Loopholes in Bell inequality tests of local realism Jan-Åke Larsson Linköping University Post Print N.B.: When citing this work, cite the original article. Original Publication: Jan-Åke Larsson, Loopholes in Bell inequality tests of local realism, 2014, Journal of Physics A: Mathematical and Theoretical, (47), 42, 424003. http://dx.doi.org/10.1088/1751-8113/47/42/424003 Copyright: IOP Publishing: Hybrid Open Access http://www.iop.org/ Postprint available at: Linköping University Electronic Press http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112644 Loopholes in Bell Inequality Tests of Local Realism Jan-Ake˚ Larsson Institutionen f¨orsystemteknik, Link¨opingsUniversitet, 581 83 Link¨oping,Sweden E-mail:
[email protected] Abstract. Bell inequalities are intended to show that local realist theories cannot describe the world. A local realist theory is one where physical properties are defined prior to and independent of measurement, and no physical influence can propagate faster than the speed of light. Quantum-mechanical predictions for certain experiments violate the Bell inequality while a local realist theory cannot, and this shows that a local realist theory cannot give those quantum-mechanical predictions. However, because of unexpected circumstances or \loopholes" in available experiment tests, local realist theories can reproduce the data from these experiments. This paper reviews such loopholes, what effect they have on Bell inequality tests, and how to avoid them in experiment. Avoiding all these simultaneously in one experiment, usually called a \loophole-free" or “definitive" Bell test, remains an open task, but is very important for technological tasks such as device-independent security of quantum cryptography, and ultimately for our understanding of the world.