Monday, February 22, 2010

Polite physicists do not discuss this at dinner parties

I had some interesting but brief discussions today with Andrew Briggs about Tony Leggett's perspective on the quantum measurement problem. (see his Viewpoint in Science in 2005). Personally, I find Leggett's perspective a little extreme. I just think we need to have a more nuanced view of what "reality" is.
He considers three different views on the interpretation of Quantum Mechanics (QM):

(a) QM is the complete truth about the physical world, at all levels, and describes an external reality.

(b) QM is the complete truth (in the sense that it will always give reliable predictions concerning the nature of experiments) but describes no external reality.

(c) QM is not the complete truth about the world; at some level between that of the atom and that of human consciousness, other non–quantum mechanical principles intervene.

...... Personally, if I could be sure that we will forever regard QM as the whole truth about the physical world, I think I should grit my teeth and plump for option (b).


  1. I don't like the view of decoherence given in the Leggett article. He seems to be implying that decoherence is separate to QM, or somehow an interpretation. He also seems to be giving a greater significance to observation by a 'human agent' than the generic observation as an interaction with a macroscopic state / state with many modes.

    I also don't see any difference between (a) and (b). If no experiment can distinguish, what's the point? [Where as the difference between (b) and (c) implies some experimental difference.]

  2. 'I just think we need to have a more nuanced view of what "reality" is.'

    What does that mean?

  3. This question brings to mind the old adage 'The map in not the territory'.