Four major breakthroughs are achieved while working on QuStA:
a) By tuning the interactions between the constituting atoms, QuStA could observe how a system of up to 12 trapped atoms transitions from one with normal conducting properties to one where transport is possible without any resistance. The precursor of a phase transition between a normal- and a superfluid was observed.
b) To test what is exactly the mechanism behind this phase transition, the researchers started to look into the correlations that might be responsible, for which they had to devise a new method to detect each and every single particle. To test this method, they used it on a system of noninteracting fermionic atoms, which obey the Pauli principle also known from chemistry. As of these particles only one can occupy a quantum state at a time. This is how they form what is called a Pauli crystal, even though there is literally no interaction between them. QuStA could for the first time observe such a crystal.
c) Taking the Pauli crystals and turning attractions on between opposite spin states, correlations between atoms could be revealed that resemble very much the so-called Cooper pairs, a paradigmatic quantum mechanism that is behind superconductivity in real materials.
d) By observing the time evolution of an initially elliptic cloud, fluid behavior could be found in a system consisting of only ten atoms, contrary to contemporary teaching in text books, that describe fluids as macroscopic objects.
