Editing Bell test (section)

== Notable experiments ==
Over the past half century, a great number of Bell test experiments have been conducted. The experiments are commonly interpreted to rule out local hidden-variable theories, and in 2015 an experiment was performed that is not subject to either the locality loophole or the detection loophole (Hensen et al.<ref name="Hensen et al.">{{cite journal|last1=Hensen|title=Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres|journal=Nature|volume=526|issue=7575|pages=682–686|doi=10.1038/nature15759|display-authors=etal|bibcode = 2015Natur.526..682H|pmid=26503041|year=2015|arxiv=1508.05949|s2cid=205246446 }}</ref>). An experiment free of the locality loophole is one where for each separate measurement and in each wing of the experiment, a new setting is chosen and the measurement completed before signals could communicate the settings from one wing of the experiment to the other. An experiment free of the detection loophole is one where close to 100% of the successful measurement outcomes in one wing of the experiment are paired with a successful measurement in the other wing. This percentage is called the efficiency of the experiment. Advancements in technology have led to a great variety of methods to test Bell-type inequalities.

Some of the best known and recent experiments include:

=== Kasday, Ullman and Wu (1970) ===
[[Leonard Ralph Kasday]], [[Jack R. Ullman]] and [[Chien-Shiung Wu]] carried out the first experimental Bell test, using photon pairs produced by [[positronium]] decay and analyzed by [[Compton scattering]]. The experiment observed photon polarization correlations consistent with quantum predictions and inconsistent with local realistic models that obey the known polarization dependence of Compton scattering. Due to the low polarization selectivity of Compton scattering, the results did not violate a Bell inequality.<ref>{{cite conference |title=Experimental test of quantum predictions for widely separated photons |last1=Kasday |first1=Leonard |author-link1= |last2= |first2= |author-link2= |date=1971 |publisher=Academic Press, New York |book-title= |pages=195–210 |location=Como, Italy |conference=Proceedings of the International School of Physics “Enrico Fermi.” Course 49: Foundations of quantum mechanics |id= |editor = Bernard d'Espagnat |url=https://en.sif.it/books/series/proceedings_fermi}}</ref><ref>{{cite thesis |degree=PhD |last=Kasday |first=Leonard Ralph |date=1972 |title=The distribution of Compton scattered annihilation photons, and the Einstein-Podolsky-Rosen argument |publisher=Columbia University|doi=10.7916/5q2y-3494 |url=https://doi.org/10.7916/5q2y-3494}}</ref>

=== Freedman and Clauser (1972) ===
[[Stuart J. Freedman]] and [[John Clauser]] carried out the first Bell test that observed a Bell inequality violation, using Freedman's inequality, a variant on the [[Clauser and Horne's 1974 Bell test|CH74 inequality]].<ref>{{cite journal |author1=S.J. Freedman |author2=J.F. Clauser |year=1972 |title=Experimental test of local hidden-variable theories |journal=Phys. Rev. Lett. |volume=28 |issue=938 |doi=10.1103/PhysRevLett.28.938 |bibcode=1972PhRvL..28..938F |pages=938–941|url=https://escholarship.org/content/qt2f18n5nk/qt2f18n5nk.pdf?t=p2au19 }}</ref>

=== Aspect et al. (1982) ===
{{main|Aspect's experiment}}
[[Alain Aspect]] and his team at Orsay, Paris, conducted three Bell tests using calcium cascade sources. The first and last used the [[Clauser and Horne's 1974 Bell test|CH74 inequality]]. The second was the first application of the [[CHSH Bell test|CHSH inequality]]. The third (and most famous) was arranged such that the choice between the two settings on each side was made during the flight of the photons (as originally suggested by [[John Stewart Bell|John Bell]]).<ref name="Aspect-1981">{{cite journal |author1=Alain Aspect |author2=Philippe Grangier |author3=Gérard Roger |year=1981 |title=Experimental Tests of Realistic Local Theories via Bell's Theorem |journal=Phys. Rev. Lett. |volume=47 |issue=7 |pages=460–3 |doi=10.1103/PhysRevLett.47.460|bibcode = 1981PhRvL..47..460A|doi-access=free }}</ref><ref name="Aspect-1982b"/>

