Telecom-compatible, affordable and scalable quantum technologies
Nicola Montaut, Piotr Roztocki, Mario Chemnitz, Stefania Sciara, Benjamin MacLellan, Bennet Fischer, Y. Jestin, Luis Romero Cortés, Yanbing Young Zhang, José Azaña, Roberto Morandotti, Sai T. Chu, David Moss, Christian Reimer, Michael Kues, Brent E. Little, Hao Yu, Zhiming Wang, Lucia Caspani, Benjamin Wetzel, William J. Munro, Sebastian Loranger, Raman Kashyap, Alfonso Carmelo Cino
The realistic implementation of quantum architectures relies on the development of scalable, resource-efficient platforms that are compatible with CMOS technologies as well as fiber networks. This work demonstrates novel schemes utilized for time-/frequency-bin entanglement generation and processing by leveraging existing telecommunications and integrated photonics infrastructures.
The realistic implementation of quantum architectures relies on the development of scalable, resource-efficient platforms that are compatible with CMOS technologies as well as fiber networks. This work demonstrates novel schemes utilized for time-/frequency-bin entanglement generation and processing by leveraging existing telecommunications and integrated photonics infrastructures.
Quantum technologies harness nonclassical features of particles, here, photons, to develop novel, efficient, and precise devices for information processing applications. Superposition, entanglement, as well as the coherent manipulation of quantum states are at the heart of the second quantum revolution (quantum 2.0) which targets the development of secure cryptographic systems, complex computation protocols, and more. Emerging quantum architectures rely on the realistic implementation of photonic schemes which are scalable, resource-efficient, and compatible with CMOS technologies as well as fiber networks. This work demonstrates current schemes utilized for time-/frequency-bin entanglement generation and processing by leveraging existing telecommunications and integrated photonics infrastructures.
Quantum photonic resources are critical for advanced applications such as quantum computation, communication, and information processing. Efficient generation and detection of quantum states, as well as reliable photon manipulation techniques, are essential for the development of practical quantum technologies. Integrated photonic platforms offer attractive solutions due to their stability, small device footprint, and improved power efficiencies. However, optical loss and environmental noise hinder their capability to transmit, measure, and detect quantum states with high accuracies. To tackle these limitations, we have developed robust solutions for quantum signal processing by leveraging infrastructures from telecommunications and integrated photonics. These approaches focus on the use of silicon-based photonic sources for entanglement generation in the time and frequency degrees of freedom, as well as chip- and fiber-based architectures for entanglement verification via quantum interference and tomography measurements. Our photonic schemes allow for high-dimensional entanglement processing, demonstrating their versatility in developing scalable and cost-efficient quantum signal processing platforms.
The development of integrated photonic systems, both on-chip and fiber-based, has transformed quantum photonics by replacing bulky, fragile free-space optical setups with compact, efficient, and robust circuits. Photonic platforms incorporating fiber-connected sources of correlated and entangled photon pairs offer practical advantages, such as operation at room temperature, efficient integration with telecom infrastructure, and compatibility with mature and efficient semiconductor fabrication processes for cost-effective and large-scale optical circuits. The stability and scalability of integrated quantum photonics platforms have facilitated the generation and processing of quantum information in the temporal domain within a single spatial mode. Time-bin encoded states, known for their robustness against decoherence and compatibility with existing fiber-optic infrastructure, have shown to be an efficient paradigm for advanced applications like quantum secure communication, information processing, spectroscopy, imaging, and sensing. This review examines recent advancements in fiber- and chip-based platforms for generating non-classical states and their applications as quantum state processors in the time domain. We discuss the generation of pulsed quantum frequency combs using microring resonators and intra-cavity mode-locked laser schemes, enabling co- and cross-polarized quantum photonic states. Additionally, the versatility of these resonator chips for entanglement generation is emphasized, including two- and multi-photon time-bin entangled schemes. We highlight the development of time-bin entanglement analyzers in fiber architectures, featuring ultrahigh stability and post-selection-free capabilities, which enable precise and efficient characterization of two- and higher-dimensional time-bin entanglement. We also review scalable on-chip schemes for quantum key distribution, demonstrating low quantum bit error rates and compatibility with higher-dimensional quantum communication protocols. Further, methods for enhancing temporal resolution in detection schemes, crucial for time-bin encoding, are presented, such as the time-stretch sampling technique using electro-optic modulation. These innovations, relying on readily available, telecom-based fiber-optic components, provide practical, scalable, and cost-effective solutions for advancing quantum photonic technologies. Looking forward, time-bin encoding is expected to play a pivotal role in the advancement of quantum repeaters, distributed quantum networks, and hybrid light-matter systems, advancing the realization of globally scalable quantum technologies.
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.