Of “ an Experimental Test of Non - Local Realism

I make some critical comments on the article [11]. This article makes incorrect claims concerning Bell’s theorem [1]. Moreover, I point to the fact that a hypothesis referred to as “realism” in [11] is not used in the deduction of Leggett’s inequality. “It is the requirement of locality, or more precisely that the result of a measurement on one system be unaffected by operations on a distant system with which it has interacted in the past, that creates the essential difficulty.” John Bell in [1, Introduction]. There is hardly a result that is more widely misunderstood in the scientific community than Bell’s theorem. In a nutshell, there is a widespread belief that in his celebrated article [1], Bell has shown that the assumption of locality, when taken together with an assumption of the existence of hidden variables, allows one to deduce a certain inequality (now known as Bell’s inequality) that contradicts quantum mechanical predictions. A crucial point that is usually overlooked is the fact that the existence of the hidden variables used in the deduction of Bell’s inequality is inferred from the assumption of locality using the EPR argument; it is not, as many physicists seem to think, an additional assumption that is necessary for proving the inequality. Therefore, violation of Bell’s inequality implies that locality has to be abandoned. The misunderstanding regarding the meaning of Bell’s theorem seems to be widespread, but fortunately not universal. Indeed, attempts to clear up the confusion have been made by many authors (see, for instance, [6, pgs. 10—15], [10], [12], [14]), most notably Bell himself. For instance, in footnote number 10 of [3], Bell wrote1: Date: September 7th, 2008. Bell explains his violation of locality argument in several of his writings (see [5] for the collection of Bell’s articles on the Foundations of Quantum Mechanics). In fact, one version of the argument goes directly from locality to an inequality that is violated by the quantum predictions (the Clauser–Holt–Shimony–Horne inequality) and it does not even have to mention any sort of hidden variables (see, for instance, [2] and [3, Section 4]). See also [4] for the (in my opinion) best of Bell’s articles on the subject.