=== Tittel et al. (1998) ===
The Geneva 1998 Bell test experiments showed that distance did not destroy the "entanglement". Light was sent in fibre optic cables over distances of several kilometers before it was analysed. As with almost all Bell tests since about 1985, a "parametric down-conversion" (PDC) source was used.<ref name="Title-1998a">{{cite journal |author1=W. Tittel |author2=J. Brendel |author3=B. Gisin |author4=T. Herzog |author5=H. Zbinden |author6-link=N. Gisin |author6=N. Gisin |year=1998 |title=Experimental demonstration of quantum-correlations over more than 10 kilometers |journal=Physical Review A |volume=57 |issue=5 |pages=3229–3232 |arxiv=quant-ph/9707042 |doi=10.1103/PhysRevA.57.3229|bibcode = 1998PhRvA..57.3229T|s2cid=55253956 }}</ref><ref name="Title-1998b">{{cite journal |author1=W. Tittel |author2=J. Brendel |author3=H. Zbinden |author4=N. Gisin |year=1998 |title=Violation of Bell inequalities by photons more than 10 km apart |journal=Physical Review Letters |volume=81 |issue=17 |pages=3563–6 |arxiv=quant-ph/9806043 |doi=10.1103/PhysRevLett.81.3563|bibcode = 1998PhRvL..81.3563T|s2cid=55712217 }}</ref>

=== Weihs et al. (1998): experiment under "strict Einstein locality" conditions ===
In 1998 Gregor Weihs and a team at Innsbruck, led by [[Anton Zeilinger]], conducted an experiment that closed the "locality" loophole, improving on Aspect's of 1982. The choice of detector was made using a quantum process to ensure that it was random. This test violated the [[CHSH inequality]] by over 30 standard deviations, the coincidence curves agreeing with those predicted by quantum theory.<ref name="Weihs-1998"/>

=== Pan et al. (2000) experiment on the GHZ state ===
This is the first of new Bell-type experiments on more than two particles; this one uses the so-called [[Greenberger-Horne-Zeilinger state|GHZ state]] of three particles.<ref name="GHZ2000">{{cite journal |author1=Jian-Wei Pan |author2=D. Bouwmeester |author3=M. Daniell |author4=H. Weinfurter |author5=A. Zeilinger |year=2000 |title=Experimental test of quantum nonlocality in three-photon GHZ entanglement |journal=Nature |volume=403 |issue=6769 |pages=515–519 |bibcode=2000Natur.403..515P |doi=10.1038/35000514 |pmid=10676953|s2cid=4309261 }}</ref>

=== Rowe et al. (2001): the first to close the detection loophole ===
The detection loophole was first closed in an experiment with two entangled trapped ions, carried out in the ion storage group of David Wineland at the National Institute of Standards and Technology in Boulder. The experiment had detection efficiencies well over 90%.<ref>{{cite journal |author1=M.A. Rowe |author2=D. Kielpinski |author3=V. Meyer |author4=C.A. Sackett |author5=W.M. Itano |author6=C. Monroe |author7=D.J. Wineland |year=2001 |title=Experimental violation of a Bell's inequality with efficient detection |journal=Nature |volume=409 |issue=6822 |pages=791–94 |doi=10.1038/35057215|bibcode = 2001Natur.409..791R |pmid=11236986|url=https://deepblue.lib.umich.edu/bitstream/2027.42/62731/1/409791a0.pdf |hdl=2027.42/62731 |s2cid=205014115 |hdl-access=free }}</ref>

