Einstein's famous critique of quantum mechanics first emerged in 1930, five years earlier than thought, according to a new analysis of his work.
Einstein's phrase "spooky action at a distance" has become synonymous with one of the most famous episodes in the history of physics—his battle with Bohr in the 1930s over the completeness of quantum mechanics.
Einstein's weapons in this battle were thought experiments that he designed to highlight what he believed were the inadequacies of the new theory.
The most famous of these is the EPR paradox, announced in 1935 and named after its inventors Einstein, Boris Podolsky, and Nathan Rosen.
It involves a pair of particles linked by the strange quantum property of entanglement (a word coined much later). Entanglement occurs when two particles are so deeply linked that they share the same existence. In the language of quantum mechanics, they are described by the same mathematical relation known as a wavefunction.
Entanglement arises naturally when two particles are created at the same point and instant in space, for example.
Entangled particles can become widely separated in space. But even so, the mathematics implies that a measurement on one immediately influences the other, regardless of the distance between them.
Einstein and co pointed out that according to special relativity, this was impossible and therefore, quantum mechanics must be wrong, or at least incomplete. Einstein famously called it spooky action at a distance.
The EPR paradox stumped Bohr and was not resolved until 1964, long after Einstein's death. CERN physicist John Bell resolved it by thinking of entanglement as an an entirely new kind of phenomenon, which he termed "nonlocal."
The basic idea here is to think about the transfer of information. Entanglement allows one particle to instantaneously influence another but not in a way that allows classical information to travel faster than light. This resolved the paradox with special relativity but left much of the mystery intact. These days, the curious nature of entanglement is the subject of intense focus in labs around the world.
But that doesn't tell the full story, says Hrvoje Nikoli at the Rudjer Boskovic Institute in Croatia. Today, he reveals that although history first records this paradox in 1935, Einstein unknowingly stumbled across it much earlier, in
1930.
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