Getting Round The Uncertainty Principle

From BBC Science & Environment:

Researchers have bent one of the most basic rules of quantum mechanics, a counterintuitive branch of physics that deals with atomic-scale interactions. Its “complementarity” rule asserts that it is impossible to observe light behaving as both a wave and a particle, though it is strictly both. In an experiment reported in Science, researchers have now done exactly that.

See also Physics World:

An international team of researchers has, for the first time, mapped complete trajectories of single photons in Young’s famous double slit experiment. The finding takes an important first step towards measuring complimentary variables of a quantum system – which until now has been considered impossible as a consequence of the Heisenberg uncertainty principle.

Picture above (from Physics World):

This 3D plot shows where a quantum particle is most likely to be found as it passes through double-slit apparatus and exhibits wave-like behaviour. The lines overlaid on top of the 3D surface are the experimentally reconstructed average paths that the particles take through the experiment. (Courtesy: Krister Shalm and Boris Braverman).


  1. Richard Berry says:

    Very interesting, but I do have difficulty with the (BBC) statement “…though it is strictly both.”. Light may behave as if it was a wave or a particle, or both but surely these are just models. For any model of an aspect of reality the “fidelity” of the model cannot be 100%; otherwise it is reality. To say “…strictly it is both” dismissively asserts as fact something that isn’t necessarily so.

    1. David Pottinger says:

      Richard, thanks for the interest and comment.

      The general equations of quantum theory were written down in the 1920’s and have not yet yielded any inconsistencies in comparison with (a huge number of) experiments. This is extremely impressive and in this sense the foundations of the approach/model are ‘high fidelity’. The problems arise in the interpretation of the theory and there are different schools of thought on this.

      One issue is the attempt to understand effects at very small scales using concepts (waves, particles) that have been developed at a totally different scale. At one point someone even suggested we call quantum objects ‘wavicles’ to emphasise that they are not one or the other but can behave as one or the other in different circumstances. I think this complex situation is what the BBC article was trying to communicate and probably a little too succinctly!

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