| Quantum communication | |
|---|---|
| Name | Quantum communication |
| Type | Communication technology |
| Inventor | Charles H. Bennett; Gilles Brassard; developments by Artur Ekert and others |
| Introduced | 1980s |
| Country | International |
| Related | Quantum cryptography; Quantum information theory; Quantum computing |
Quantum communication
Quantum communication is the use of quantum mechanical systems to transmit, process, or secure information. Grounded in the principles of Quantum mechanics such as Quantum entanglement and superposition, it promises provable security and new paradigms for distributed computation. The field matters within Quantum physics because it translates foundational concepts into operational technologies with implications for national infrastructure, science policy, and civilian industry.
Quantum communication emerges directly from the mathematical and experimental structure of Quantum theory. It builds on quantum states of photons, atoms, or solid-state qubits to encode information in degrees of freedom like polarization or phase. The subject connects closely to Quantum information theory and experimental programs at institutions such as MIT, University of Oxford, University of Waterloo (Perimeter Institute and IQC), Chinese Academy of Sciences, and national laboratories like National Institute of Standards and Technology (NIST). Seminal theoretical work includes the 1984 BB84 protocol by Charles H. Bennett and Gilles Brassard and the 1991 Ekert protocol by Artur Ekert, linking cryptographic security to Bell inequalities and tests devised by John Bell.
Core quantum principles underpinning the field are Quantum entanglement, superposition, and the No-cloning theorem. Entanglement—demonstrated in experiments by Alain Aspect and later groups—enables nonclassical correlations used in teleportation and device-independent protocols. Superposition permits encoding of qubits in quantum states; measurement collapses these superpositions, producing the characteristic tradeoffs exploited by quantum key distribution. The no-cloning theorem, proved in the 1980s and often attributed in protocol contexts to works by Wootters and Zurek, prevents perfect duplication of unknown quantum states and forms the basis for provable eavesdropper detection. Complementary principles, including Quantum decoherence and error models studied in Quantum error correction, set limits that practical systems must manage.
Protocols translate principles into tasks. Quantum key distribution (QKD) such as BB84 and E91 provide information-theoretic secure key agreement. Quantum teleportation—first demonstrated in experiments by groups including Anton Zeilinger—allows transfer of an unknown qubit state using entanglement and classical communication. Superdense coding enables transmission of two classical bits via one entangled qubit pair. Security proofs draw upon Information-theoretic security and resources like entanglement measures; notable theoretical contributors include Peter Shor and John Preskill for security analysis and for establishing connections to Quantum error correction and channel capacities such as the Holevo bound.
Photon-based systems dominate long-distance quantum links, using sources like parametric down-conversion or single-photon emitters from NV centers and quantum dots. Free-space experiments include satellite links pioneered by projects such as Micius from the Chinese Academy of Sciences; fiber-optic deployments have been advanced by companies like ID Quantique and consortia in Europe, Japan, and the United States. Solid-state platforms (superconducting qubits at IBM, Google Quantum AI, and Rigetti Computing) and trapped-ion systems (e.g., IonQ) contribute to network node designs. Key enabling technologies include integrated photonics, single-photon detectors (avalanche photodiodes, superconducting nanowire detectors), quantum random number generators, and high-fidelity quantum memories.
Security in quantum communication rests on both physical assumptions and mathematical proofs. QKD can offer unconditional security under idealized assumptions; practical security addresses side-channel attacks, source imperfections, and detector loopholes. Device-independent QKD leverages violations of Bell's theorem to relax device trust, while composable security frameworks ensure secure integration with classical cryptography. Fundamental limits include channel capacities (for example, Shannon limit analogues in quantum channels) and constraints from decoherence and loss; theoretical bounds are studied via the Quantum capacity and entropic inequalities.
Scaling to continental or global distances requires architectures combining point-to-point links, trusted nodes, and quantum repeaters. Quantum repeaters mitigate loss and decoherence by using entanglement swapping, purification, and quantum error correction; foundational proposals include work by H.-J. Briegel and collaborators. Network demonstrations such as metropolitan QKD testbeds in Geneva, Beijing, and Tokyo show hybrid topologies integrating classical control planes with quantum links. Standardization and interoperability efforts involve organizations like the International Telecommunication Union (ITU) and national standards bodies.
Applications include secure communications for government and finance, distributed quantum computing, clock synchronization, and quantum-enhanced sensing. Challenges are technological—improving quantum memory times, reducing loss, and controlling noise—and organizational, requiring investment in infrastructure and skilled personnel. Future directions emphasize integration with classical cryptography (post-quantum and hybrid models), deployment of quantum satellite constellations, development of fault-tolerant quantum repeaters, and policy frameworks to ensure resilient, sovereign communications. Sustained collaboration among universities, national labs, and industry—supported by stable policy and funding—will determine whether quantum communication strengthens national security and preserves trusted communications infrastructure.
Category:Quantum information science Category:Quantum communication