Wednesday, 27 April 2016

Double slit is no longer proof of non-classical quantum behaviour!

Today it struck me again that the more then 50 years old position from Feynman about the double slit experiment:

"is impossible, absolutely impossible, to explain in any classical way" (1)

is still presented as being true in modern scientific and popular publications (2,5). In an earlier post I have already briefly discussed the experiments by Ives Couder (3), where he can mimic many quantum-like behaviors using macroscopic 'walkers' - tiny droplets bouncing on an silicon oil bath -, including the effects found for the double slit experiment.

Gerhard Grössing, from the Austrian Institute for Nonlinear Studies, has since then be working on simulating these pure classical behaviors. The most relevant publication in this context might be (4), where he summarizes:

"Despite claims in the literature that this scenario is to
be described by a dynamical nonlocality that could best be understood in the framework of the
Heisenberg picture, we show that an explanation can be cast within the framework of the
intuitively appealing Schrödinger picture as well"

The simulation (using individual particles at a time) reveals beautifully the interference bands of the dual split:

Within they're framework they explain how particles going individually through one of the slits can 'feel' whether or not the other slit is open or not. This is the paradox  Feynman stumbled over.

  1. Feynman, R.P., Leighton, R.B., and Sands, M. (1965). The Feynman Lectures in Physics Volume 3, Section 1–1, Addison–Wesley
  2. Quantum interference experiments, modular variables and weak measurements,Tollaksen et al, 2008,
  3. Single-Particle Diffraction andInterference ata Macroscopic Scale , Yves Couder, 2006,
  4. “Systemic Nonlocality” from Changing Constraints on
    Sub-Quantum Kinematics, Grössing et al, 2013,
  5. Life on the Edge: The Coming of Age of Quantum Biology (2014), Jim Al-Khalili et al.,