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| Quantum entanglement | |
|---|---|
| Name | Quantum entanglement |
| Field | Quantum physics |
| Discovered | 1935 |
| Discoverers | Albert Einstein, Boris Podolsky, Nathan Rosen |
| Notable experiments | Bell test experiments, Aspect experiment |
Quantum entanglement is a quantum phenomenon in which the quantum states of two or more particles become correlated so that the state of each particle cannot be described independently of the others. It underpins predictions and technologies in Albert Einstein-era debates and modern efforts by institutions such as CERN, IBM, Google (company), National Institute of Standards and Technology for quantum information processing. Entanglement plays a central role in protocols developed by groups at University of Oxford, Massachusetts Institute of Technology, Harvard University, and University of Cambridge.
Entanglement emerges when systems prepared by laboratories like Bell Laboratories, Los Alamos National Laboratory, or Max Planck Society interact or undergo joint creation processes in setups used by researchers at Caltech and Stanford University. The phenomenon is characterized by correlations tested in experiments associated with John Bell-inspired inequalities and implementations by teams at Ecole Normale Supérieure and École Polytechnique. Applications envisioned by companies such as Microsoft and Intel and projects at DARPA include secure communication and sensing.
Early thought experiments by Albert Einstein, Boris Podolsky, and Nathan Rosen questioned completeness of theories in 1935, prompting commentary by Erwin Schrödinger and debate across institutions including University of Vienna and Princeton University. Later theoretical advances by John Bell led to inequalities tested in experiments by groups led by Alain Aspect and by researchers at University of Geneva and Weizmann Institute of Science. Cold-war era labs such as Bell Laboratories and collaborations spanning University of Vienna and University of Innsbruck further refined techniques that informed enterprises at Siemens and consortia like European Organization for Nuclear Research.
Quantum entanglement is formalized within the mathematical structure developed in texts from Paul Dirac, John von Neumann, and Werner Heisenberg, using tensor-product Hilbert spaces and density operators employed by theorists at Institute for Advanced Study and Cambridge University Press authorship. Bell's theorem by John Bell provides constraints distinguishing entangled states from local hidden-variable models considered by David Bohm and critiqued by figures connected to University of Copenhagen and University of Edinburgh. Quantum information theory, advanced by researchers like Charles Bennett, Peter Shor, and Gilles Brassard, defines measures such as entanglement entropy and concurrence discussed in literature published by Oxford University Press and taught at Massachusetts Institute of Technology.
Entanglement has been demonstrated in optical tests by teams at Laboratoire Kastler Brossel, Rutherford Appleton Laboratory, and National Institute of Standards and Technology. Landmark Bell tests include the Aspect experiment and loophole-closed trials by groups at Delft University of Technology, University of Vienna, and NIST. Matter-based entanglement experiments use systems developed at IBM, IonQ, and groups at University of Oxford and University of Cambridge, while space-based demonstrations were led by projects like Micius (satellite) and collaborations involving Chinese Academy of Sciences.
Entanglement enables protocols such as quantum teleportation demonstrated at California Institute of Technology and quantum key distribution implemented by companies like ID Quantique and groups at Toshiba Research Europe. Quantum computing efforts at Google (company), IBM, Microsoft, and startups like Rigetti Computing rely on entanglement for algorithms including those by Peter Shor and Lov Grover. Quantum sensing and metrology projects associated with National Institute of Standards and Technology and European Space Agency exploit entanglement for enhanced precision in clocks and interferometry used in collaborations with Max Planck Institute for Quantum Optics.
Entanglement raises foundational questions discussed in conferences at Perimeter Institute for Theoretical Physics, Santa Fe Institute, and forums involving scholars from Harvard University and Princeton University. It challenges intuitions traced to Albert Einstein's criticisms and has motivated alternative approaches explored by Hugh Everett III, David Bohm, and contemporary researchers at University of Oxford and University of Cambridge. Debates about nonlocality, realism, and causality reference experiments by Alain Aspect and theorems by John Bell and draw commentary from philosophers at London School of Economics and legal-ethical discussions in venues like United Nations forums on emerging technologies.
Scalability and error correction for entanglement in quantum processors being developed at Google (company), IBM, Microsoft, and Intel remain major engineering hurdles, as do decoherence issues studied at Lawrence Berkeley National Laboratory and Argonne National Laboratory. Questions about resource quantification and operational witnesses engage researchers affiliated with Perimeter Institute for Theoretical Physics, Institute for Quantum Computing, and universities such as University of Waterloo and University of Bristol. Broader societal and policy dimensions have been raised in dialogues at World Economic Forum and by agencies including National Science Foundation and European Commission.