Indexed on: 29 Nov '16Published on: 29 Nov '16Published in: arXiv - Quantum Physics
Spontaneous collapse models predict that a weak force noise acts on any mechanical system, as a consequence of the collapse of the wave function. Significant upper limits on the collapse rate have been recently inferred from precision mechanical experiments, such as ultracold cantilevers and the space mission LISA Pathfinder. Here, we report new results from an experiment based on a high Q cantilever cooled to millikelvin temperature, potentially able to fully probe the Adler parameter range for the continuous spontaneous localization (CSL) model. High accuracy measurement of the cantilever thermal fluctuations reveal a nonthermal force noise of unknown origin. This excess noise is compatible with previous bounds on the CSL collapse rate, allowing to significantly extend the exclusion region. Several physical mechanisms able to explain the observed excess noise have been ruled out.