Interpretation of QM and progress

One of the recorded discussions in Toronto was between Lee Smolin and Martin Roček. They debated the achievements of the research focusing on the interpretational issues of quantum mechanics.

Martin Roček argued that almost no progress occured in this field while Lee Smolin claimed that quantum computing is one of the counterexamples. I tend to agree with Martin.

Quantum mechanics looks weird. As Sidney Coleman once said, if thousands of philosophers were trying to find the weirdest possible thing for thousands of years, they would have never come up with something as strange as quantum mechanics.

But quantum mechanics is true and successfully tested. All those great physicists who could not swallow it and who were proposing various "completions" were wrong. This list includes de Broglie, Schrödinger, Einstein, Podolsky, Rosen, Bohm, Bell, and many others.

We should certainly admit that the questions raised by these Gentlemen were instrumental in deepening our understanding of quantum mechanics. The physicists have understood the EPR effect, entanglement, quantum teleportation, and some mechanisms useful for quantum computing. But it is even more important to say that their opinion that quantum mechanics had to be modified has been falsified as much as you can get.

There have been some unsatisfactory features of the Copenhagen interpretation - such as its unjustified separation of the world into the microscopic and macroscopic realm - but these features do not really affect the predictions for any experiment that has been done (or even realistically planned). Moreover, these features have been more or less clarified by the concept of decoherence from the 1980s that has become a part of satisfactory, modern neo-Copenhagen interpretations of quantum mechanics such as the Consistent Histories.

There also remain several open questions about the interpretation of quantum mechanics in the context of cosmology and quantum gravity (what are the right observables near the Big Bang?), but these questions can hardly be answered before we properly understand dynamics of quantum gravity. Traditionally, dynamics and interpretation are two separated parts of the intellectual structure called quantum theory, and it is only dynamics with which most serious physicists may be spending hundreds of hours and about which they can write quantitative papers. While it is fair to say that quantum gravity has the capacity to smear the boundaries between dynamics and interpretation, it is not fair to say that the people who are simply questioning the foundations of quantum mechanics are contributing to the research of quantum gravity.

Concerning quantum computing, I believe that one of the important boosts for its development came from the 1982 article by Richard Feynman about simulating the quantum world by computers. And Feynman was no philosopher who would like to think about subtle philosophical principles and feel unsatisfied with a working theory of physics because of some abstract prejudices. On the contrary, Feynman thought that the philosophers were politely speaking dopes, and his favorite interpretation of quantum mechanics was summarized by the dictum "Shut up and calculate!".




I personally don't see any significant future for the enterprise of "improving the foundations of quantum mechanics" because the foundations work; all major recipes how to modify them drastically have been shown inconsistent with reality (which showed that the "opponents" of quantum mechanics do not understand an important part of physics well); and new progress in identifying the complete interpretation of quantum mechanics will require more concepts that we will learn from dynamics of quantum gravity.