Room temperature test of the continuous spontaneous localization model using a levitated micro-oscillator

Abstract

Wave-function collapse models predict a tiny break of energy conservation via a weak spontaneous stochastic force acting on the system, and are attracting experimental studies. Among various physical systems, mechanical based methods provide a direct way to test such collapse induced force without any assumptions on its spectral characteristics. Levitated micro-mechanical oscillator has been recently proposed to be an ideal system. We demonstrated a micro-oscillator generated by a micro-sphere diamagnetically levitated in a magneto-gravitational trap under high vacuum. Due to the ultra-low mechanical dissipation and small mass, the oscillator provides a new upper bound on the wave-function collapse rate, two orders of magnitudes improvement over the previous bound in the same frequency range, and partially ruled out the enhanced collapse rate suggested by Adler. Being performed at room temperature, our experiment has already exhibited advantages over those methods operating at ultra-low temperatures previously reported. Our results experimentally show the potential of magneto-gravitational levitated mechanical oscillator as a promising method for searching wave-function collapse, and cryogenic experiments to further improvements are discussed.

Narrowing the Parameter Space of Collapse Models with Ultracold Layered Force Sensors

“…One would need a dramatic improvement of sensitivity and novel experi-mental techniques to fully probe the entire CSL parameter space. Recent advances in levitation technologies at low frequencies [37,48,49] combined with low temperatures and ultrahigh vacuum may be, together with more direct interferometric techniques on earth [18] and in space [50], the most promising route towards this ambitious goal.…”

“…They come from noninterferometric tests, which exploit an unavoidable indirect effect of collapse models, namely a tiny violation of the energy conservation [8]. Relevant examples are spontaneous X-ray emission from Germanium [19][20][21], spontaneous heating of massive bulk systems [22][23][24][25][26] or universal force noise on mechanical systems [27][28][29][30][31][32][33][34][35][36][37][38]. Bounds based on the first two effects are already ruling out Adler's parameters, but they can be easily evaded by reasonable assumptions on the spectrum of the CSL noise [22,39].…”

Ultralow Mechanical Damping with Meissner-Levitated Ferromagnetic Microparticles

“…This suggests that different levitation methods, such as Paul traps [28][29][30][31], or magnetic traps [32][33][34][35] could outperform optical levitation in applications requiring the lowest possible noise level. In particular, magnetic levitation appears very promising because of the unique combination of two properties: a completely passive trapping by static magnetic fields, and the possibility of using SQUIDs to detect the motion with ultralow power dissipation.…”

“…As a consequence it appears as the perfect solution for operation at low temperatures. Magnetic levitation can be implemented using diamagnetic [32,33] or superconducting particles [27] in external static fields, or ferromagnetic particles above superconductors [34,35]. Interestingly, these systems have been proposed not only for ultrasensitive force and inertial sensing [34,36], but also to test quantum mechanics in currently inaccessible regimes [4], to enable quantum technologies such as quantum magnetomechanics [27] and acoustomechanics [37] and for ultrasensitive magnetometry [11].…”

On quantum gravity tests with composite particles

“…(2). We argue that our bound on α can be improved further by moving a pendulum to a vacuum setup with optimised low damping suspension or by moving to diamagnetically levitated systems which exhibit extremely low damping rates 24,25 on earth and promise even better values when located in a space probe.…”