On the foundations of quantum mechanics

One of the most fascinating and to my mind central questions of contemporary physics is the ontological status of quantum objects – does the quantum wavefunction describe reality as it is, or merely our possible knowledge of it. A related question is: where is the limit between the quantum and the classical? Earlier assumptions about limiting quantum effects to extremely small systems (see also a TED talk on the topic), only non-biological systems, or extremely cold systems have all been vigorously pushed back by improvements in experimental techniques. As a primer on the subject, the Brooklyn Institute for Social Research published an interesting discussion with philosopher David Albert on the foundations of quantum physics. Albert is – somewhat controversially – extremely ambitious for the ultimate scope of physical theory, which in his view should incorporate our consciousness and psychology as well. However, he interestingly does NOT consider the question "why is there something rather than nothing", which was touched on in the previous post, to be a valid scientific question. In any case, it's a fascinating and accessible talk and the first part about the foundations of quantum mechanics and the measurement problem is particularly good.

Update (12.9.2012): a new news article was just posted on Nature News on the limitations of Heisenberg's original formulation of the uncertainty principle, which is quite relevant for this discussion. The bottom line is that the uncertainty is not a result of a perturbation of the object by the act of measurement, but rather an inherent property of quantum systems. Ars Technica again has an extremely lucid story on the study.

This brings us to the actual reason for this post, a research article which some say might be one of the most important results in quantum foundations in decades. The work itself is rather technical, but to sum it up, it offers solid evidence for the reality of the wavefunction, provided some rather modest assumptions hold. Nature News covered the publication while it was still in arXiv (that is, not yet peer reviewed and published) and later in a follow-up after the publication. Both news articles are well worth a read (pay attention to the evolution of the titles).

What prompted me to write about this now was the extremely interesting back story to the article and the news items, explained on the excellent Cosmic Variance blog in a guest post by one of the authors, Terry Randolph. It gives a rare peek behind the curtain of scientific method, illustrating (perhaps in a slightly negative light) the role of the editorial and peer review processes to what gets published and where. This stuff is extremely interesting to scientists, but perhaps it will be illuminating for the lay reader as well.

I'll likely have more to say on the topic from personal experience in the (hopefully) near future.