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.Physically this meant that one could imagine the electron as a particle alwaysaccompanied by a new kind of wave that gave rise the new "quantum potential" acting onthe particle.He went on to show in his well known 1952 Physical Review papers that youcan explain basic features of non-relativistic quantum theory by assuming that theelectron is such an entity with two aspects: a particle aspect which explains why weobserve a particle-like manifestation every time we observe the electron, and a waveaspect which acts on the particle in a subtle way, thus explaining why the particle aspectobeys the mathematics of wave motion and why electrons collectively produceinterference patterns, without the need to assume the collapse of the wave function.Thetheory was a non-local "hidden variable" theory and was thus a counter-example to vonNeumann's proof that hidden variables are impossible.It met initially with greatresistance but is today, in various developed forms, considered as one of the seriousalternative interpretations of the quantum theory.Everett's interpretationHugh Everett III's interpretation of quantum mechanics (Everett, 1957, 1973), or 'relativestate' theory, despite being the interpretation most often celebrated in fiction, has beenlargely misinterpreted in popular accounts, at least with respect to Everett's originalproposal and this has in part been due to the fact that later adherents imposed their ownreading of the theory.While some of these are worthy of consideration in their own right,much of the criticism directed against Everett's interpretation has in fact objected toaspects that did not appear in the original version.Like Bohm's interpretation, Everett's involves no 'collapse of the wave function'.Butunlike Bohm, Everett accepts the 'reality' of quantum superposition.The heart of Everett'sproposal is in fact that superposition obtains in every case and at every level ofdescription, whether the object of description is the spin state of an electron, the state of apointer in a measuring instrument or even the state of the experimenter's mind looking ata measurement device.Everett proceeds from the observation that collapse is not really a necessary element ofquantum mechanics if there exists a means to establish rigorous correlations betweensuperpositions at various levels.Imagine for instance that an electron, existing in a superposition of 'up' and 'down' spinstates, is 'measured'.For Everett, this means that the superposition of spin states of theelectron leads to a similar superposition in the measuring device, say a superposition ofthe word 'up' being printed and of the word 'down' being printed.The measurementsituation provides an association between the 'up' state appearing in the superposition ofelectron states and the 'up' state appearing in the superposition of measurement devicestates.This can be taken even further so that when the experimenter looks at the printedoutput, her mind also enters a superposition of states involving a state in which she readsthe word 'up' and a state in which she reads the word 'down'.Again there is an associationbetween elements of the superposition at the level of the printout and elements of thesuperposition at the level of the experimenter's mind.From the perspective of any one ofthese superposed minds however, there appears to be no superposition at all.That isbecause the conscious state of the experimenter has become entangled with the state ofthe printout in such a way that the conscious state in which the word 'up' is read is alwaysaccompanied by the state of the measurement device in which the word 'up' is printed.Because the mind is not outside the superposition, but rather itself superposed, theexperimenter exists in one mental state or the other and so sees only the word 'up' or theword 'down' rather than a superposition of both.This has been taken to imply that, since there are now two observers, the universe itselfhas bifurcated, each of the resulting branch universes accommodating only one of theseobservers.The thought behind this is that there is only one 'me' in this universe and anyother versions of 'me', that might perhaps remember different results in a quantummechanics experiment, should go find their own universe.On this reading, every time a'measurement' is made, the universe must similarly 'split' (hence the designation 'many-worlds interpretation').It is this ontologically prodigious contention that has beenrepeatedly criticized as extravagant excess.It gives no account of the process whereby a'split' might occur and one cannot therefore raise the relevant concerns [ Pobierz całość w formacie PDF ]