Nicolas Gisin is an experimental physicist who has extended the tests of quantum entanglement and nonlocality (the EPR experiment) to many kilometers from his lab in Geneva. His work has confirmed the correctness of quantum mechanics, and with it the irreducible indeterminacy involved in quantum mechanical measurements. Gisin is the recipient of the first John Stewart Bell prize. It is Bell's Theorem and the Bell Inequalities that Gisin's work has confirmed. Despite his critical work that grounds quantum physics, Gisin has been active in searching for alternative mathematical formulations of quantum theory, especially ones that might replace the ad hoc assumption of wave functions "collapsing" when measurements are made. Alternatives proposed by GianCarlo Ghirardi and his colleagues replace the linear Schrödinger equation for the time evolution of the wave function with a nonlinear equation that includes explicit stochastic terms. Gisin also has explored the paradoxical interpretations of his nonlocality experiments. The perfect nonlocal correlation of distant spin states suggests that information is traveling between the two widely separated measurements of electrons in an entangled spin state at velocities greater than the speed of light. This is of course impossible, but Gisin speculates that some "influence" may be affecting both experiments coming from "outside space and time." Gisin says he means by this that "there is no story in space and time" to account for nonlocality. This is of course because the collapse of probabilities is instantaneous (not therefore "in time?") and happens everywhere (surely "in all space?"). If there were such influences, they might provide an explanation for deterministic theories, "some sort of hyper-determinism that would make all Science an illusion," says Gisin. He explains:
We have seen that any proper violation of a Bell inequality implies that all possible future theories have to predict nonlocal correlations. In this sense it is Nature that is nonlocal. But how can that be? How does Nature perform the trick? Leaving aside some technical loopholes, like a combination of detection and locality loopholes, the obvious answer, already suggested by John Bell, is that there is some hidden communication going on behind the scene. A first meaning of "behind the scene" could be "beyond today's physics", in particular beyond the speed limit set by relativity. We have seen how this interesting idea can be experimentally tested and how difficult it is to combine this idea with no-signaling. Hence, it is time to take seriously the idea that Nature is able to produce nonlocal correlations. There are several ways of formulating this: 1. Somehow God plays dice with nonlocal die: a random event can manifest itself at several locations. 2. Nonlocal correlations merely happen. somehow from outside space-time, in the sense that no story in space-time can describe how they happen. 3. The communications behind the scene happens outside space-time 4. Reality happens in configuration space: what we observe is only a shadow in 3-dimensional space (this might be closest to the description provided by standard quantum physics).
Free willGisin says about free will,
Descartes pineal gland. In standard quantum physics such an interface between free will and physics could be even simpler: free will could influence the probabilities of quantum events. This is, admittedly, a vague and not very original idea; but important is that there is no obvious definite contradiction between free will and standard quantum physics.I know that I enjoy free will much more than I know anything about physics. Hence, physics will never be able to convince me that free will is an illusion. Quite the contrary, any physical hypothesis incompatible with free will is falsified by the most profound experience I have about free will. So, would I have rejected Newtonian classical mechanics had I lived before quantum physics? Probably not. Indeed, classical physics leaves open the possibility that free will can somehow interface with the deterministic Newtonian equations: free will could set-up some potential that could slightly influence particles's motion. This would be something like
For ScholarsThe experimental setup for quantum entanglement tests is theoretically simple but experimentally difficult. Two spin 1/2 electrons are prepared in a state, say with opposing spins so the total spin angular momentum of the electrons is zero. They are said to be in a singlet state. Most recent studies, like Gisin's, used entangled polarized photon pairs.) Two experimenters (call them A and B) measure the electron spins at some later time. The conservation of angular momentum requires that should one of these electrons be measured with spin up, the other must be spin down. This is what is described as "nonlocal" correlation of the spin measurement results. A simpler way of looking at the problem is to consider the conservation of angular momentum, a law of nature that can not be violated. What would the lack of "correlation" between electron spins look like? It would include some spin-up measurements by experimenter A at the same time as spin-up measurements by experimenter B. But this is a clear violation of the conservation law for angular momentum. This conservation law in no way depends on supra-luminal communications between particles. Consider two electrons at opposite ends of the Andromeda galaxy, say 100,000 light years apart. As they revolve around the center of the galaxy, they conserve their orbital angular momenta perfectly. We might say that conservation laws are "outside space-time." Note that the original EPR thought experiment involved electrons going in opposite directions from a central source. In that case the governing conservation law was for ordinary translational momentum.
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