This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| entanglement swapping | |
|---|---|
| Name | Entanglement swapping |
| Field | Quantum information science |
| Introduced | 1993 |
| Related | Quantum teleportation, Bell state measurement, Quantum repeaters |
entanglement swapping Entanglement swapping is a protocol in which entanglement is created between two particles that have never interacted, by performing joint measurements on partner particles. Originating from theoretical work in the early 1990s, the protocol plays a central role in proposals for long-distance quantum communication and quantum networks, connecting advances associated with Artur Ekert, Charles H. Bennett, Gilles Brassard, Anton Zeilinger, and institutions such as Massachusetts Institute of Technology, University of Innsbruck, and Institute of Photonic Sciences. Its feasibility has been demonstrated in experiments involving groups at University of Vienna, National Institute of Standards and Technology, California Institute of Technology, and Tsinghua University.
Entanglement swapping links outcomes of Bell-type measurements to generate nonlocal correlations between distant systems, extending techniques from Bennett-led quantum teleportation studies and concepts related to the Einstein–Podolsky–Rosen paradox and John Bell's inequalities. The procedure underlies architectures proposed by teams at European Space Agency, Delft University of Technology, and National Aeronautics and Space Administration for quantum repeaters and satellite-based entanglement distribution, influenced by milestones like the Lo and Chau security analyses and demonstrations concurrent with efforts at IBM and Google research groups.
The formalism uses tensor-product Hilbert spaces and projective measurements defined originally in works associated with Werner Heisenberg, Paul Dirac, and modern expositions by researchers at Perimeter Institute and Centre for Quantum Technologies. A canonical derivation employs four-mode entangled states and a Bell state measurement drawing on algebra introduced by John von Neumann and later operationalized in protocols influenced by Bennett and Brassard. Foundational implications connect to thought experiments articulated by Albert Einstein, Boris Podolsky, Nathan Rosen, and later to nonlocality tests by Alain Aspect and loophole closures pursued by groups at Hiroshima University and University of Oxford.
Early laboratory realizations built on parametric down-conversion sources used in experiments at University of Innsbruck and University of Vienna, with detection technology developed in collaborations involving National Institute of Standards and Technology and companies like Thorlabs. Landmark field trials include fiber-based demonstrations by teams at Toshiba Research Europe, free-space links by groups at Micius (satellite)-affiliated projects and ground stations coordinated with Chinese Academy of Sciences, and metropolitan-scale networks developed by consortia including Jena-Optronik and Delft University of Technology. Implementations often combine superconducting nanowire single-photon detectors pioneered at NIST and integrated photonics approaches advanced at MIT and Tsinghua University.
Entanglement swapping is a building block for quantum repeaters proposed in architectures by researchers at Los Alamos National Laboratory and University of Cambridge, enabling quantum key distribution protocols inspired by Ekert, as well as multi-node quantum networks envisioned by teams at Intel and Xanadu. It supports distributed quantum computing schemata advocated in roadmaps from European Commission projects and testbeds deployed by consortia including National Science Foundation initiatives and collaborations with Aalto University. Practical applications extend to quantum metrology scenarios influenced by work at NIST and secure communication pilots with involvement from BT Group and Deutsche Telekom research units.
Extensions include entanglement swapping variants combined with entanglement purification studied by groups at Los Alamos National Laboratory and University of Geneva, hybrid protocols merging continuous-variable techniques developed at University of Tokyo and discrete-variable approaches from University of Oxford, and circuit-based realizations explored by teams at Google and IBM. Multi-photon and multi-node generalizations draw on cluster state and graph state formalisms advanced by Raussendorf and Hein, and integrated designs for quantum repeaters incorporate error-correction ideas from Peter Shor and fault-tolerance theory connected to work at California Institute of Technology and University of Waterloo.
Practical scaling faces decoherence and loss issues addressed in studies led by Lucien Hardy and engineering efforts at Toshiba Research Europe and Nokia Bell Labs, while security analyses relate to side-channel considerations evaluated by teams at Cryptography Research, Inc. and academic groups at Royal Holloway. Open questions include optimizing Bell-state measurement efficiencies pursued by NIST and improving quantum memory lifetimes targeted by research at Institute of Photonic Sciences and Max Planck Institute for Quantum Optics. Integration into global quantum networks requires collaboration across funding bodies such as European Research Council and national labs including Los Alamos National Laboratory and Argonne National Laboratory.