=== Go et al. (Belle collaboration): Observation of Bell inequality violation in B mesons ===
Using semileptonic B0 decays of Υ(4S) at Belle experiment, a clear violation of Bell Inequality in particle-antiparticle correlation is observed.<ref>{{cite journal | title=Observation of Bell Inequality violation in B mesons| year=2004| doi=10.1080/09500340408233614| arxiv=quant-ph/0310192| last1=Go| first1=Apollo| journal=Journal of Modern Optics| volume=51| issue=6–7| pages=991–998| bibcode=2004JMOp...51..991G| s2cid=15807552}}</ref>

=== Gröblacher et al. (2007) test of Leggett-type non-local realist theories ===
A specific class of non-local theories suggested by [[Anthony Leggett]] is ruled out. Based on this, the authors conclude that any possible [[quantum nonlocality|non-local]] [[hidden-variable theory]] consistent with quantum mechanics must be highly counterintuitive.<ref name="quantum">{{cite web |year=2007 |title=Quantum physics says goodbye to reality |publisher=physicsworld.com |url=https://physicsworld.com/cws/article/news/27640 |archive-url=https://web.archive.org/web/20071019231848/https://physicsworld.com/cws/article/news/27640 |url-status=dead |archive-date=2007-10-19 }}</ref><ref name="quantum2">{{cite journal |author1=S Gröblacher |author2=T Paterek |author3=Rainer Kaltenbaek |author4=S Brukner |author5=M Zukowski |author6=M Aspelmeyer |author7=A Zeilinger |year=2007 |title=An experimental test of non-local realism |journal=Nature |volume=446 |issue=7138 |pages=871–5 |doi=10.1038/nature05677|arxiv = 0704.2529 |bibcode = 2007Natur.446..871G |pmid=17443179|s2cid=4412358 }}</ref>

=== Salart et al. (2008): separation in a Bell Test ===
This experiment filled a loophole by providing an 18&nbsp;km separation between detectors, which is sufficient to allow the completion of the quantum state measurements before any information could have traveled between the two detectors.<ref>{{cite journal |author=Salart, D. |author2=Baas, A. |author3=van Houwelingen, J. A. W. |author4=Gisin, N. |author5=Zbinden, H. |name-list-style=amp |year=2008 |title=Spacelike Separation in a Bell Test Assuming Gravitationally Induced Collapses |journal=Physical Review Letters |volume=100 |issue=22 |page=220404 |arxiv=0803.2425 |doi=10.1103/PhysRevLett.100.220404|bibcode = 2008PhRvL.100v0404S |pmid=18643408|s2cid=22151690 }}</ref><ref>{{cite web |title=World's Largest Quantum Bell Test Spans Three Swiss Towns |publisher=phys.org |date=2008-06-16 |url=http://www.physorg.com/news132830327.html}}</ref>

=== Ansmann et al. (2009): overcoming the detection loophole in solid state ===
This was the first experiment testing Bell inequalities with solid-state qubits (superconducting [[Phase qubit|Josephson phase qubits]] were used). This experiment surmounted the detection loophole using a pair of superconducting qubits in an entangled state. However, the experiment still suffered from the locality loophole because the qubits were only separated by a few millimeters.<ref>{{cite journal |last=Ansmann |first=Markus |author2=H. Wang |author3=Radoslaw C. Bialczak |author4=Max Hofheinz |author5=Erik Lucero |author6=M. Neeley |author7=A. D. O'Connell |author8=D. Sank |author9=M. Weides |author10=J. Wenner |author11=A. N. Cleland |author12=John M. Martinis |date=2009-09-24 |title=Violation of Bell's inequality in Josephson phase qubits |journal=Nature |volume=461 |issue=504–6 |pages=504–6 |doi=10.1038/nature08363 |bibcode=2009Natur.461..504A |pmid=19779447|s2cid=4401494 }}</ref>

