Editing Quantum entanglement (section)

=== Methods of creating entanglement ===
Entanglement is usually created by direct interactions between subatomic particles. These interactions can take numerous forms. One of the most commonly used methods is [[spontaneous parametric down-conversion]] to generate a pair of photons entangled in polarization.<ref name="horodecki2007">
{{cite journal
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 |title = Quantum entanglement
 |journal = Reviews of Modern Physics
 |arxiv=quant-ph/0702225
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}}</ref><ref name="Shadbolt2012">
{{cite journal
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 |last8=Thompson |first8=M. G.
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 |title=Generating, manipulating and measuring entanglement and mixture with a reconfigurable photonic circuit
 |journal=Nature Photonics
 |year=2012 |volume=6 |issue=1 |pages=45–59
 |arxiv=1108.3309 |doi=10.1038/nphoton.2011.283
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 }}</ref> Other methods include the use of a [[fibre coupler]] to confine and mix photons, photons emitted from decay cascade of the bi-exciton in a [[quantum dot]],<ref>{{cite journal |last=Akopian |first=N. |date=2006 |title=Entangled Photon Pairs from Semiconductor Quantum Dots |journal=Physical Review Letters |volume=96 |issue=2 |pages=130501 |arxiv=quant-ph/0509060 |bibcode=2006PhRvL..96b0501D |doi=10.1103/PhysRevLett.96.020501 |pmid=16486553 |s2cid=22040546 }}</ref> or the use of the [[Hong–Ou–Mandel effect]].<ref>{{cite journal|last1=Lee |first1=Hwang |last2=Kok |first2=Pieter |last3=Dowling |first3=Jonathan P. |author-link3=Jonathan Dowling |title=A quantum Rosetta stone for interferometry |journal=Journal of Modern Optics |volume=49 |number=14–15 |year=2002 |pages=2325–2338 |doi=10.1080/0950034021000011536 |arxiv=quant-ph/0202133|bibcode=2002JMOp...49.2325L}}</ref> Quantum entanglement of a [[elementary particle|particle]] and its [[antiparticle]], such as an electron and a [[positron]], can be created by partial overlap of the corresponding [[quantum wave function]]s in [[Hardy's paradox|Hardy's interferometer]].<ref name="Hardy1992">
{{cite journal
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 | title = Quantum mechanics, local realistic theories, and Lorentz-invariant realistic theories
 | journal = Physical Review Letters
 | volume = 68
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 | pages = 2981–2984
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 | year = 1992
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}}</ref><ref name="Georgiev2022">
{{cite journal
 | last1 = Georgiev | first1 = Danko
 | last2 = Cohen | first2 = Eliahu
 | title = Entanglement measures for two-particle quantum histories
 | journal = Physical Review A
 | volume = 106
 | number = 6
 | pages = 062437
 | doi = 10.1103/PhysRevA.106.062437
 | arxiv = 2212.07502
 | year = 2022
 | bibcode = 2022PhRvA.106f2437G
 | s2cid = 254685902
}}</ref> In the earliest tests of Bell's theorem, the entangled particles were generated using [[atomic cascade]]s.<ref name="Clauser"/>

It is also possible to create entanglement between quantum systems that never directly interacted, through the use of [[Quantum teleportation#Entanglement swapping|entanglement swapping]]. Two independently prepared, identical particles may also be entangled if their wave functions merely spatially overlap, at least partially.<ref>{{cite journal |last1=Lo Franco |first1=Rosario |last2=Compagno |first2=Giuseppe |date=14 June 2018 |title=Indistinguishability of Elementary Systems as a Resource for Quantum Information Processing |journal=Physical Review Letters |volume=120 |issue=24 |pages=240403 |arxiv=1712.00706 |bibcode=2018PhRvL.120x0403L |doi=10.1103/PhysRevLett.120.240403 |pmid=29957003 |s2cid=49562954}}</ref>