Reply To: Comments on Bohmian mechanics

Aurelien Drezet

Dear Richard, I would like to comment briefly on your suggestion that the so called orthodox interpretation of QM (OIQM) is better than the de Broglie Bohm approach.
I think that the crucial element which is missing in the OIQM is a clear statement of what is ontology in QM. For Bohr the world must be described by something classical but he is not really able to say what does it really mean. The apparatus is at the end a quantum object and the point of Heisenberg and Bohr is that we must introduce a kind of cut or shifty split. Where does the split occurs this is the big issue in the OIQM and Heisenberg only pointed out that the position of the split is irrelevant. Of course, he was right in the sense that is now given by decoherence theory à la Zurek but still the ontology is not better that it was at the time of Bohr since the environment should be included as an observer in the interpretation. This is even more mysterious since the exact nature of the environment is illusive and also shifty. Do we need to say that the” Universe “ is an observer? For me the OIQM is paradoxical with or without decoherence. Consider the Schrodinger cat or the Wigner friend paradox ; these are examples showing that the border between what is described by the wave function and by the observer has an impact on the ontological nature of the object. The quantum system can’ t at the same time be and not here.! But remember: Following the OIQM the exact nature of an electron before a measurement by an observer is undefined. This is necessary for Bohr otherwise the electron could follow two paths at the same time (I.e. wave particle duality). So if this true for an electron is must also be true for an observer watching a second observer. I can not see how you can exit this circle in the context of OIQM (this was the point of Everett in his thesis). For me the role of the observer is too fragile its definition too mysterious to give a good basis for an interpretation of QM. We need something better something of clear and I think we should accept a realistic view to solve the measurement problem. Bohmian mechanics is the first step. It shows that this is possible. I do not think that the theory will survive in its current form but I believe that OIQM is a dead end for making progress in physics.

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