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 temperatures, which is potentially able to improve the current bounds on the continuous spontaneous localization (CSL) model by 1 order of magnitude. High accuracy measurements of the cantilever thermal fluctuations reveal a nonthermal force noise of unknown origin. This excess noise is compatible with the CSL heating predicted by Adler. Several physical mechanisms able to explain the observed noise have been ruled out.

中文翻译：

---

使用超冷悬臂的崩溃模型的改进非干涉测试

自发崩溃模型预测，由于波动函数的崩溃，弱力噪声会作用于任何机械系统上。最近已经通过精密机械实验（例如超冷悬臂和太空任务LISA探路者）推断出了坍塌率的重要上限。在这里，我们报告了一项基于高水平的实验的新结果，$问$悬臂冷却至毫微卡尔文温度，这有可能将连续自发局域（CSL）模型上的电流范围提高1个数量级。悬臂热波动的高精度测量揭示了未知来源的非热力噪声。这种多余的噪声与Adler预测的CSL加热兼容。排除了能够解释观察到的噪声的几种物理机制。