=== [[Marissa Giustina|Giustina]] et al. (2013), Larsson et al (2014): overcoming the detection loophole for photons ===
The detection loophole for photons has been closed for the first time by [[Marissa Giustina]], using [[Transition edge sensor|highly efficient detectors]]. This makes photons the first system for which all of the main loopholes have been closed, albeit in different experiments.<ref name="giustina">{{cite journal|last=Giustina|first=Marissa|author2=Alexandra Mech|author3=Sven Ramelow|author4=Bernhard Wittmann|author5=Johannes Kofler|author6=Jörn Beyer|author7=Adriana Lita|author-link7=Adriana Lita|author8=Brice Calkins|author9=Thomas Gerrits|author10=Sae Woo Nam|author11=Rupert Ursin|date=2013-04-14|title=Bell violation using entangled photons without the fair-sampling assumption|journal=Nature|volume=497|issue=7448|pages=227–30|arxiv=1212.0533|bibcode=2013Natur.497..227G|doi=10.1038/nature12012|pmid=23584590|author12=Anton Zeilinger|s2cid=18877065 }}</ref><ref name = "larsson"/>

=== Christensen et al. (2013): overcoming the detection loophole for photons ===
The Christensen et al. (2013)<ref name = "christensen">{{cite journal |last=Christensen |first=B.G. |author2=K. T. McCusker |author3=J. Altepeter |author4=B. Calkins |author5=T. Gerrits |author6=A. Lita |author7=A. Miller |author8=L. K. Shalm |author9=Y. Zhang |author10=S. W. Nam |author11=N. Brunner |author12=C. C. W. Lim | author13 = N. Gisin |author14-link=Paul Kwiat| author14 = P. G. Kwiat | date= 26 September 2013|title=Detection-Loophole-Free Test of Quantum Nonlocality, and Applications |journal=Physical Review Letters |volume=111 |issue=7448 |pages=130406 |doi=10.1103/PhysRevLett.111.130406 |arxiv= 1306.5772 |bibcode = 2013PhRvL.111m0406C | pmid=24116754|s2cid=14278916 }}</ref> experiment is similar to that of Giustina et al.<ref name="giustina" /> Giustina et al. did just four long runs with constant measurement settings (one for each of the four pairs of settings). The experiment was not pulsed so that formation of "pairs" from the two records of measurement results (Alice and Bob) had to be done after the experiment which in fact exposes the experiment to the coincidence loophole. This led to a reanalysis of the experimental data in a way which removed the coincidence loophole, and fortunately the new analysis still showed a violation of the appropriate CHSH or CH inequality.<ref name="larsson">{{cite journal |last=Larsson |first= Jan-Åke |author2=Marissa Giustina |author3= Johannes Kofler |author4=Bernhard Wittmann |author5=Rupert Ursin |author6=Sven Ramelow |date=16 September 2014 |title=Bell violation with entangled photons, free of the coincidence-time loophole |journal=Physical Review A |volume=90 |issue=7448 |pages=032107 |doi=10.1103/PhysRevA.90.032107 |arxiv=1309.0712 |bibcode=2014PhRvA..90c2107L|s2cid= 40197990 }}</ref> On the other hand, the Christensen et al. experiment was pulsed and measurement settings were frequently reset in a random way, though only once every 1000 particle pairs, not every time.<ref name="christensen" />

=== Hensen et al., Giustina et al., Shalm et al. (2015): "loophole-free" Bell tests ===
<!-- Note: The first author in the Ronald Hanson group is "B. Hensen" -->
In 2015 the first three significant-loophole-free Bell-tests were published within three months<!-- Timespan: 78 days--> by independent groups in Delft, Vienna and Boulder. All three tests simultaneously addressed the detection loophole, the locality loophole, and the memory loophole. This makes them “loophole-free” in the sense that all remaining conceivable loopholes like [[superdeterminism]] require truly exotic hypotheses that might never get closed experimentally.

The first published experiment by Hensen et al.<ref name="Hensen et al." /> used a photonic link to entangle the [[Electron magnetic moment|electron spins]] of two [[Nitrogen-vacancy center|nitrogen-vacancy]] defect centres in diamonds 1.3 kilometers apart and measured a violation of the CHSH inequality (''S'' = 2.42 ± 0.20). Thereby the local-realist hypothesis could be rejected with a [[p-value|''p''-value]] of 0.039.

