Editing Bell's theorem (section)

=== Non-local hidden variables ===

Most advocates of the hidden-variables idea believe that experiments have ruled out local hidden variables.{{refn|group=note|[[E. T. Jaynes]] was one exception,<ref name="E.T. Jaynes 1989">{{Cite book |year=1989 |last1=Jaynes |first1=E. T. |title=Maximum Entropy and Bayesian Methods |chapter=Clearing up Mysteries — the Original Goal |pages=1–27 |url=http://bayes.wustl.edu/etj/articles/cmystery.pdf |doi=10.1007/978-94-015-7860-8_1 |isbn=978-90-481-4044-2 |citeseerx=10.1.1.46.1264 |access-date=2011-10-18 |archive-date=2011-10-28 |archive-url=https://web.archive.org/web/20111028131916/http://bayes.wustl.edu/etj/articles/cmystery.pdf |url-status=live }}</ref> but Jaynes' arguments have not generally been found persuasive.<ref name="Gill2002">{{cite book|chapter=Time, Finite Statistics, and Bell's Fifth Position|first=Richard D.|last=Gill|pages=179–206|title=Proceedings of the Conference Foundations of Probability and Physics - 2 : Växjö (Soland), Sweden, June 2-7, 2002 |volume=5|publisher=Växjö University Press|date=2002|arxiv=quant-ph/0301059 }}</ref>}} They are ready to give up locality, explaining the violation of Bell's inequality by means of a non-local [[hidden variable theory]], in which the particles exchange information about their states. This is the basis of the [[Bohm interpretation]] of quantum mechanics, which requires that all particles in the universe be able to instantaneously exchange information with all others. One challenge for non-local hidden variable theories is to explain why this instantaneous communication can exist at the level of the hidden variables, but it cannot be used to send signals.<ref>{{Cite journal |last1=Wood |first1=Christopher J. |last2=Spekkens |first2=Robert W. |author-link2=Robert Spekkens |date=2015-03-03 |title=The lesson of causal discovery algorithms for quantum correlations: causal explanations of Bell-inequality violations require fine-tuning |url=https://iopscience.iop.org/article/10.1088/1367-2630/17/3/033002 |journal=[[New Journal of Physics]] |volume=17 |issue=3 |pages=033002 |arxiv=1208.4119 |bibcode=2015NJPh...17c3002W |doi=10.1088/1367-2630/17/3/033002 |s2cid=118518558 |issn=1367-2630}}</ref> A 2007 experiment ruled out a large class of non-Bohmian non-local hidden variable theories, though not Bohmian mechanics itself.<ref>{{cite journal |doi=10.1038/nature05677 |title=An experimental test of non-local realism |year=2007 |last1=Gröblacher |first1=Simon |last2=Paterek |first2=Tomasz |last3=Kaltenbaek |first3=Rainer |last4=Brukner |first4=Časlav |author-link4=Časlav Brukner |last5=Żukowski |first5=Marek |last6=Aspelmeyer |first6=Markus |last7=Zeilinger |first7=Anton |author-link7=Anton Zeilinger |journal=[[Nature (journal)|Nature]] |volume=446 |issue=7138 |pages=871–5 |pmid=17443179|bibcode = 2007Natur.446..871G | arxiv= 0704.2529 |s2cid=4412358 }}</ref>

The [[transactional interpretation]], which postulates waves traveling both backwards and forwards in time, is likewise non-local.<ref>{{Cite journal|last=Kastner|first=Ruth E.|date=May 2010|title=The quantum liar experiment in Cramer's transactional interpretation|url=https://linkinghub.elsevier.com/retrieve/pii/S135521981000002X|journal=[[Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics]] |language=en|volume=41|issue=2|pages=86–92|arxiv=0906.1626|bibcode=2010SHPMP..41...86K|doi=10.1016/j.shpsb.2010.01.001|s2cid=16242184|access-date=2021-09-16|archive-date=2018-06-24|archive-url=https://web.archive.org/web/20180624053010/https://linkinghub.elsevier.com/retrieve/pii/S135521981000002X|url-status=live}}</ref>