Quantum communication exploits the transmission of information encoded by single quanta or via the quantum mechanical effects superposition, interference, and entanglement. In addition to secure message transmission, quantum communication will include future capabilities for the distribution of entangled states in the areas of communication, sensor technology and computing and is therefore the basis for long-term developments in quantum technology as a whole. However, current applications of quantum communication are limited, mainly due to the degradation of quantum information during transmission via fiber optics or satellite. Advancing the underlying metrology for quantum communication is crucial to paving the way for robust and certified commercial quantum communication systems. The Optics division at PTB is involved in a number of projects and initiatives at national and European level to promote improved metrology for quantum communication.
Quantum communication exploits the transmission of information encoded by single quanta or via the quantum mechanical effects superposition, interference, and entanglement. In addition to secure message transmission, quantum communication will include future capabilities for the distribution of entangled states in the areas of communication, sensor technology and computing and is therefore the basis for long-term developments in quantum technology as a whole. However, current applications of quantum communication are limited, mainly due to the degradation of quantum information during transmission via fiber optics or satellite. Advancing the underlying metrology for quantum communication is crucial to paving the way for robust and certified commercial quantum communication systems. The Optics division at PTB is involved in a number of projects and initiatives at national and European level to promote improved metrology for quantum communication.
Industrial technologies based on the production, manipulation, and detection of single and entangled photons are emerging, and quantum key distribution via optical fibre is one of the most commercially-advanced. The National Physical Laboratory is developing traceable performance metrology for the quantum devices used in these technologies. This is part of a broader effort to develop metrological techniques and standards to accelerate the development and commercial uptake of new industrial quantum communication technologies based on single photons. This presentation will give an overview of the work carried out at NPL and within the wider European community, and highlight plans for the future.
Quantum Key Distribution, a fundamental component of quantum secure communication that exploits quantum states and resources for communication protocols, can future-proof the security of digital communications, when if advanced quantum computing systems and mathematical advances render current algorithmic cryptography insecure. A QKD system relies on the integration of quantum physical devices, as quantum sources, quantum channels and quantum detectors, in order to generate a true random (unconditionally secure) cryptographic key between two remote parties connected through a quantum channel. The gap between QKD implemented with ideal and real devices can be exploited to attack real systems, unless appropriate countermeasures are implemented. Characterization of real devices and countermeasure is necessary to guarantee security. Free-space QKD systems can provide secure communication to remote parties of the globe, while QKD systems based on entanglement are intrinsically less vulnerable to attack. Metrology to characterize the optical components of these systems is required. Actually, the “Optical metrology for quantum-enhanced secure telecommunication” Project (MIQC2) is steering the metrological effort for Quantum Cryptography in the European region in order to accelerate the development and commercial uptake of Quantum Key Distribution (QKD) technologies. Aim of the project is the development of traceable measurement techniques, apparatus, and protocols that will underpin the characterisation and validation of the performance and quantum-safe security of such systems, essential steps towards standardization and certification of practical implementations of quantum-based technologies.
For more than 100 years, researchers explore quantum physics, which led to major breakthroughs, such as the laser, being today in daily use. With the increased control that is gained in recent years over quantum systems, the current advances in quantum technologies allow the exploitation and distinct control of quantum phenomena such as superposition and entanglement. These quantum phenomena enable fundamental performance advantages over normal classical procedures. They can be used for example to realize quantum-enhanced metrology, where quantum systems show the increase in sensitivity for metrological tasks, such as length measurements, as it will be exploited in the next generation of gravitational wave detection systems. Moreover, quantum physics is foreseen to enable quantum computing which could accelerate computational tasks for certain specific problems and enable entirely novel solutions with applications in drug development, material design or climate change. However current quantum computing technology is still in a prove-of-concept demonstration phase as it requires to prove scalability to large-scale quantum systems. More conceptually and technologically advanced is the use of quantum phenomena in order to realize future-prove communication systems, that means communication techniques which cannot be decrypted by future advances in mathematical concepts or computing resources. Here prove-of-concept systems in optical fiber as well as in satellite configurations and even commercial devices already exist, which require however advances with respect to multi-user operation increased transmission rates and reduced complexity.
