Testing dissipative collapse models with a levitated micromagnet

A Vinante,H Ulbricht,G Gasbarri,C Timberlake,M Toroš

doi:10.1103/physrevresearch.2.043229

Abstract

We present experimental tests of dissipative extensions of spontaneous wave function collapse models based on a levitated micromagnet with ultralow dissipation. The spherical micromagnet, with radius $R=27$ $\mu$m, is levitated by Meissner effect in a lead trap at $4.2$ K and its motion is detected by a SQUID. We perform accurate ringdown measurements on the vertical translational mode with frequency $57$ Hz, and infer the residual damping at vanishing pressure $\gamma/2\pi<9$ $\mu$Hz. From this upper limit we derive improved bounds on the dissipative versions of the CSL (continuous spontaneous localization) and the DP (Di\'{o}si-Penrose) models with proper choices of the reference mass. In particular, dissipative models give rise to an intrinsic damping of an isolated system with the effect parameterized by a temperature constant; the dissipative CSL model with temperatures below 1 nK is ruled out, while the dissipative DP model is excluded for temperatures below $10^{-13}$ K. Furthermore, we present the first bounds on dissipative effects in a more recent model, which relates the wave function collapse to fluctuations of a generalized complex-valued spacetime metric.

Highlights

Spontaneous wave function collapse models [1,2,3,4,5,6] are a well-established approach in the context of quantum foundations
The motion of the microsphere is detected by a commercial DC superconducting quantum interference device (SQUID) connected through a single pickup coil placed above the levitated particle
The error bar on each point is calculated by adding in quadrature the mean amplitude of the peak when it is dominated by noise

Summary

Introduction

Spontaneous wave function collapse models [1,2,3,4,5,6] are a well-established approach in the context of quantum foundations. The key idea is that the unitary evolution of standard quantum mechanics must be modified by additional phenomenological terms in order to explain the emergence of definite and stochastic outcomes in measurement processes. It has been suggested that collapse models could be related to the long-standing problem of the incompatibility between quantum mechanics and general relativity [7]. In this latter respect, other related phenomenological models have been investigated recently [8,9,10,11]

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Conclusion