Both simultaneously published experiments by Giustina et al.<ref name="Zeilinger-2015">{{Cite journal|last1=Giustina |first1=Marissa |last2=Versteegh |first2=Marijn A. M. |last3=Wengerowsky |first3=Soeren |last4=Handsteiner |first4=Johannes |last5=Hochrainer |first5=Armin |last6=Phelan |first6=Kevin |last7=Steinlechner |first7=Fabian |last8=Kofler |first8=Johannes |last9=Larsson |first9=Jan-Ake |last10=Abellan |first10=Carlos |last11=Amaya |first11=Waldimar |last12=Pruneri |first12=Valerio |last13=Mitchell |first13=Morgan W. |last14=Beyer |first14=Joern |last15=Gerrits |first15=Thomas |last16=Lita |first16=Adriana E. |last17=Shalm |first17=Lynden K. |last18=Nam |first18=Sae Woo |last19=Scheidl |first19=Thomas |last20=Ursin |first20=Rupert |last21=Wittmann |first21=Bernhard |last22=Zeilinger |first22=Anton |arxiv=1511.03190 |title=A significant-loophole-free test of Bell's theorem with entangled photons |journal=Physical Review Letters |volume=115 |issue=25 |pages=250401 |date=2015|doi=10.1103/PhysRevLett.115.250401 |pmid=26722905 |bibcode=2015PhRvL.115y0401G |s2cid=13789503 }}</ref>
and Shalm et al.<ref name="Kwiat-2015">{{cite journal |first1=Lynden K.|last1=Shalm |first2=Evan|last2=Meyer-Scott |first3=Bradley G.|last3=Christensen |first4=Peter|last4=Bierhorst |first5=Michael A.|last5=Wayne |first6=Martin J.|last6=Stevens |first7=Thomas|last7=Gerrits |first8=Scott|last8=Glancy |first9=Deny R.|last9=Hamel |first10=Michael S.|last10=Allman |first11=Kevin J.|last11=Coakley |first12=Shellee D.|last12=Dyer |first13=Carson|last13=Hodge |first14=Adriana E.|last14=Lita |first15=Varun B.|last15=Verma |first16=Camilla|last16=Lambrocco |first17=Edward|last17=Tortorici |first18=Alan L.|last18=Migdall |first19=Yanbao|last19=Zhang |first20=Daniel R.|last20=Kumor |first21=William H.|last21=Farr |first22=Francesco|last22=Marsili |first23=Matthew D.|last23=Shaw |first24=Jeffrey A.|last24=Stern |first25=Carlos|last25=Abellán |first26=Waldimar|last26=Amaya |first27=Valerio|last27=Pruneri |first28=Thomas|last28=Jennewein |first29=Morgan W.|last29=Mitchell |first30=Paul G.|last30=Kwiat |first31=Joshua C.|last31=Bienfang |first32=Richard P.|last32=Mirin |first33=Emanuel|last33=Knill |first34=Sae Woo|last34=Nam |arxiv=1511.03189 |title=A strong loophole-free test of local realism |date=2015 |doi=10.1103/PhysRevLett.115.250402 |pmid=26722906 |pmc=5815856 |volume=115 |issue=25 |journal=Phys Rev Lett |page=250402|bibcode = 2015PhRvL.115y0402S |display-authors=29 }}</ref>
used entangled photons to obtain a Bell inequality violation with high statistical significance (p-value ≪10<sup>−6</sup>). Notably, the experiment by Shalm et al. also combined three types of (quasi-)random number generators to determine the measurement basis choices. One of these methods, detailed in an ancillary file, is the “'Cultural' [[Pseudorandom number generator|pseudorandom]] source” which involved using bit strings from popular media such as the [[Back to the Future (franchise)|''Back to the Future'' films]], ''[[Star Trek: Beyond the Final Frontier]]'', ''[[Monty Python and the Holy Grail]]'', and the television shows ''[[Saved by the Bell]]'' and ''[[Doctor Who|Dr. Who]]''.<ref>{{Cite journal|arxiv=1511.03189|last1=Shalm|first1=Lynden K|title=A strong loophole-free test of local realism|journal=Physical Review Letters|volume=115|issue=25|pages=250402|last2=Meyer-Scott|first2=Evan|last3=Christensen|first3=Bradley G|last4=Bierhorst|first4=Peter|last5=Wayne|first5=Michael A|last6=Stevens|first6=Martin J|last7=Gerrits|first7=Thomas|last8=Glancy|first8=Scott|last9=Hamel|first9=Deny R|last10=Allman|first10=Michael S|last11=Coakley|first11=Kevin J|last12=Dyer|first12=Shellee D|last13=Hodge|first13=Carson|last14=Lita|first14=Adriana E|last15=Verma|first15=Varun B|last16=Lambrocco|first16=Camilla|last17=Tortorici|first17=Edward|last18=Migdall|first18=Alan L|last19=Zhang|first19=Yanbao|last20=Kumor|first20=Daniel R|last21=Farr|first21=William H|last22=Marsili|first22=Francesco|last23=Shaw|first23=Matthew D|last24=Stern|first24=Jeffrey A|last25=Abellán|first25=Carlos|last26=Amaya|first26=Waldimar|last27=Pruneri|first27=Valerio|last28=Jennewein|first28=Thomas|last29=Mitchell|first29=Morgan W|last30=Kwiat|first30=Paul G|display-authors=29|year=2015|doi=10.1103/PhysRevLett.115.250402|pmid=26722906|pmc=5815856|bibcode=2015PhRvL.115y0402S}}</ref>

