms and micro-nanometer processing, integrated photonics technology integrates the core devices of traditional QKD systems (e.g., light source, modulator, and detector) in a single chip at high density. It significantly improves the miniaturization, operational stability and cost-effectiveness of the system, and enhances the intrinsic security, and becomes a key enabling platform to drive QKD and QRNG from laboratory to engineering applications. In this paper, we systematically review the recent breakthroughs of photonic integrated QKD based on different material platforms (SOI/InP/TFLN/Si3N4) in terms of core metrics, such as transmission distance and key rate, as well as the significant breakthroughs of integrated QRNG in terms of random number generation rate and system integration. Finally, the future development direction of this field is discussed and outlooked from the four dimensions of practical security of QKD systems, on-chip implementation of cutting-edge QKD protocols, practical fully-integrated QKD systems, and synergistic optimization of high performance and high integration of integrated QRNG.
Quantum key distribution (QKD) relies on the fundamental principles of quantum mechanics and can theoretically achieve unconditionally secure communication that is provable by information theory. Quantum random number generators, on the other hand, utilize the inherent randomness of quantum phenomena and are capable of generating a truly random entropy source that is unpredictable, unbiased and unrepeatable. These two technologies are crucial for building highly trustworthy and secure communication systems resistant to quantum attacks. However, their large-scale deployment still faces challenges such as system performance optimization, cost control and scale production. Relying on wafer-level fabrication platforms and micro-nanometer processing, integrated photonics technology integrates the core devices of traditional QKD systems (e.g., light source, modulator, and detector) in a single chip at high density. It significantly improves the miniaturization, operational stability and cost-effectiveness of the system, and enhances the intrinsic security, and becomes a key enabling platform to drive QKD and QRNG from laboratory to engineering applications. In this paper, we systematically review the recent breakthroughs of photonic integrated QKD based on different material platforms (SOI/InP/TFLN/Si3N4) in terms of core metrics, such as transmission distance and key rate, as well as the significant breakthroughs of integrated QRNG in terms of random number generation rate and system integration. Finally, the future development direction of this field is discussed and outlooked from the four dimensions of practical security of QKD systems, on-chip implementation of cutting-edge QKD protocols, practical fully-integrated QKD systems, and synergistic optimization of high performance and high integration of integrated QRNG.
Quantum key distribution (QKD) and quantum random number generation (QRNG) will play a key role in the future of data communication security. QKD can be used by trusted parties to share a secret key, leading to long-term secure communications. QRNG allows the production of fully unpredictable and certifiable random numbers, which can be used in numerous applications, including cryptography and large stochastic simulations. Both QKD and QRNG can be implemented using commercially available photonic components, which are mostly bulky and assembled into a discrete module. Although this approach can benefit from the superior performance and maturity of each individual component, it does not guarantee the large-scale deployment and commercial viability of the technology. A preferable alternative relies on integrating some or all functionalities in a single photonic integrated circuit (PIC) fabricated at the wafer scale, in this way reducing size, weight, complexity, cost, and power consumption. Integrated photonics can thus dramatically improve the performance and reliability of QKD systems and QRNG devices. Here, we review recent literature on designs, related materials, and fabrication processes, which is representative of state-of-the-art PIC-based QKD and QRNG. We conclude the paper by pointing out the challenges that need to be addressed in the future for reaching a wide-scale deployment of these integrated technologies.
Quantum technologies are rapidly transforming the landscape of secure communication and computation by exploiting the fundamental principles of quantum mechanics. Among these, Quantum Key Distribution (QKD) offers an unprecedented level of security in communications, provided by physical principles rather than computational assumptions. However, the realization of scalable and practical quantum networks remains challenging. Key technological hurdles include the need for high-sensitivity and high-speed single-photon detectors, stable and integrated optical platforms, and robust and fast true random number generators. Overcoming these challenges is essential to bridge the gap between laboratory demonstrations and the real-world deployment of quantum networks. This thesis addresses some of these critical issues through work in single-photon detection technologies, integrated QKD system implementation, and high-speed Quantum Random Number Generators (QRNGs). Single-Photon Avalanche Diodes are fundamental detectors for quantum technologies, enabling high-sensitivity measurements at the single-photon level. This thesis investigates the operating principles, limitations, and advancements of Single-Photon Avalanche Diodes, with a focus on high-speed dual-anode designs. Their photon detection efficiency, dark count rate, afterpulsing probability, and timing jitter are analyzed, while optimized control electronics and capacitance management strategies are developed. The characterization of Single-Photon Avalanche Diodes demonstrates their suitability for quantum communication, particularly in quantum key distribution and asynchronous heralded photon sources, with pathways for further improvements in speed and integration. Building on these detector technologies, a proof-of-principle integrated quantum key distribution system based on the BB84 protocol is presented. The system incorporates time-bin encoding, decoy-state methods, and photonic integrated circuits for both transmitter and receiver. Key challenges, such as chromatic dispersion and interferometer stability, are addressed through novel circuit and system-level designs. System-level testing and field deployment validate the feasibility of compact, high-performance integrated quantum key distribution implementations. Finally, the thesis explores quantum random number generation through semi-device-independent protocols. An experimental homodyne-based SDI-QRNG is realized, supported by custom transimpedance amplifier design and photonic integrated circuit integration. The setup achieves high bandwidth, strong quantum-to-classical noise separation, and stable operation, enabling practical random number generation rooted in fundamental quantum processes. Overall, this work advances the development of integrated quantum technologies by improving room-temperature single-photon detection, demonstrating scalable QKD prototypes, and implementing a high-speed QRNG. Together, these contributions pave the way toward secure, integrated quantum communication systems and practical quantum information applications ready to deploy in real world networks.
