Constraining Dark Energy in Table-Top Quantum Experiments

If dark energy is a light scalar field, it might interact with normal matter. The interactions, however, are suppressed in the leading models, which are thus compatible with current cosmological observations as well as solar-system and laboratory studies. Such suppression typically relies on the scalar's interaction with macroscopic amounts of ordinary matter but can be bypassed by studying the interaction with individual particles.\footnote{C. Burrage, E. J. Copeland, E. A. Hinds, Probing dark energy with atom interferometry. J. Cosmol. Astropart. Phys. {\bf 2015,} 042 (2015).} Using an atom interferometer, we have placed tight constraints on so-called chameleon models, ruling out interaction parameters smaller than $2.3\times 10^{-5}$, while $M \sim 1$ or larger would lead to conflict with macroscopic experiments.\footnote{P. Hamilton, M. Jaffe, P. Haslinger, Q. Simmons, H. M\"uller, and J. Khoury, Atom-interferometry constraints on dark energy. Science {\bf 349,} 849 (2015).} In order to close this gap, we have already increased the sensitivity hundredfold and are expecting a new constraint soon. Purpose-built experiments in the lab or on the international space station will completely close the gap and rule out chameleons and other theories such as symmetrons or $f(R)$ gravity.