=== Schmied et al. (2016): Detection of Bell correlations in a many-body system ===
Using a witness for Bell correlations derived from a multi-partite Bell inequality, physicists at the [[University of Basel]] were able to conclude for the first time Bell correlation in a many-body system composed by about 480 atoms in a [[Bose–Einstein condensate]]. Even though loopholes were not closed, this experiment shows the possibility of observing Bell correlations in the macroscopic regime.<ref>{{cite journal | last1 = Schmied | first1 = R. | last2 = Bancal | first2 = J.-D. | last3 = Allard | first3 = B. | last4 = Fadel | first4 = M. | last5 = Scarani | first5 = V. | last6 = Treutlein | first6 = P. | last7 = Sangouard | first7 = N. | year = 2016 | title = Bell correlations in a Bose–Einstein condensate | journal = Science | volume = 352 | issue = 6284 | pages = 441–4 | doi = 10.1126/science.aad8665 | pmid = 27102479 |arxiv = 1604.06419 | bibcode = 2016Sci...352..441S | s2cid = 206645325 }}</ref>

=== Handsteiner et al. (2017): "Cosmic Bell Test" - Measurement Settings from Milky Way Stars ===
Physicists led by [[David Kaiser (physicist)|David Kaiser]] of the [[Massachusetts Institute of Technology]] and Anton Zeilinger of the [[Institute for Quantum Optics and Quantum Information]] and [[University of Vienna]] performed an experiment that "produced results consistent with nonlocality" by measuring starlight that had taken 600 years to travel to Earth.<ref>{{Cite journal|title=Synopsis: Cosmic Test of Quantum Mechanics |journal=Physical Review Letters |volume=118 |issue=6 |pages = 060401|date=2017-02-07 |doi=10.1103/PhysRevLett.118.060401 |pmid=28234500 |last1=Handsteiner |first1=Johannes |last2=Friedman |first2=Andrew S |last3=Rauch |first3=Dominik |last4=Gallicchio |first4=Jason |last5=Liu |first5=Bo |last6=Hosp |first6=Hannes |last7=Kofler |first7=Johannes |last8=Bricher |first8=David |last9=Fink |first9=Matthias |last10=Leung |first10=Calvin |last11=Mark |first11=Anthony |last12=Nguyen |first12=Hien T |last13=Sanders |first13=Isabella |last14=Steinlechner |first14=Fabian |last15=Ursin |first15=Rupert |last16=Wengerowsky |first16=Sören |last17=Guth |first17=Alan H |last18=Kaiser |first18=David I |last19=Scheidl |first19=Thomas |last20=Zeilinger |first20=Anton |arxiv=1611.06985 |bibcode=2017PhRvL.118f0401H |s2cid=4607466 }}</ref> The experiment “represents the first experiment to dramatically limit the space-time region in which hidden variables could be relevant.”