#### A. Neumaier

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Reading this paper, I found their reference to a blog article by Reinhard Werner, one of the leaders in quantum information theory, on Bohmian mechanics, with sharp comments and questions such as the following:[49] J. Fröhlich, B. Schubnel: “Quantum Probability Theory and the Foundations of Quantum mechanics”, arXiv:1310.1484v1 [quant-ph].

At the end he poses http://www.itp.uni-hannover.de/~werner/Bohm.html [Broken], for which one can earn a bottle of good wine. I don't know whether @Demystifier likes wine, but perhaps he likes to decide the question with a mathematical proof.Reinhard Werner said:Bohmian trajectories have no connection to empirical fact, and even the Bohmian theory itself claims no connection. So they are just a piece of fantasy. You may call the trajectories the reality givers (I even heard “realizors”) of the theory, and base an “ontology” on them. But they are still but a figment of your imagination. [...]

Why take wave functions as the description of single systems rather than density operators? I could give some arguments for that. You can drive Bohmian trajectories with density operators just as well, and they would tend to be less singular. [...]

Is it really worth saving Physical Reality at the expense of real physics? [...]

To me the “fapp fixed outcomes” problem is a target on which even partial progress is highly welcome. It would require an increase of our understanding of complex systems and an improvement of our mathematical technique. Assuming that to be solved, there would be virtually nothing left of the measurement problem, except maybe a two line historical comment in a paper. The Bohmian perspective seems to be the opposite. You don’t care about the hard problem, but only about that last, utterly trivial bit. [...]

[Bohmian mechanics and quantum mechanics] supposedly make the same predictions about positions, the two are “empirically equivalent”. Note how this argument grants that quantum mechanics had no measurement problem in the first place, since it apparently takes it as unproblematic that there will be agreement. The empirical content of Bohmian Mechanics entirely rests on this bridge. Again, it is left entirely to the quantum physicists to work out how stable pointer positions come about. Bohmian Mechanics will then extend a blessing of Reality. That’s all it does. [...]

If there is no direct connection between observable and Bohmian positions at the microscopic level, how am I justified to assume it at the macroscopic level? Should we invoke prestabilized harmony? Is this not rather like the measurement problem itself? [...]

What kind of physics would Bohm’s Demon see, by which I mean that hypothetical entity with direct access to the Reality of Bohmian trajectories, but to nothing else?

And then follows on the blog a lively debate ....

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