Tuesday, December 17, 2013

Skepticism should be the default reaction to exotic claims

A good principle in science is "extra-ordinary claims require extra-ordinary evidence", i.e. the more exotic and unexpected the claimed new phenomena the greater the evidence needs to be before it should be taken seriously. A classic case is the recent CERN experiment claiming to show that neutrinos could travel faster than the speed of light. Surely it wasn't too surprising when it was found that the problem was one of detector calibration. Nevertheless, that did not stop many theorists from writing papers on the subject. Another case, are claims of "quantum biology".

About a decade ago some people tried to get me interested in some anomalous experimental results concerning elastic scattering of neutrons off condensed phases of matter. They claimed to have evidence for quantum entanglement between protons on different molecules for very short time scales and [in later papers] to detect the effects of decoherence on this entanglement. An example is this PRL which has more than 100 citations, including exotic theory papers stimulated by the "observation."

Many reasons led me not to get involved: mundane debates about detector calibration, a strange conversation with one of the protagonists, and discussing with Roger Cowley his view that the theoretical interpretation of the experiments was flawed, and of course, "extra-ordinary claims require extra-ordinary evidence"....

Some of the main protagonists have not given up. But the paper below is a devastating critique of their most recent exotic claims.

Spurious indications of energetic consequences of decoherence at short times for scattering from open quantum systems by J. Mayers and G. Reiter

Mayers is the designer and builder of the relevant spectrometer. Reiter is a major user. Together they have performed many nice experiments imaging proton probability distributions in hydrogen bonded systems.
They argue that the unexpected few per cent deviations from conventional theory that are "evidence" just arise from incorrect calibration of the instrument.


  1. Interesting topic. How would entanglement manifest in aggregates? The most prominent example are so called j-aggregates, which are characterized by a very specific signature change of the absorption/emission spectra.

    For me, entanglement is the e.g. the violation of Bell inequality. How is this related?

    1. Thanks for the comment.
      Indeed a definitive signature of entanglement is to observe violation of a Bell inequality.
      These experiments do nothing approaching that.

      Rather it is case of "quantum of the gaps", i.e. if we observe something we can't explain then we invoke an exotic quantum explanation.

      As you say in systems like J-aggregates one can see spectroscopic signatures can be explained in terms of coherent entangled exciton states.