Hydrodynamic Quantum Analogs and nonlocality

Last month's SIAM News featured a front-page, above-the-fold article by Prof. John Bush of MIT, "Shifting the Classical-Quantum Boundary:  Insights from Pilot-wave Hydrodynamics".  Among other things, the article challenges the conventional wisdom that quantum theory is inherently and demonstrably nonlocal.  It does so by championing Hydrodynamic Quantum Analogs (HQAs), which are classical analogs of quantum phenomena, using fluid mechanics.  The author uses HQAs to lend credence to the de Broglie-Bohm pilot wave formulation of quantum mechanics.

I have a passing interest in HQAs, regardless of whether they supports alternate interpretations of quantum mechanics, or challenge nonlocality.  I keep an open mind about Bush's assertions, but am neither a cheerleader nor dogmatic opponent of these ideas.  More importantly, I know almost nothing about the field, except what I've learned from Bush's article, and glimpses of other papers in the area (including his) that I've seen over the years.

However I do think Bush does his readers a disservice in the following passage.

The notion of nonlocality, or action at a distance, should be anathema to any rational scientist. Nevertheless, most physicists have made peace with it; they either remain agnostic on the subject or believe it to be an essential, inescapable feature of quantum physics. Because standard quantum theory describes probabilities but not particle dynamics, nonlocality is perceived to be everywhere — in wavefunction collapse, single-particle interference, the quantum mirage, and interaction-free measurement. Correlation at a distance is taken as evidence of action at a distance. HQAs have demonstrated that if we adopt de Broglie’s physical picture of quantum dynamics, we need not invoke nonlocality for any such effects. In short, HQAs suggest that quantum nonlocality is a misinference that is rooted in the incompleteness of quantum theory. While nonlocality is a feature of quantum theory, it need not be a feature of quantum physics.

I've quoted the whole paragraph to ensure that context is provided, but the main problem I have is with the very first sentence of this paragraph.  Should "action at a distance" be "anathema to any rational scientist"?  I am reminded of Bohr's response to Einstein, who said "God does not play dice."  Bohr replied, "Don't tell God what to do."

Newton's original formulation of his gravitational law was manifestly an action-at-a-distance phenomenon.  Yes, it has been superseded by a local field theory, Einstein's general relativity. But is it fair to accuse Newton of not being a "rational scientist"?  (Perhaps so given his interest in alchemy and biblical chronology, but surely not because of his gravity theory!)  What about the 19th century action-at-a-distance rivals to Maxwell's theory (such as Weber's electrodynamics).  Note how Coulomb's law resembles Newton's.  Again, the rival theories were essentially cast aside as incomplete or even wrong once Maxwell's local field theory was fully understood and accepted, but does that make Coulomb, the Webers, and others failures as rational scientists?

Bush gives no citation nor even an argument as to why action at a distance is unworthy of a "rational scientist".  This is because it is nothing more than an opinion, a preference of the author.  He is just offended by the notion of nonlocality in nature.  Offended!

It's okay to be offended.  Such attitudes drive research on the foundations of quantum theory, in defiance of the "shut up and calculate" mentality.  Such research has led to quantum information science, quantum computing, etc.  This is all good stuff!

All I'm saying is that Bush's dictum, that nonlocality should be anathema to rational scientists, is the least persuasive sentence in this article.  The sentence is itself irrational, as it is based on neither reason nor evidence - it is a purely emotional expression as it stands.  And yes I am also making an emotional expression when I condemn it.  

Perhaps there is a good reason that nonlocality should not be considered rational science, and I'm sure other physicists and philosophers have advanced such reasons.  But Bush fails to do so in this article, nor did he cite those who do.  It's nothing but a cheap shot.  In this, he has not served his readers well.

Finally, I realize that it's quite funny that I wrote an entire blog post about one pesky sentence in an otherwise intriguing and informative article :-)