[1] The experimental evidence for diffraction through slits has been disputed,[2][3] however, though the diffraction pattern of walking droplets is not exactly the same as in quantum physics, it does appear clearly in the high memory parameter regime (at high forcing of the bath) where all the quantum-like effects are strongest.
[7][8][9][10][11] Besides being an interesting means to visualise phenomena that are typical of the quantum-mechanical world, floating droplets on a vibrating bath have interesting analogies with the pilot wave theory, one of the many interpretations of quantum mechanics in its early stages of conception and development.
The Copenhagen interpretation does not use the concept of the carrier wave or that a particle moves in definite paths until a measurement is made.
Floating droplets on a vibrating bath were first described in writing by Jearl Walker in a 1978 article in Scientific American.
[13] In 2005, Yves Couder and his lab were the first to systematically study the dynamics of bouncing droplets and discovered most of the quantum mechanical analogs.
John Bush and his lab expanded upon Couder's work and studied the system in greater detail.
That is, the droplet does not simply bounce in a stationary position but instead wanders in a straight line or in a chaotic trajectory.
When a droplet interacts with the surface, it creates a transient wave that propagates from the point of impact.
Light has wave-like behavior, and interferes with itself through the slits, creating a pattern of alternating high and low intensity.
In 2006, Couder and Fort demonstrated that walking droplets passing through one or two slits exhibit similar interference behavior.
[18] It has since been shown that droplet trajectories are sensitive to interactions with container boundaries, air currents, and other parameters.
Though the diffraction pattern of walking droplets is not exactly the same as in quantum physics, and is not expected to show a Fraunhofer-like dependence of the number of peaks on the slit width, the diffraction pattern does appear clearly in the high memory regime (at high forcing of the bath).
However, surprisingly, sometimes the walking droplet would bounce past the barrier, similar to a quantum particle undergoing tunneling.
In fact, the crossing probability was also found to decrease exponentially with increasing width of the barrier, exactly analogous to a quantum tunneling particle.
That is, the energy levels of the bound state are not continuous and only exist in discrete quantities, forming “quantized orbits.” In the case of a hydrogen atom, the quantized orbits are characterized by atomic orbitals, whose shapes are functions of discrete quantum numbers.
The stable orbiting droplets analogously represent a bound state in the quantum mechanical system.