Communication
Quantum communication encompasses applications with different core advantages: security-focused applications like quantum key distribution (QKD) and quantum cryptographic protocols, as well as capability-focused applications like quantum teleportation for transmitting quantum states, distributed quantum computing networks and quantum sensor arrays. In practice, current deployments are predominantly QKD systems which facilitate and ensure the confidentiality, integrity and authenticity of data communications.
Optical realisation
Optical realisation remains a highly specialised niche field within quantum communication. It comprises the technical adaptations and the physical components and devices to improve stability, efficiency and error rates in transmitting quantum information using optical systems. These systems use photons (particles of light) to generate, manipulate, transmit and measure quantum information.
Quantum memories
Quantum memories are capable of storing quantum states with long coherence times, essential for long-distance communication (e.g. satellite-based networks or networks with non-trusted nodes). As in classical memories, their function is to serve as nodes that can store and retrieve quantum information on demand. These components are critical for overcoming the signal degradation that currently still limits long-distance communication in quantum networks, primarily through their (future) role in quantum repeaters and switches.
Quantum key distribution (QKD)
QKD allows [two parties] to agree on a shared secret (such as a cryptographic key) based on quantum states. It is typically achieved by using photons through optical channels. A key feature of QKD technology is its ability to detect tampering with the underlying quantum states.
Information networks
An information network is a system that collects, processes, transmits and disseminates information and data by connecting, for example, computers. Like a classical computer network which requires transmission means, hubs, servers, routers and switches, network architectures linking quantum devices (computers, sensors) via quantum states (typically photons) require special network components that can store, transmit and route quantum-based data. These components should, in the future, form the backbone of a “quantum internet”.