Quantum networking is the technology and research field concerned with connecting quantum devices so that quantum information, entanglement or other quantum resources can be distributed between physically separated locations. A quantum network differs from an ordinary computer network because the information being transported or shared can be a quantum state, and quantum states cannot generally be copied or amplified in the same way as classical data.
A quantum network can contain quantum processors, quantum memories, quantum sensors, photonic interfaces, quantum transducers, measurement systems and classical control infrastructure. Its purpose may be to connect quantum computers, distribute entanglement, support quantum communication protocols, enable distributed quantum computation, synchronise quantum sensors or provide cryptographic capabilities such as quantum key distribution. Quantum networking therefore encompasses more than simply transmitting individual photons through optical fibre. A mature network must address state preparation, transmission, storage, synchronisation, error management, routing, measurement, classical coordination and interoperability. The long-term concept is sometimes described as a quantum internet, but a quantum network can be much smaller and more specialised than a global quantum internet.
Entanglement is a central resource in many quantum-network architectures. Two distant quantum systems can be prepared in an entangled state such that their measurement outcomes exhibit correlations that cannot generally be reproduced by independent classical states. Quantum teleportation uses shared entanglement together with classical communication to transfer an unknown quantum state from one location to another without physically transporting the original state itself. The protocol does not permit faster-than-light communication because classical information must accompany the entanglement-assisted process.
Quantum teleportation is therefore better understood as a state-transfer protocol rather than science-fiction-style transportation of matter. Entanglement distribution is also important for distributed quantum computing and quantum sensing. Establishing high-quality entanglement between distant nodes is technically difficult because quantum states are fragile and optical losses accumulate rapidly over distance. The quality, rate and fidelity of entanglement therefore become key network performance measures alongside conventional concepts such as latency and throughput.
Direct transmission through optical fibre is practical over limited distances but suffers from photon loss. Classical communication networks overcome attenuation using amplifiers or repeaters that measure and regenerate signals, but an ordinary amplifier cannot simply copy an arbitrary unknown quantum state because of the no-cloning theorem. Quantum repeaters are intended to address this problem through a sequence of shorter entanglement-generation links. Each segment can establish entanglement, and entanglement swapping can combine neighbouring links into longer-distance entanglement.
Quantum memories can store quantum states or entanglement while other parts of the network are prepared. Entanglement purification can, under appropriate conditions, improve the fidelity of shared entanglement by consuming multiple lower-quality entangled pairs to produce fewer higher-quality pairs. These mechanisms form the conceptual foundation of long-distance quantum networking, although building practical repeaters with sufficiently good memories, interfaces, loss rates and operation speeds remains a major engineering challenge.
Quantum networks require a classical control plane as well as quantum channels. Classical communication coordinates timing, heralding signals, measurement results, authentication, routing decisions and error-processing operations. Quantum and classical information therefore interact operationally even when the quantum channel carries the protected quantum states. Synchronisation is particularly important because photons may travel through different paths and quantum operations can depend on precise temporal relationships.
Network nodes need interfaces capable of converting between physical forms of quantum information when different hardware platforms are connected. For example, a quantum processor may use superconducting circuits while a communication link uses optical photons, creating a requirement for efficient microwave-to-optical or equivalent transduction. This makes quantum networking partly an interoperability problem. Network architectures may therefore include specialised photonic interfaces, quantum memories and transducers that allow heterogeneous quantum technologies to participate in a common communication system.
Quantum networking has several distinct application areas. Quantum key distribution can use quantum channels to establish cryptographic keys between distant parties. Distributed quantum computing could allow separate quantum processors to cooperate by sharing entanglement and performing non-local operations, potentially reducing the need to build a single enormous processor. Quantum sensor networks could connect geographically separated sensors so that correlations between measurements provide capabilities unavailable to isolated sensors. Networked quantum clocks may support highly precise timing comparisons.
Scientific experiments could distribute entanglement between laboratories to investigate fundamental physics or improve measurement techniques. These applications have different technical requirements. A QKD network may prioritise secure key generation and authenticated classical communication, whereas distributed quantum computing requires high-fidelity entanglement, reliable quantum memories and extremely accurate operations. Consequently, there is no single universal quantum-network architecture optimised for every use case.
Quantum networking should be distinguished from quantum computing and quantum communication. Quantum computing processes quantum information locally within a processor or collection of processors. Quantum communication concerns the transmission or exchange of quantum information and includes point-to-point protocols. Quantum networking adds a system-level perspective involving multiple interconnected nodes, network resources and coordination mechanisms. It should also be distinguished from classical networking that merely transports encrypted classical data.
A network carrying a classical ciphertext generated by a quantum-resistant algorithm is not necessarily a quantum network. Similarly, a QKD link can be considered a quantum communication system, while a larger infrastructure connecting many quantum nodes and distributing entanglement constitutes a quantum network. The term “quantum internet” generally refers to a much more ambitious network architecture capable of distributing quantum information and entanglement at large scale, but there is no requirement that every quantum network be global or support every conceivable quantum protocol.
The principal limitations of quantum networking arise from loss, decoherence, imperfect devices, memory lifetime, interface efficiency and the difficulty of maintaining entanglement over distance. Fibre attenuation means that directly transmitting single photons becomes increasingly inefficient as distance increases. Quantum memories must preserve coherence long enough for network operations to complete, yet storing quantum states reliably is difficult. Repeater protocols can require large numbers of physical resources and complex coordination.
Network security also has specialised considerations because quantum nodes can be attacked physically or electronically, and protocol-level security does not automatically secure the classical control infrastructure. Routing quantum information is different from routing ordinary packets because quantum states cannot simply be duplicated and copied into multiple paths. Research therefore examines entanglement routing, resource scheduling, network coding, quantum error correction, fault-tolerant communication and architectures for heterogeneous nodes.
Quantum networking is currently a developing technological field rather than a universally deployed replacement for the classical Internet. Experimental networks have demonstrated forms of entanglement distribution, quantum teleportation, QKD and interconnected quantum devices over laboratory, metropolitan and longer-distance links. The long-term research objective is to integrate quantum processors, memories and communication systems into networks capable of distributing entanglement reliably and performing useful distributed quantum tasks.
Achieving that objective requires progress in quantum hardware, photonics, error correction, networking protocols, transduction, control electronics and standardisation. The field's significance comes from treating quantum information as a network resource rather than something confined to one physical machine. If scalable quantum networking becomes practical, it could connect specialised quantum processors and sensors, support new cryptographic architectures and enable distributed quantum applications that cannot be implemented efficiently by isolated devices alone.