<ref>{{Cite journal|last=Handsteiner|first=Johannes|date=2017-01-01|title=Cosmic Bell Test: Measurement Settings from Milky Way Stars|journal=Physical Review Letters|volume=118|issue=6|pages=060401|doi=10.1103/PhysRevLett.118.060401|pmid=28234500|bibcode=2017PhRvL.118f0401H|arxiv = 1611.06985 |s2cid=4607466 }}</ref><ref>{{Cite web|url=https://www.quantamagazine.org/20170207-bell-test-quantum-loophole/|title=Experiment Reaffirms Quantum Weirdness |work=[[Quanta Magazine]] |last=Wolchover|first=Natalie |author-link=Natalie Wolchover |language=en-US |access-date=2020-02-08 |date=2017-02-07}}</ref><ref>{{Cite journal|title=Cosmic experiment is closing another Bell test loophole |language=en|doi=10.1063/pt.5.2051|journal=Physics Today|year=2016}}</ref>

=== Rosenfeld et al. (2017): "Event-Ready" Bell test with entangled atoms and closed detection and locality loopholes ===
Physicists at the [[Ludwig Maximilian University of Munich]] and the [[Max Planck Institute of Quantum Optics]] published results from an experiment in which they observed a Bell inequality violation using entangled spin states of two atoms with a separation distance of 398 meters in which the detection loophole, the locality loophole, and the memory loophole were closed. The violation of S = 2.221 ± 0.033 rejected local realism with a significance value of P = 1.02×10<sup>−16</sup> when taking into account 7 months of data and 55000 events or an upper bound of P = 2.57×10<sup>−9</sup> from a single run with 10000 events.<ref>{{cite journal | last1 = Rosenfeld | first1 = W. | last2 = Burchardt | first2 = D. | last3 = Garthoff | first3 = R. | last4 = Redeker | first4 = K. | last5 = Ortegel | first5 = N. | last6 = Rau | first6 = M. | last7 = Weinfurter | first7 = H. | year = 2017 | title = Event-Ready Bell Test Using Entangled Atoms Simultaneously Closing Detection and Locality Loopholes | journal = Physical Review Letters | volume = 119 | issue = 1| page = 010402 | doi = 10.1103/PhysRevLett.119.010402 | pmid = 28731745 | bibcode=2017PhRvL.119a0402R|arxiv = 1611.04604 | s2cid = 10424009 }}</ref>

=== The BIG Bell Test Collaboration (2018): “Challenging local realism with human choices” ===
An international collaborative scientific effort used arbitrary human choice to define measurement settings instead of using random number generators. Assuming that human free will exists, this would close the “freedom-of-choice loophole”. Around 100,000 participants were recruited in order to provide sufficient input for the experiment to be statistically significant.<ref>{{Cite journal|date=May 2018|title=Challenging local realism with human choices|journal=Nature|volume=557|issue=7704|pages=212–216|doi=10.1038/s41586-018-0085-3|pmid=29743691|issn=0028-0836|bibcode=2018Natur.557..212B|author1=BIG Bell Test Collaboration|arxiv=1805.04431|s2cid=186245057 }}</ref>

