| quantum communication | |
|---|---|
| Name | Quantum communication |
| Type | Communication technology |
| Invented | 20th century |
| Developer | IBM, Google, D-Wave, Xanadu, ID Quantique |
| Based on | Quantum mechanics, Quantum information theory |
| Application | Secure communication, quantum networking, distributed quantum computing |
quantum communication
Quantum communication is the study and application of information transfer using quantum mechanical systems, exploiting phenomena such as quantum entanglement and quantum superposition to encode, transmit and process information. It matters in the context of Quantum Physics because it enables tasks—most notably provably secure quantum cryptography and quantum networking—that are impossible or inefficient with classical channels, and it forms a bridge between foundational quantum theory and practical technologies like the quantum internet.
Quantum communication rests on the laws of quantum mechanics and the formalism of quantum information theory. Core primitives include preparation, manipulation and measurement of quantum states under unitary evolution and open-system dynamics described by quantum decoherence and quantum channels. Relevant theoretical results include the no-cloning theorem, which prohibits perfect copying of unknown quantum states, and the Holevo bound, which limits classical information extractable from quantum systems. Foundational experiments invoking Bell inequalities—following work by John Bell and implemented in laboratories such as Institut d'Optique and groups led by Alain Aspect—established nonlocal correlations that underpin entanglement-based communication protocols.
Information in quantum communication is typically encoded in a qubit or higher-dimensional qudit. Physical carriers include single photons in optical fibers or free space, trapped ions, superconducting qubits, quantum dots, and nitrogen-vacancy centers in diamond. Photonic implementations exploit degrees of freedom such as polarization, time-bin, phase and orbital angular momentum. State characterization uses quantum state tomography and verification employs methods like entanglement witnesses and Bell tests. Theoretical models often reference density matrix formalism and quantum operations described by Kraus operators.
Prominent protocols include BB84 (Bennett and Brassard 1984) and E91 (Ekert 1991) for quantum key distribution (QKD), quantum teleportation for state transfer, and superdense coding for enhanced classical capacity. Entanglement swapping is used in repeater-based networks, while entanglement distillation and quantum error correction protocols (e.g., Shor code, Steane code) maintain fidelity. Quantum repeaters combine entanglement purification and swapping to extend range. Algorithmic aspects intersect with quantum communication complexity and tasks like position-based cryptography. Notable theoretical contributions come from researchers such as Charles H. Bennett, Gilles Brassard, Artur Ekert, and Peter Shor.
Major experimental platforms and organizations include the European Union initiatives (e.g., Quantum Internet Alliance), national programs like U.S. National Quantum Initiative, and companies such as ID Quantique, Toshiba Research, MagiQ Technologies, and Quantum Xchange. Laboratory systems use single-photon detectors such as avalanche photodiodes and superconducting nanowire detectors, and sources like spontaneous parametric down-conversion and quantum dot emitters. Long-distance demonstration projects include satellite-based QKD by China National Space Administration's Micius satellite and fiber network trials in cities by telecoms like BT Group and Deutsche Telekom. Testbeds for distributed quantum processing are being developed by institutions such as MIT, University of Cambridge, University of Oxford, NIST and Zapata Computing collaborations.
Security derives from physical principles rather than computational assumptions. QKD schemes like BB84 and device-independent protocols based on Bell violations aim to provide information-theoretic security against eavesdroppers constrained by quantum laws. Security proofs employ composable frameworks and account for side channels, implementation flaws, and measurement-device-independent (MDI) approaches. Standards and certification bodies, including ETSI and ISO, are developing guidelines. Post-quantum cryptography research—led by groups at NIST—addresses classical algorithms resistant to quantum attacks, complementary to quantum-safe key distribution.
Practical quantum communication faces challenges: photon loss in fibers and free space, detector inefficiencies, decoherence, and limited entanglement distribution distance. Quantum repeaters remain experimentally demanding due to requirements for long-lived quantum memories and high-fidelity operations. Error management relies on quantum error correction, entanglement purification, and fault-tolerant designs. Scalability concerns intersect with classical network integration, routing, and synchronization, requiring advances in hardware and control software from vendors like Rigetti Computing and research consortia such as the Quantum Internet Alliance.
Applications include secure communications (QKD), distributed quantum computing, blind quantum computation, quantum-enhanced sensing networks, and clock synchronization. Architectures range from point-to-point QKD links to metropolitan quantum networks and envisioned global quantum internet topologies employing trusted nodes, quantum repeaters, and satellite relays. Emerging services and business models involve quantum-secure backbone links for finance and government, as pursued by companies such as BT Group and SK Telecom, and research demonstrations integrating classical telecom infrastructure with quantum channels.
Category:Quantum information science Category:Quantum optics