Noninterferometric experiments have been successfully employed to constrain models of spontaneous wave function collapse, which predict a violation of the quantum superposition principle for large systems. These experiments are grounded on the fact that, according to these models, the dynamics is driven by noise that, besides collapsing the wave function in space, generates a diffusive motion with characteristic signatures, which, though small, can be tested. The noninterferometric approach might seem applicable only to those models that implement the collapse through noisy dynamics, not to any model, that collapses the wave function in space. Here, we show that this is not the case: under reasonable assumptions, any collapse dynamics (in space) is diffusive. Specifically, we prove that any space-translation covariant dynamics that complies with the no-signaling constraint, if collapsing the wave function in space, must change the average momentum of the system and/or its spread.

中文翻译：

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塌陷动力学是扩散的

非干涉实验已成功用于约束自发波函数塌缩模型，该模型预测大型系统会违反量子叠加原理。这些实验基于这样一个事实：根据这些模型，动力学是由噪声驱动的，噪声除了使空间中的波函数塌陷之外，还产生具有特征特征的扩散运动，尽管特征特征很小，但可以进行测试。非干涉方法似乎只适用于那些通过噪声动力学实现坍缩的模型，不适用于任何使空间中的波函数坍缩的模型。在这里，我们证明情况并非如此：在合理的假设下，任何塌陷动力学（在空间中）都是扩散的。具体来说，我们证明任何符合无信号约束的空间平移协变动力学，如果使空间中的波函数塌陷，则必须改变系统的平均动量和/或其扩散。