Editing Copenhagen interpretation (section)

{{Short description|Interpretation of quantum mechanics}}
{{Quantum mechanics|expanded=interpretations}}

The '''Copenhagen interpretation''' is a collection of views about the meaning of [[quantum mechanics]], stemming from the work of [[Niels Bohr]], [[Werner Heisenberg]], [[Max Born]], and others.<ref>See, for example:
*{{cite book|title=Letters on Wave Mechanics: Correspondence with H. A. Lorentz, Max Planck, and Erwin Schrödinger|isbn=9781453204689 |publisher=Philosophical Library/Open Road |year=2015 |editor-first=K. |editor-last=Przibram |translator-first=Martin J. |translator-last=Klein |orig-year=1967 |quote=the Copenhagen Interpretation of quantum mechanics, [was] developed principally by Heisenberg and Bohr, and based on Born's statistical interpretation of the wave function.}}
*{{cite book|editor-last1=Buckley |editor-first1=Paul |editor-last2=Peat |editor-first2=F. David |chapter=Leon Rosenfeld |title=A Question of Physics: Conversations in Physics and Biology |publisher=University of Toronto Press |year=1979 |pages=17–33 |jstor=10.3138/j.ctt15jjc3t.5 |quote=The Copenhagen interpretation of quantum theory, ... grew out of discussions between Niels Bohr and Werner Heisenberg...|last1=Buckley |first1=Paul |last2=Peat |first2=F. David |author3=Bohm |author4=Dirac |author5=Heisenberg |author6=Pattee |author7=Penrose |author8=Prigogine |author9=Rosen |author10=Rosenfeld |author11=Somorjai |author12=Weizsäcker |author13=Wheeler |isbn=9781442651661 }}
*{{cite book|last=Gbur |first=Gregory J. |author-link=Greg Gbur |title=Falling Felines and Fundamental Physics |publisher=Yale University Press |year=2019 |pages=264–290 |doi=10.2307/j.ctvqc6g7s.17 |s2cid=243353224 |quote=Heisenberg worked under Bohr at an institute in Copenhagen. Together they compiled all existing knowledge of quantum physics into a coherent system that is known today as the Copenhagen interpretation of quantum mechanics.}}</ref> While "Copenhagen" refers to the Danish city, the use as an "interpretation" was apparently coined by Heisenberg during the 1950s to refer to ideas developed in the 1925–1927 period, glossing over his disagreements with Bohr.<ref name="Faye-Stanford">{{Cite book|last=Faye|first=Jan|title=[[Stanford Encyclopedia of Philosophy]]|publisher=Metaphysics Research Lab, Stanford University|year=2019|editor-last=Zalta|editor-first=Edward N.|chapter=Copenhagen Interpretation of Quantum Mechanics|author-link=Jan Faye|chapter-url=https://plato.stanford.edu/entries/qm-copenhagen/}}</ref><ref name="camilleri2015">{{cite journal|first1=K. |last1=Camilleri |first2=M. |last2=Schlosshauer |title=Niels Bohr as Philosopher of Experiment: Does Decoherence Theory Challenge Bohr's Doctrine of Classical Concepts? |arxiv=1502.06547 |journal=[[Studies in History and Philosophy of Modern Physics]] |volume=49 |pages=73–83 |year=2015 |doi=10.1016/j.shpsb.2015.01.005|bibcode=2015SHPMP..49...73C |s2cid=27697360 }}</ref> Consequently, there is no definitive historical statement of what the interpretation entails. 

Features common across versions of the Copenhagen interpretation include the idea that quantum mechanics is intrinsically [[Indeterminism|indeterministic]], with probabilities calculated using the [[Born rule]], and the principle of [[Complementarity (physics)|complementarity]], which states that objects have certain pairs of complementary properties that cannot all be observed or measured simultaneously.<ref>{{cite book|last=Omnès |first=Roland |author-link=Roland Omnès |chapter=The Copenhagen Interpretation |title=Understanding Quantum Mechanics |publisher=Princeton University Press |year=1999 |pages=41–54 |doi=10.2307/j.ctv173f2pm.9 |s2cid=203390914 |quote=Bohr, Heisenberg, and Pauli recognized its main difficulties and proposed a first essential answer. They often met in Copenhagen ... 'Copenhagen interpretation has not always meant the same thing to different authors. I will reserve it for the doctrine held with minor differences by Bohr, Heisenberg, and Pauli.}}</ref> Moreover, the act of "observing" or "measuring" an object is irreversible, and no truth can be attributed to an object except according to the results of its measurement (that is, the Copenhagen interpretation rejects [[counterfactual definiteness]]). Copenhagen-type interpretations hold that quantum descriptions are objective, in that they are independent of physicists' personal beliefs and other arbitrary mental factors.<ref name="omnes">{{cite book|first=R. |last=Omnès |author-link=Roland Omnès |title=The Interpretation of Quantum Mechanics |publisher=Princeton University Press |year=1994 |isbn=978-0-691-03669-4 |oclc=439453957 }}</ref>{{Rp|85–90}}

Over the years, there have been many objections to aspects of Copenhagen-type interpretations, including the discontinuous and [[stochastic]] nature of the "observation" or "measurement" process, the difficulty of defining what might count as a measuring device, and the seeming reliance upon [[classical physics]] in describing such devices. Still, including all the variations, the interpretation remains one of the most commonly taught.<ref>See, for example:
*{{cite journal |title=How diverse are physics instructors' attitudes and approaches to teaching undergraduate level quantum mechanics?|year=2017|last1=Siddiqui|first1= Shabnam|last2=Singh|first2=Chandralekha|journal=[[European Journal of Physics]] |volume=38 |issue=3 |pages=035703|doi=10.1088/1361-6404/aa6131|bibcode=2017EJPh...38c5703S|doi-access=free}}
*{{cite journal|last=Stapp |first=Henry Pierce |author-link=Henry Stapp |title=The Copenhagen Interpretation |journal=[[Journal of Mind and Behavior|The Journal of Mind and Behavior]] |volume=18 |number=2/3 |publisher=Institute of Mind and Behavior, Inc. |year=1997 |pages=127–54 |jstor=43853817 |quote=led by Bohr and Heisenberg ... was nominally accepted by almost all textbooks and practical workers in the field.}}
*{{cite book|last=Bell |first=John S. |year=1987 |title=Speakable and Unspeakable in quantum Mechanics |location=Cambridge |publisher=Cambridge University Press}}</ref>