Editing Double-slit experiment (section)

===Interference from individual particles===
An important version of this experiment involves single particle detection. Illuminating the double-slit with a low intensity  results in single particles being detected as white dots on the screen. Remarkably, however, an interference pattern emerges when these particles are allowed to build up one by one (see the image below).
{{multiple image
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| image1            = Roger Bach et al 2013 New J. Phys. 15 033018 Figure 3 cropped to top frame.jpg
| alt1              = Electron diffraction pattern
| image2            = Electron_buildup_movie_from_"Controlled_double-slit_electron_diffraction"_Roger_Bach_et_al_2013_New_J._Phys._15_033018.gif
| alt2              = Dots slowly filling an interference pattern.
| caption2          = Experimental electron double slit diffraction pattern.<ref name="Bach Pope Liou Batelaan 2013 p=033018">{{cite journal | last1=Bach | first1=Roger | last2=Pope | first2=Damian | last3=Liou | first3=Sy-Hwang | last4=Batelaan | first4=Herman | title=Controlled double-slit electron diffraction | journal=New Journal of Physics | publisher=IOP Publishing | volume=15 | issue=3 | date=2013-03-13 | issn=1367-2630 | doi=10.1088/1367-2630/15/3/033018 | page=033018 | arxiv=1210.6243 | bibcode=2013NJPh...15c3018B | s2cid=832961 | url=https://iopscience.iop.org/article/10.1088/1367-2630/15/3/033018}}</ref> Across the middle of the image at the top, the intensity alternates from high to low, showing interference in the signal from the two slits. Bottom: movie of the pattern being built up dot-by-dot. '''Click on the thumbnail to enlarge the movie.'''
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This demonstrates the [[wave–particle duality]], which states that all matter exhibits both wave and particle properties: The particle is measured as a single pulse at a single position, while the modulus squared of the wave describes the [[Probability amplitude|probability]] of detecting the particle at a specific place on the screen giving a statistical interference pattern.<ref>{{cite book |title=The Fabric of the Cosmos: Space, Time, and the Texture of Reality |first1=Brian |last1=Greene |publisher= Random House LLC |year=2007 |isbn=978-0-307-42853-0 |page=90 |url=https://books.google.com/books?id=DNd2K6mxLpIC&pg=PA90}}</ref> This phenomenon has been shown to occur with photons,<ref name="Ananthaswamy">{{cite book
 | last1  = Ananthaswamy
 | first1 = Anil 
 | title  = Through Two Doors at Once: The Elegant Experiment That Captures the Enigma of Our Quantum Reality
 | publisher = Penguin
 | date   = 2018
 | page  = 63
 | isbn   = 978-1-101-98611-0
 }}</ref> electrons,<ref>{{cite journal |last1= Donati |first1= O | last2= Missiroli |first2= G F |last3= Pozzi |first3= G |year= 1973 |title= An Experiment on Electron Interference |journal= American Journal of Physics |volume= 41 |issue = 5| pages = 639–644 |doi= 10.1119/1.1987321 |bibcode= 1973AmJPh..41..639D }}</ref> atoms, and even some molecules: with [[buckminsterfullerene]] ({{chem|C|60}}) in 2001,<ref name="buckyballs" /><ref>[http://www.quantum.at/research/molecule-interferometry-foundations/wave-particle-duality-of-c60.html Wave Particle Duality of C60] {{webarchive |url= https://web.archive.org/web/20120331115055/http://www.quantum.at/research/molecule-interferometry-foundations/wave-particle-duality-of-c60.html |date= 31 March 2012 }}</ref><ref>{{cite journal |last1= Nairz | first1= Olaf |last2= Brezger |first2 = Björn |last3= Arndt |first3= Markus |first4= Anton |last4=Zeilinger |year= 2001 | title= Diffraction of Complex Molecules by Structures Made of Light |journal= Phys. Rev. Lett. |volume = 87 |issue= 16|page= 160401 | doi=10.1103/physrevlett.87.160401|arxiv = quant-ph/0110012 |bibcode = 2001PhRvL..87p0401N | pmid=11690188| s2cid= 21547361 }}</ref><ref>{{cite journal | last1 = Nairz | first1 = O | last2 = Arndt | first2 = M | last3 = Zeilinger | first3 = A | year = 2003 | title = Quantum interference experiments with large molecules | url = https://vcq.quantum.at/fileadmin/Publications/2003-17.pdf | journal = American Journal of Physics | volume = 71 | issue = 4 | pages = 319–325 | doi = 10.1119/1.1531580 | bibcode = 2003AmJPh..71..319N | access-date = 4 June 2015 | archive-url =https://web.archive.org/web/20150604203129/http://vcq.quantum.at/fileadmin/Publications/2003-17.pdf| archive-date = 4 June 2015 }}</ref> with 2 molecules of 430 atoms ({{chem|C|60|(C|12|F|25|)|10}} and {{chem|C|168|H|94|F|152|O|8|N|4|S|4}}) in 2011,<ref>{{cite journal|display-authors=etal |last1=Stefan Gerlich |title=Quantum interference of large organic molecules |journal=Nature Communications |date=5 April 2011 |volume=2 |page=263 |doi=10.1038/ncomms1263 |pmid=21468015 |pmc=3104521 |bibcode=2011NatCo...2..263G }}</ref> and with molecules of up to 2000 atoms in 2019.<ref>{{cite journal |last1=Yaakov Fein |display-authors=etal|title=Quantum superposition of molecules beyond 25kDa |journal=Nature Physics |date=Dec 2019 |volume=15|issue=12|pages=1242–1245|doi=10.1038/s41567-019-0663-9 |bibcode=2019NatPh..15.1242F|s2cid=203638258|url=https://www.nature.com/articles/s41567-019-0663-9.epdf}}</ref>
In addition to interference patterns built up from single particles, up to 4 [[Quantum entanglement|entangled]] photons can also show interference patterns.<ref>Hessmo, B., M. W. Mitchell, and P. Walther. [https://cds.cern.ch/record/1733647/files/vol44-issue6-p011-e.pdf "Entangled photons show interference and bilocation."] CERN Courier (2004): 11.</ref>

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