Quantum physics looks back at over a century of tradition and represents the foundation of metrology. The last twenty years of progress in science and technology have seen a tremendous increase in the level of control over quantum systems at the most elementary level. This development paves the way for novel applications of quantum technology with relevance for economy and potentially disruptive impact. With this potential comes the need to support the dynamic development with metrology for the emerging quantum industry to create trust, reliability, enable comparability and thus lay the foundation for a future quality infrastructure. The Quantum Technology Center (QTZ) at PTB is addressing this need for several quantum technologies. Examples include: Ion traps, as a hardware platform for quantum clocks, quantum sensors and quantum computers, have evolved to mature quantum devices which already made the step from a research object into an industrial product. Providing novel products for end users requires fair comparisons of these devices, consequently requiring standardized methods for testing and characterization. QTZ has successfully established a characterization setup for ion traps from industry and academia, providing a stable environment for reproducible and fair comparisons. Many quantum communication technologies, particularly quantum key distribution, operate within the single-photon domain, leveraging the non-cloning theorem to prevent eavesdropping by transmitting individual photons. QTZ contributes to the establishment of a robust foundation for standardized characterization and future certification activities, by offering testing facilities for key components, such as single-photon detectors, optical attenuators, isolators, and spectral filters. The precise clocked transport of single electrons has gained a lot of interest for the 2019 revised SI system as a unique and elegant way of a direct realization of the unit ampere. QTZ is developing single-electron pumps based on quantum dots, with the general objectives of robustness, reproducibility and scaling. In addition to their primary use in metrology, these universal devices can be of interest for applications in quantum technology, e.g. in quantum computing as so-called spin qubit shuttles, a connecting path over several µm in length between different qubits, enabling the scaling of complex multiple qubit systems. Across all fields, documentary standards, developed in an international consensus framework, are a fundamental part of a successful quantum technology ecosystem. PTB is actively contributing to the International IEC/ISO JTC3 and the European CEN/CENELEC JTC22. These activities are complemented by several projects in cooperation with industry. In this contribution, we will give an overview of our activities and discuss future challenges and opportunities of metrology for quantum technology and the emerging quantum industry.
Entanglement distribution is a fundamental building block of quantum communication networks, enabling the secure and reliable exchange of quantum information over long distances. Unlike classical communication, quantum networks exploit the unique properties of quantum entanglement to support applications such as quantum key distribution, quantum teleportation, distributed quantum computing, and networked quantum sensing. Although significant progress has been made in recent years, the efficient generation, transmission, and preservation of entangled states remain major research challenges due to photon loss, decoherence, and limitations in current communication infrastructure.This review provides a comprehensive overview of entanglement distribution in quantum communication networks, focusing on the technologies that enable practical implementation and the latest experimental developments. It discusses key approaches for generating and distributing entangled photons through optical fibers, free-space links, and satellite-based communication, together with supporting technologies such as quantum repeaters, quantum memories, and photonic devices. The review also examines recent experimental demonstrations that have advanced long-distance quantum communication while highlighting the technical barriers that must be overcome for large-scale deployment. Finally, emerging applications and future research directions are presented, including the development of scalable quantum networks, the quantum internet, and secure global communication systems. This review aims to provide researchers and students with a clear understanding of the current state of entanglement distribution and its growing role in next-generation quantum communication technologies.
Quantum communication and information networks offer unprecedented processing efficiency and security for data transfers. Technologies like quantum key distribution (QKD), quantum repeaters, quantum memory, and quantum entanglement sources are enabling technologies that ensure secure communication. QKD methods use quantum physics concepts to establish cryptographic keys, while quantum repeaters compensate for signal loss in fiber optic cables. Quantum memory enables storage and retrieval of quantum information, while quantum entanglement generators generate entangled photon pairs. Artificial intelligence and machine learning have significantly improved the efficacy and security of quantum communication. These methods can facilitate ultra-secure, reliable, large-scale communication and even a future quantum internet by analyzing quantum protocols and mitigating noise-induced errors. QKD protocols ensure secure communication channels, while quantum repeaters establish secure long-distance communication lines by mitigating signal loss. Traditional Internet technology is susceptible to surveillance due to Shannon's information theory and mathematics. The quantum internet (QI) uses satellite-based quantum communication and quantum cryptographic protocols for physical QI. Quantum entanglement sources fortify secure communication protocols, improving resistance to attacks. Quantum information networks (QINs) enhance computing, sensing, and security capabilities over extended distances. The development of reliable, robust communication systems depends on these technologies. Quantum-secured networks enhance urban security, smart management, and infrastructure protection by providing data privacy and facilitating secure data transmission, thereby facilitating robust infrastructure and technological development.