In quantum mechanics a central mystery has been why small chunks of matter tend to behave like particles and sometimes like waves.
Past theories have subscribed to what is called the "Copenhagen interpretation," which holds that a particle is a wave "smeared out" across the universe that collapses into a determined location only when observed, MIT reported. Some researchers have come up with an alternative interpretation dubbed the "pilot-wave theory," which suggests quantum particles are born along a wave and have definite trajectories, but still exhibit wavelike statistics because of the pilot wave's influence.
Researchers recently discovered a macroscopic pilot-wave system whose statistical behavior recalls that of quantum systems. The system consists of a bath of fluid vibrating at a rate just below the threshold at which waves form on its surface. When a droplet of the same fluid is released and strikes the surface it causes the wave to radiate outwards. The droplet then moves across the bath, propelled by the waves it creates.
"This system is undoubtedly quantitatively different from quantum mechanics," Bush says. "It's also qualitatively different: There are some features of quantum mechanics that we can't capture, some features of this system that we know aren't present in quantum mechanics. But are they philosophically distinct?" asked John Bush, a professor of applied mathematics at MIT.
Bush believes the Copenhagen interpretation overlooks the technical challenge of calculating particles' trajectories by denying their existence.
"The key question is whether a real quantum dynamics, of the general form suggested by de Broglie and the walking drops, might underlie quantum statistics," he said. "While undoubtedly complex, it would replace the philosophical vagaries of quantum mechanics with a concrete dynamical theory."
Last year Bush and student Jan Molacek derived an equation relating the dynamics of the pilot wave to the particles' trajectories. The researchers had two advantages of quantum pioneers; the bouncing droplet was plainly visible allowing them to accurately determine its location, and the employment of the chaos theory. The theory holds that "many macroscopic physical systems are so sensitive to initial conditions that, even though they can be described by a deterministic theory, they evolve in unpredictable ways," MIT reported. The researchers applied their pilot-wave theory to show how chaotic pilot-wave dynamics lead to quantumlike statistics.
"The work of Yves Couder and the related work of John Bush ... provides the possibility of understanding previously incomprehensible quantum phenomena, involving 'wave-particle duality,' in purely classical terms," said Keith Moffatt, a professor emeritus of mathematical physics at Cambridge University. "I think the work is brilliant, one of the most exciting developments in fluid mechanics of the current century."
The findings were published in the Annual Review of Fluid Mechanics.
