Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [184]
'This problem of getting the interpretation proved to be rather more difficult than just working out the equations', said Paul Dirac 50 years after the 1927 Solvay conference.32 The American Nobel laureate Murray Gell-Mann believes part of the reason was that 'Niels Bohr brain-washed a whole generation of physicists into believing that the problem had been solved'.33 A poll conducted in July 1999 during a conference on quantum physics held at Cambridge University revealed the answers of a new generation to the vexed question of interpretation.34 Of the 90 physicists polled, only four voted for the Copenhagen interpretation, but 30 favoured the modern version of Everett's many worlds.35 Significantly, 50 ticked the box labelled 'none of the above or undecided'.
The unresolved conceptual difficulties, such as the measurement problem and the inability to say exactly where the quantum world ends and the classical world of the everyday begins, have led to an increasing number of physicists willing to look for something deeper than quantum mechanics. 'A theory that yields "maybe" as an answer,' says the Dutch Nobel Prize-winning theorist Gerard 't Hooft, 'should be recognized as an inaccurate theory.'36 He believes the universe is deterministic, and is in search of a more fundamental theory that would account for all the strange, counterintuitive features of quantum mechanics. Others like Nicolas Gisin, a leading experimenter exploring entanglement, 'have no problem thinking that quantum theory is incomplete'.37
The emergence of other interpretations and the claim to completeness of quantum mechanics being in serious doubt have led to a reconsideration of the long-standing verdict against Einstein in his long-running debate with Bohr. 'Can it really be true that Einstein, in any significant sense, was as profoundly "wrong" as the followers of Bohr might maintain?' asks the British mathematician and physicist Sir Roger Penrose. 'I do not believe so. I would, myself, side strongly with Einstein in his belief in a submicroscopic reality, and with his conviction that present-day quantum mechanics is fundamentally incomplete.'38
Although he never managed to deliver a decisive blow in his encounters with Bohr, Einstein's challenge was sustained and thought-provoking. It encouraged men like Bohm, Bell and Everett to probe and evaluate Bohr's Copenhagen interpretation when it was all-prevailing and few distinguished theory from interpretation. The Einstein-Bohr debate about the nature of reality was the inspiration behind Bell's theorem. The testing of Bell's inequality directly or indirectly helped spawn new areas of research including quantum cryptography, quantum information theory, and quantum computing. Among the most remarkable of these new fields is quantum teleportation, which exploits the phenomena of entanglement. Although it appears to belong to the realm of science fiction, in 1997 not one but two teams of physicists succeeded in teleporting a particle. The particle was not physically transported, but its quantum state was transferred to a second particle located elsewhere, thereby effectively teleporting the initial particle from one place to another.
After having been marginalised during