=== Rauch et al (2018): measurement settings from distant quasars ===
In 2018, an international team used light from two [[quasar]]s (one whose light was generated approximately eight billion years ago and the other approximately twelve billion years ago) as the basis for their measurement settings.<ref name="Hamish 2018">{{cite news |last1=Johnston |first1=Hamish |title=Cosmic Bell test uses light from ancient quasars |url=https://physicsworld.com/a/cosmic-bell-test-uses-light-from-ancient-quasars/ |access-date=10 January 2021 |publisher=[[Physics World]] |date=21 Aug 2018}}</ref>  This experiment pushed the timeframe for when the settings could have been mutually determined to at least 7.8 billion years in the past, a substantial fraction of the [[superdeterminism|superdeterministic]] limit (that being the [[Big Bang|creation of the universe]] 13.8 billion years ago).<ref>{{Cite journal|title=Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars|date=Aug 20, 2018|journal=Physical Review Letters|volume=121|issue=8|pages=080403|doi=10.1103/PhysRevLett.121.080403|pmid=30192604|last1 = Rauch|first1 = Dominik|last2=Handsteiner|first2=Johannes|last3=Hochrainer|first3=Armin|last4=Gallicchio|first4=Jason|last5=Friedman|first5=Andrew S.|last6=Leung|first6=Calvin|last7=Liu|first7=Bo|last8=Bulla|first8=Lukas|last9=Ecker|first9=Sebastian|last10=Steinlechner|first10=Fabian|last11=Ursin|first11=Rupert|last12=Hu|first12=Beili|last13=Leon|first13=David|last14=Benn|first14=Chris|last15=Ghedina|first15=Adriano|last16=Cecconi|first16=Massimo|last17=Guth|first17=Alan H.|last18=Kaiser|first18=David I.|last19=Scheidl|first19=Thomas|last20=Zeilinger|first20=Anton|arxiv=1808.05966|bibcode=2018PhRvL.121h0403R |s2cid=52059624 }}</ref>

The 2019 [[PBS Nova]] episode ''Einstein's Quantum Riddle'' documents this "cosmic Bell test" measurement, with footage of the scientific team on-site at the high-altitude [[Teide Observatory]] located in the [[Canary Islands]].<ref>{{cite web |title=Einstein's Quantum Riddle |url=https://www.pbs.org/wgbh/nova/video/einsteins-quantum-riddle/ |publisher=[[PBS Nova]] |access-date=23 December 2020 |date=9 Jan 2019}}</ref>

=== Storz et al (2023): Loophole-free Bell inequality violation with superconducting circuits ===
In 2023, an international team led by the group of [[Andreas Wallraff]] at [[ETH Zurich]] demonstrated a loophole-free violation of the [[CHSH inequality]] with superconducting circuits deterministically entangled via a cryogenic link spanning a distance of 30 meters.<ref>{{cite journal |last1=Storz |first1=Simon |last2=Schär |first2=Joshua |last3=Kulikov |first3=Anatoly |last4=Magnard |first4=Paul |last5=Kurpiers |first5=Philipp |last6=Lütolf |first6=Janice |last7=Walter |first7=Theo |last8=Copetudo |first8=Adrian |last9=Reuer |first9=Kevin |last10=Akin |first10=Abdulkadir |last11=Besse |first11=Jean-Claude |last12=Gabureac |first12=Mihai |last13=Norris |first13=Graham J. |last14=Rosario |first14=Andrés |last15=Martin |first15=Ferran |last16=Martinez |first16=José |last17=Amaya |first17=Waldimar |last18=Mitchell |first18=Morgan W. |last19=Abellan |first19=Carlos |last20=Bancal |first20=Jean-Daniel |last21=Sangouard |first21=Nicolas |last22=Royer |first22=Baptiste |last23=Blais |first23=Alexandre |last24=Wallraff |first24=Andreas |date=2023 |title=Loophole-free Bell inequality violation with superconducting circuits  |journal=Nature |volume=617 |issue= 7960|pages=265–270 |doi=10.1038/s41586-023-05885-0 |pmid=37165240 |bibcode=2023Natur.617..265S |doi-access=free |hdl=20.500.11850/612915 |hdl-access=free }}</ref>