Patrick Alvin M. Alcantara
Einstein maintained that quantum mechanics entails “spooky actions at a distance” (the interaction of two objects which are separated in space with no known mediator of the interaction); experiments have now shown that what bothered Einstein is not a debatable point but the observed behavior of the real world. He called this “spooky action at a distance” because he didn’t know about decoherence, so it seemed spooky to him.
In May 1935, Albert Einstein, Boris Podolsky and Nathan Rosen published the EPR Paper, an argument that quantum mechanics fails to provide a complete description of physical reality. The theoretical and experimental work it inspired remain remarkable for the vivid illustration they provide of one of the most bizarre aspects of the world revealed to us by the quantum theory. Their work describes a situation ingeniously to force the quantum theory into asserting that properties in space-time region B are the result of an act of measurement in another region A; so far from B that there is no possibility of the measurement in A exerting an influence on region B by any known dynamical mechanism. Under these conditions, Einstein maintained that the properties in A must have existed all along. The fundamental result that they were trying to show in their paper was not that quantum mechanics is wrong. They did, in fact, acknowledge that quantum mechanics could be used to make highly accurate statistical predictions about experiments. They were interested mainly in what the fundamental properties of reality are.
Their paper involves a paradox — a thought experiment which challenged long-held ideas about the relation between the observed values of physical quantities and the values that can be accounted for by a physical theory. According to its authors the EPR experiment yields a dichotomy. Either:
- The result of a measurement performed on one part A of a quantum system has a non-local effect on the physical reality of another distant part B, in the sense that quantum mechanics can predict outcomes of some measurements carried out at B.
- Quantum mechanics is incomplete in the sense that some element of physical reality corresponding to B cannot be accounted for by quantum mechanics (that is, some extra variable is needed to account for it).
An enormous set of data, generated out from the apparatus used in the said experiment, by many, many runs. Thus, as Einstein partly said on his letter to Max Born: “…I am therefore inclined to believe that the description of quantum mechanics…has to be regarded as an incomplete and indirect description of reality…”