| quantum teleportation | |
|---|---|
| Name | Quantum teleportation |
| Discovered | 1993 |
| Discoverers | Charles Bennett, Gilles Brassard, Claude Crépeau, Richard Jozsa, Asher Peres, William Wootters |
| Field | Quantum mechanics / Quantum information |
quantum teleportation
Quantum teleportation is a protocol that transfers the quantum state of a particle from one location to another without moving the particle itself, using quantum entanglement and classical communication. It is a central primitive in quantum information theory and underpins proposed technologies such as quantum computing networks and quantum key distribution systems, with deep implications for foundations of quantum mechanics.
Quantum teleportation was first described in a landmark 1993 paper by Bennett et al. and has since become a cornerstone of experimental and theoretical work in quantum information science. The protocol demonstrates the operational power of quantum entanglement and highlights the role of classical communication together with nonlocal correlations to achieve reliable state transfer. Its significance extends to enabling distributed quantum computation architectures, secure communications via quantum cryptography, and tests of nonlocality exemplified by experiments related to the Bell inequalities.
The protocol relies on several core concepts in quantum mechanics: the superposition principle, measurement-induced collapse, and entanglement. A maximally entangled resource, typically a Bell state (also called an Einstein–Podolsky–Rosen pair or EPR pair), is shared between sender (often named Alice) and receiver (Bob). Alice performs a joint measurement in the Bell basis on the unknown state and her half of the entangled pair, producing classical outcomes that she transmits to Bob. Bob applies a unitary correction conditioned on that classical information to reconstruct the original quantum state. Theoretical analysis uses tools from quantum channel theory, quantum fidelity, and density matrix formalism, and is closely related to concepts such as no-cloning theorem and quantum error correction.
Initial demonstrations usedphotons produced by parametric down-conversion in nonlinear crystals at groups such as those led by Anton Zeilinger and Paul Kwiat. Subsequent experiments achieved teleportation of single-photon polarization states, time-bin qubits, and continuous-variable states in laboratories at University of Innsbruck, University of Vienna, University of Oxford, and NIST. Teleportation over increasing distances has been demonstrated in optical fiber links and free-space channels, including satellite-based experiments by the Micius mission operated by the Chinese Academy of Sciences. Implementations also span platforms such as trapped ions (e.g., work by Rainer Blatt's group), superconducting circuits at IBM, and nitrogen-vacancy centers in diamond explored at institutions like University of Stuttgart and Harvard University.
The canonical Bennett protocol teleports a single qubit using one EPR pair and two classical bits. Variants include continuous-variable quantum teleportation introduced by Samuel L. Braunstein and Kimble for Gaussian states using squeezed light and homodyne detection, and entanglement swapping which concatenates teleportation steps to create long-distance entanglement in quantum repeater proposals by H.-J. Briegel et al. Multipartite teleportation and teleportation-based quantum gate teleportation form building blocks of measurement-based quantum computing (cluster states) developed by Raussendorf and Briegel. Protocol security and resource accounting connect to quantum channel capacity and entanglement measures such as entanglement of formation and concurrence.
Practical teleportation faces limits from decoherence, finite entanglement fidelity, detector inefficiencies, and losses in transmission media. The requirement for a prior entangled pair and two-way classical communication enforces a causal structure: teleportation cannot be used for faster-than-light signaling, consistent with special relativity. Scaling to long distances requires quantum repeaters and entanglement purification protocols, which introduce complexity and demand quantum memories with long coherence times. Theoretical limitations include the impossibility of teleporting unknown states without destroying the original (related to the no-broadcasting theorem and no-cloning), and resource-cost tradeoffs captured in entropic bounds like the Holevo bound.
Quantum teleportation is a primitive for constructing distributed quantum networks and the proposed quantum internet architecture championed by researchers at institutions including Caltech, MIT, and University of Cambridge. It enables state transfer in modular quantum computer designs (e.g., superconducting or ion-trap modules), supports protocols for quantum secret sharing and delegated quantum computation, and underlies approaches to fault-tolerant gate teleportation in topological quantum computing proposals. Beyond technology, teleportation experiments probe foundational issues in quantum theory, such as contextuality, realism debates sparked by EPR, and tests of quantum nonlocality.
Quantum teleportation interfaces with a broad range of topics: it employs quantum optics techniques, connects to statistical mechanics via decoherence models, and informs quantum metrology when entanglement resources are distributed for sensing networks. It stimulates advances in materials and device engineering for solid-state qubits, superconducting qubits, and quantum-limited amplifiers. The field interacts with major programs and organizations like Quantum Technology Flagship initiatives in the European Union, research efforts at DARPA, and collaborative projects at national laboratories such as Los Alamos National Laboratory and Lawrence Berkeley National Laboratory.
Category:Quantum information Category:Quantum optics Category:Quantum mechanics