Editing Bell test (section)

===Coincidence loophole===
In many experiments, especially those based on photon polarization, pairs of events in the two wings of the experiment are only identified as belonging to a single pair after the experiment is performed, by judging whether or not their detection times are close enough to one another. This generates a new possibility for a local hidden variables theory to "fake" quantum correlations: delay the detection time of each of the two particles by a larger or smaller amount depending on some relationship between hidden variables carried by the particles and the detector settings encountered at the measurement station.<ref name="Larsson2004">{{cite journal |last1=Larsson |first1=Jan-Åke |last2=Gill |first2=Richard |title=Bell's inequality and the coincidence-time loophole |journal=[[Europhysics Letters]] |date=2004 |volume=67 |issue=5 |page=707 |doi=10.1209/epl/i2004-10124-7 |arxiv=quant-ph/0312035|bibcode=2004EL.....67..707L |s2cid=17135877 }}</ref>

The coincidence loophole can be ruled out entirely simply by working with a pre-fixed lattice of detection windows which are short enough that most pairs of events occurring in the same window do originate with the same emission and long enough that a true pair is not separated by a window boundary.<ref name="Larsson2004"/>