We know of Christof Wetterich because much cited by Martin Reuter in papers about Asymptotic Safe approach to quantum gravity (invited talks at Loops 2005, Loops 2007, and other QG conferences.) But actually Wetterich has a much broader reputation. So here is my puzzle. It seems unlikely that anyone could derive QM from classical statistical physics. If it were valid wouldn't this give a deeper understanding of the foundations. Kind of thing 't Hooft has asked for in Chapter 2 of Oriti's book. Can this thing of Wetterich be right? Is there some catch? I hope some other people can help out here. http://arxiv.org/abs/0906.4919 Quantum mechanics from classical statistics Christof Wetterich 31 pages (Submitted on 26 Jun 2009) "Quantum mechanics can emerge from classical statistics. A typical quantum system describes an isolated subsystem of a classical statistical ensemble with infinitely many classical states. The state of this subsystem can be characterized by only a few probabilistic observables. Their expectation values define a density matrix if they obey a 'purity constraint'. Then all the usual laws of quantum mechanics follow, including Heisenberg's uncertainty relation, entanglement and a violation of Bell's inequalities. No concepts beyond classical statistics are needed for quantum physics - the differences are only apparent and result from the particularities of those classical statistical systems which admit a quantum mechanical description. Born's rule for quantum mechanical probabilities follows from the probability concept for a classical statistical ensemble. In particular, we show how the non-commuting properties of quantum operators are associated to the use of conditional probabilities within the classical system, and how a unitary time evolution reflects the isolation of the subsystem. As an illustration, we discuss a classical statistical implementation of a quantum computer." I just checked Spires and Wetterich has 5 papers of topcites 250+ class. He has 258 published papers in Spires and 18 of them are in the 100+ cites category. His home is the Heidelberg ITP. I mention this in case someone needs these objective measures. My awareness of him is that his work forms the basis for one of a halfdozen active live non-string approaches to QG (where you find a UV fixed point in the renormalization group flow---idea proposed by Steven Weinberg and carried out by Reuter Percacci Litim and others. This approach, like Loll's and Horava's also shows a decline in dimensionality from 4D towards 2D with scale---the spatial and space-time dimension runs.) Because Wetterich is at the root of a live approach to QG, he is a big deal for me. But I don't know how to evaluate what he says about deriving QM from statistical physics. It seems too cute to be true. Can anyone put this in perspective for me?