TIFPA researcher exploits nanodevices to explore the foundations of Quantum Mechanics

Mar 8, 2016 Off Comments in Experiment by

The quantum superposition principle lies at the core of quantum mechanics. Particles, atoms and molecules can be prepared in fuzzy states which describe an object being at the same time in two different places. However, quantum theory dictates that when a measurement is performed, only one of the two options becomes real according to probabilistic rules, forcing the object to become localized. This so called collapse of the wavefunction is in apparent contradiction with the ordinary laws of quantum theory. Never ending debates developed around this problem since the birth of quantum mechanics, leading to different philosophical interpretations of the theory.

An elegant solution, known as spontaneous collapse models, was proposed 30 years ago by Italian physicists Ghirardi, Rimini and Weber. Collapse models postulate a breakdown of the quantum superposition principle due to random spontaneous localizations occurring at fundamental level, such that macroscopic objects of everyday life have always a definite position. In contrast with philosophical interpretations, collapse models can be experimentally tested, as their predictions are slightly different from those of quantum mechanics.

A new experimental test of collapse models has been recently reported in Physical Review Letters by TIFPA and FBK researcher Andrea Vinante, together with collaborators in Leiden and in Trieste. The basic idea is that collapse models imply, as a side-effect, a tiny violation of energy conservation, resulting in the spontaneous heating of a mechanical resonator. Accurate monitoring of a nanomechanical resonator at ultralow temperature has not revealed any significant heating, setting new stringent limits on the collapse rate. The new bound amounts to 1 collapse per century per atomic mass unit for a localization length of 1 micrometer, and is sufficient to disprove the most optimistic theoretical models.

This shows that current micromechanical technologies, combined with ultralow temperatures, can be used to explore the boundary between the quantum world and the classical everyday world. More performing devices available at TIFPA can potentially improve the current limit by at least two orders of magnitude.