Can one extract key properties of atomic nuclei by studying the seemingly unrelated system of a few cold, interacting atoms in a quantum gas? The answer is a resounding yes. The reason for that unexpected connection, which links energies spanning some 18 orders of magnitude, can be traced to universality in few-body physics, the focus of this article. In some cases, studies of systems with just two, three, or four atoms have even helped researchers identify fundamental aspects of a degenerate quantum gas having more than 100 000 particles.
Experimental studies of universality in nuclei are difficult because the nuclear force cannot easily be changed in the laboratory. For cold-atom systems, however, there exists a regime in which a key parameter, the scattering length, can be readily manipulated. (The scattering length a is defined in terms of the low-energy S-wave scattering phase shift δ by a -lim k→...
