Quantum simulation of ordering above critical temperature from many-body dynamics

The previous two decades have seen the development of highly controlled clouds of atoms, prepared at a few billionth degree above absolute zero in a vacuum, to act as effective analog quantum computers. Often termed quantum simulators, these systems work by confining those ultracold atoms using lasers in a variety of ways, and precisely controlling the manner in which the atoms move and interact with each other. This has already allowed these systems to address fundamental problems in solid state and other areas of physics beyond the capacities of classical computers. Of those problems, one that is intensely researched is how to force materials to exhibit fundamentally and technologically important ordering, such as superfluidity, superconductivity and Mott insulation, even above the critical temperature at which these orders appear in equilibrium. In this context, the previous decade has seen the emergence of an exciting line of research in solid-state physics that claims the observation of signatures of short-lived, light-induced superconducting states well above the critical temperature. In that approach, materials prepared to be initially above the critical temperature, and thus not in a superconducting state, are pushed out of equilibrium and potentially superconducting signatures are recorded afterwards. These experiments offer the prospect of near-room-temperature superconducting states without pressurisation. However, these findings are contested, as a fundamental understanding of the underlying processes is currently lacking, and there is not even the most basic quantitative many-body theory on such dynamic orders in 2D and 3D systems. In parallel, analogous problems have emerged in research using ultracold atoms, which is aimed at the fundamentals of non-equilibrium many-body physics, and asks to what extent ordered states can emerge out of many-body dynamics when rapidly changing a system parameter that would control a phase transition at equilibrium. The limited progress on all these challenges is due to the outstanding difficulty of computing the real-time evolution of non-equilibrium many-body quantum systems in 2D and 3D using classical algorithms. The present project will use ultracold atomic lattice gases as effective analog quantum computers that can far outperform classical digital ones. These will allow for a quantitative simulations of whether and how superconducting, superfluid and insulating orders above the equilibrium critical temperature could be induced via out-of-equilibrium dynamics in condensed-matter systems. These studies are now possible due to significant advances by the investigators, both in experiments on ultracold atoms, and in state-of-the-art theory for out-of-equilibrium evolution of quenched many-body systems in 2D and 3D. This project will enable the first validation of the quantum simulator’s output on the time scales, system sizes and temperatures of ordered states above the critical temperature generated from out-of-equilibrium many-body dynamics.