Editing Complementarity (physics) (section)

=== Debate following the lectures ===
{{Main | Bohr–Einstein debates}}

Complementarity was a central feature of Bohr's reply to the [[EPR paradox]], an attempt by Albert Einstein, [[Boris Podolsky]] and [[Nathan Rosen]] to argue that quantum particles must have position and momentum even without being measured and so quantum mechanics must be an incomplete theory.<ref name=":0">{{cite journal|first=Christopher A. |last=Fuchs |title=Notwithstanding Bohr: The Reasons for QBism |journal=Mind and Matter |volume=15 |pages=245–300 |year=2017 |arxiv=1705.03483 |bibcode=2017arXiv170503483F}}</ref> The [[thought experiment]] proposed by Einstein, Podolsky and Rosen involved producing two particles and sending them far apart. The experimenter could choose to measure either the position or the momentum of one particle. Given that result, they could in principle make a precise prediction of what the corresponding measurement on the other, faraway particle would find. To Einstein, Podolsky and Rosen, this implied that the faraway particle must have precise values of both quantities whether or not that particle is measured in any way. Bohr argued in response that the deduction of a position value could not be transferred over to the situation where a momentum value is measured, and vice versa.<ref>{{cite book|last=Jammer|first=Max|title=The Philosophy of Quantum Mechanics|publisher=John Wiley and Sons|year=1974|isbn=0-471-43958-4|author-link=Max Jammer}}</ref>

Later expositions of complementarity by Bohr include a 1938 lecture in [[Warsaw]]<ref name=":1">{{cite book|first=Niels |last=Bohr |author-link=Niels Bohr |chapter=The causality problem in atomic physics |title=New theories in physics |publisher=International Institute of Intellectual Co-operation |location=Paris |year=1939 |pages=11–38}}</ref><ref name="chevalley1999">{{cite book|first=Catherine |last=Chevalley |chapter=Why Do We Find Bohr Obscure? |title=Epistemological and Experimental Perspectives on Quantum Physics |editor-first1=Daniel |editor-last1=Greenberger |editor-first2=Wolfgang L. |editor-last2=Reiter |editor-first3=Anton |editor-last3=Zeilinger |publisher=Springer Science+Business Media |doi=10.1007/978-94-017-1454-9 |isbn=978-9-04815-354-1 |year=1999 |pages=59–74}}</ref> and a 1949 article written for a [[festschrift]] honoring Albert Einstein.<ref name="Bohr1949">{{cite book|title=Albert Einstein: Philosopher-Scientist|last=Bohr|first=Niels|publisher=Open Court|year=1949|editor=Schilpp|editor-first=Paul Arthur|editor-link=Paul Arthur Schilpp|chapter=Discussions with Einstein on Epistemological Problems in Atomic Physics|author-link=Niels Bohr}}</ref> It was also covered in a 1953 essay by Bohr's collaborator [[Léon Rosenfeld]].<ref>{{Cite journal|last=Rosenfeld|first=L.|date=1953|title=Strife about Complementarity|url=https://www.jstor.org/stable/43414997|journal=Science Progress (1933- )|volume=41|issue=163|pages=393–410|jstor=43414997 |issn=0036-8504}}</ref>