Quantum key distribution (QKD) is moving from laboratory demonstrations toward network deployment, and integrated photonic chips provide a hardware route for compact, stable and scalable systems. This review summarizes progress in integrated photonic chips for QKD from protocol requirements to deployable systems. It first examines how decoy-state BB84, measurement-device-independent QKD (MDI-QKD), twin-field QKD (TF-QKD), continuous-variable QKD (CV-QKD) and device-independent QKD (DI-QKD) constrain chip metrics such as loss, modulation accuracy, state indistinguishability, phase stability, synchronization and security monitoring. It then compares planar lightwave circuit (PLC), silicon photonics, silicon nitride, thin-film lithium niobate, indium phosphide (InP) and heterogeneous platforms in terms of routing loss, modulation speed, stable interference, source integration and detector interfaces. Transmitter and receiver architectures, coherent detection, single-photon detection interfaces and on-chip monitoring are discussed as system-level building blocks. The review further analyses phase stability, packaging coupling, thermal management, polarization control, network coexistence and reliability, emphasizing that deployable QKD chips must remain calibratable and compatible with security models under realistic operation. Finally, system demonstrations, network deployment and practical security are discussed within a unified evaluation framework. Throughout, we argue that integration benefits QKD only when compact routing, stable interference, calibration access and manufacturable packaging jointly keep the device inside the assumptions of its security proof; accordingly, chip performance should be judged by mapped, calibratable security parameters rather than by integration density alone.
Quantum communication promises unconditional security by leveraging the fundamental laws of quantum physics, which make eavesdropping detectable through the disturbance it introduces in quantum states. A cornerstone of this technology is quantum key distribution (QKD), enabling the distribution of a shared secret key between distant users with information- theoretic security, rather than relying on assumptions about an eavesdropper’s computational power, as in classical cryptography. However, current QKD systems rely largely on bulk-optical solutions, which limits scalability, stability, and integration into existing telecommunication infrastructures. Photonic integrated circuits (PICs) offer a promising platform to overcome these challenges by providing compact, stable, and CMOS-compatible architectures. This PhD work investigates integrated photonic platforms for practical quantum communication at telecommunication wavelengths, with a focus on demonstrating QKD protocols across three different encoding schemes: time-bin, frequency-bin, and path. First, a time-bin QKD receiver using a borosilicate-glass integrated imbalanced Mach–Zehnder interferometer (iMZI) is developed and compared with a fiber-based receiver, showing enhanced phase stability and improved long-distance secure key rates. Next, frequency-bin entanglement-based QKD is implemented using silicon microring resonators, demonstrating high-visibility quantum interference and active phase-stabilization techniques. Finally, a chip-to-chip path-entangled QKD link is realized using silicon photonic spiral sources, representing a crucial step toward fully integrated quantum transceivers. Across these experiments, this PhD thesis establishes a unified experimental framework for integrated QKD and evaluates performance in terms of quantum bit error rate, secure key rate, and system stability under realistic operating conditions. Together, the results provide a proof-of-concept demonstration of scalable, high-performance quantum communication using PIC technology, advancing toward practical deployment in future quantum networks and laying foundations for multidimensional and fully integrated quantum communication nodes.
Quantum Key Distribution (QKD) offers a revolutionary method for achieving information-theoretic security in communication systems by leveraging quantum mechanical principles. With foundational protocols like BB84 and newer innovations such as phase-matching and device-independent QKD, the field has rapidly progressed from theoretical constructs to real-world prototypes. Recent advancements in integrated photonics, high-speed key generation, and satellite-based systems suggest a transformative potential for global cybersecurity infrastructure. However, significant challenges remain in extending secure communication distances, ensuring practical implementation security, reducing cost and size of components, and integrating QKD into existing network architectures. This paper reviews the state-of-the-art in QKD, discusses emerging trends such as chip-based and layered QKD systems, evaluates satellite and free-space deployments, and examines the practical limitations and solutions for long-distance and high-rate secure communications. It concludes by highlighting future directions including standardization, hybrid classical-quantum infrastructures, and software-defined QKD networks.
Quantum key distribution (QKD) offers the highest possible levels of communication secrecy. Using the laws of quantum mechanics, QKD protocols allow two distant parties to establish symmetric encryption keys that can be proven information theoretically secure. In order to make this technology accessible to a wide range of sectors, it is essential to address the questions of cost, volume production and compatibility with standard Telecom/Datacom infrastructures. While over the last few years, a number of works were devoted to the demonstration of photonic integrated circuits for quantum communications, a practical solution to interface these chips in a complete system remained an elusive goal. We review our efforts in integrating the core optical functions of quantum key distribution onto quantum photonic chips and in demonstrating the first standalone photonic integrated QKD system. Our approach tackles various system integration challenges related to packaging, optoelectronic design and power consumption. The quantum hardware is assembled in pluggable interconnects that guarantee efficient thermal management and forward compatibility of a same host electronics with successive generations of chips. Autonomous operation and long-term stability are demonstrated in realistic operation conditions. Our work offers new pathways for practical implementations of QKD and its viable deployment at large scales.