Quantum nonlocality, Bell inequalities, and the memory loophole
Abstract
In the analysis of experiments designed to reveal violation of Belltype inequalities, it is usually assumed that any hidden variables associated with the nth particle pair would be independent of measurement choices and outcomes for the first (n1) pairs. Models which violate this assumption exploit what we call the memory loophole. We focus on the strongest type of violation, which uses the twosided memory loophole, in which the hidden variables for pair n can depend on the previous measurement choices and outcomes in both wings of the experiment. We show that the twosided memory loophole allows a systematic violation of the ClauserHorneShimonyHolt (CHSH) inequality when the data are analyzed in the standard way, but cannot produce a violation if a CHSH expression depending linearly on the data is used. In the first case, the maximal CHSH violation becomes small as the number of particle pairs tested becomes large. Hence, although in principle the memory loophole implies a slight flaw in the existing analyses of Bell experiments, the data still strongly confirm quantum mechanics against local hidden variables. We consider also a related loophole, the simultaneous measurement loophole, which applies if all measurements on each side are carried out simultaneously. We show that this can increase the probability of violating the linearized CHSH inequality as well as other Belltype inequalities.
 Publication:

Physical Review A
 Pub Date:
 October 2002
 DOI:
 10.1103/PhysRevA.66.042111
 arXiv:
 arXiv:quantph/0205016
 Bibcode:
 2002PhRvA..66d2111B
 Keywords:

 03.65.Ud;
 03.65.Ta;
 Entanglement and quantum nonlocality;
 Foundations of quantum mechanics;
 measurement theory;
 Quantum Physics
 EPrint:
 11 pages