What is tested when experiments test that quantum dynamics is linear

TL;DR

This paper examines how experiments testing quantum linearity also implicitly test the influence of one system on another without interaction, challenging traditional assumptions about quantum dynamics.

Contribution

It highlights that testing for nonlinear quantum dynamics also probes the possibility of influence without interaction, a novel perspective on quantum experiments.

Findings

Nonlinear quantum dynamics could allow influence without interaction.

Experimental tests of linearity also test for non-traditional influences.

The possibility of influence without interaction remains an open question.

Abstract

Experiments that look for nonlinear quantum dynamics test the fundamental premise of physics that one of two separate systems can influence the physical behavior of the other only if there is a force between them, an interaction that involves momentum and energy. The premise is tested because it is the assumption of a proof that quantum dynamics must be linear. Here variations of a familiar example are used to show how results of nonlinear dynamics in one system can depend on correlations with the other. Effects of one system on the other, influence without interaction between separate systems, not previously considered possible, would be expected with nonlinear quantum dynamics. Whether it is possible or not is subject to experimental tests together with the linearity of quantum dynamics. Concluding comments and questions consider directions our thinking might take in response to this surprising unprecedented situation.