  The nature of dark energy is one of the most outstanding problems in physical
science, and various theories have been proposed. It is therefore essential to
directly verify or rule out these theories experimentally. However, despite
substantial efforts in astrophysical observations and laboratory experiments,
previous tests have not yet acquired enough accuracy to provide decisive
conclusions as to the validity of these theories. Here, using a diamagnetically
levitated force sensor, we carry out a test on one of the most compelling
explanations for dark energy to date, namely the Chameleon theory, an
ultra-light scalar field with screening mechanisms, which couples to
normal-matter fields and leaves a detectable fifth force. Our results extend
previous results by nearly two orders of magnitude to the entire physical
plausible parameter space of cosmologically viable chameleon models. We find no
evidence for such a fifth force. Our results decisively rule out the basic
chameleon model as a candidate for dark energy. Our work, thus, demonstrates
the robustness of laboratory experiments in unveiling the nature of dark energy
in the future. The methodology developed here can be further applied to study a
broad range of fundamental physics.
