Electrical conductors and insulators are at the basis of our current society, as they carry and store both energy and information. The conducting or insulating nature of materials is based on various separate ingredients of quantum nature, e.g. interactions, dimensionality, topology, disorder, etc. However, the complex interplay of such ingredients is in many cases still beyond our understanding. Notable examples are strongly-correlated superconductors and interacting topological materials. The reasons are that experiments on real materials aiming at separating the various ingredients are very difficult, and even that numerical simulations are inefficient, even for supercomputers.
With QUIC we aimed at a breakthrough in the understanding of the fundamental quantum mechanisms governing insulators and conductors by using quantum simulators, i.e. quantum computers of special purpose, based on fully controllable ultracold atomic gases. In an experiment-theory enterprise, we have engineered several different kinds of such synthetic quantum insulators and conductors, in which the various quantum ingredients are well known and can be controlled separately. Although in such neutral atomic systems the it is the mass and not the charge to be transported, they are governed by the same quantum laws of electrical conductors.
The immediate goal of QUIC has been the quantitative understanding of the subtle interplay of quantum phenomena. In some cases, we have proceeded towards the solution of long-standing open questions, such as the famous problem of Anderson localization or the existence of a paradoxical supersolid phase of matter. In other cases, we have tackled new conceptual problems, such as many-body localization, topological insulators and Majorana fermions. Our discoveries are already having an impact in the scientific community, and we are confident that theywill be very useful for the design of the quantum materials of tomorrow. In addition, we have extended the simulation capabilities of our atomic systems, through the realization of device-like systems that can simulate the behavior of the corresponding electronic and superconducting devices.
We are convinced that our work will have a long-lasting impact. The results of QUIC demonstrate also that there is still a lot of space for the discovery of new quantum phases based on novel types of interactions, topology, controlled disorder, etc. Indeed, several of the quantum simulators we have developed in QUIC are studying phenomena and systems that still do not exist in Nature. Understanding the new quantum phases with our quantum simulators will lead to the conception of new types of conductors and insulators.
