Nonequilibrium quantum working fluids: dynamics and usage

A quantum simulator is a technological concept that has been ideated with the scope of overcoming the hard computational problems that arise for simulating a quantum physical system with a classical computer. The problem is that the resources needed grow exponentially with the number of elementary constituents of quantum systems (qubits) which makes even relatively small quantum systems practically impossible to analyze in full detail. However, also ideal quantum simulators have their drawback: it seems extremely hard, if not impossible to obtain a reliable computation, which is arguably the main present challenge for the practical implementation of quantum computers. In fact, recently the acronym Noisy Intermediate-Scale Quantum (NISQ) devices has been coniated, which refers in particular also to simulators of quantum dynamics that, even if not fully solving the original problem, still give some advantage, perhaps used in hybrid schemes which involve quantum and classical resources. It is in this framework that the final goal of the present project situates: the idea is to construct a new set of tools that, once combined together, would form a quantum machine capable of simulating interesting non-equilibrium quantum physics, otherwise impossible to study with just classical computational methods. At the same time, the idea is not to construct something like a universal gate set or building a universal quantum computer, but rather to consider a thermodynamical-like setup, or in other words develop a machine based on a working (quantum) fluid. The idea is to use such a piston for improving immediately state-of-art experiments, for example through improved refrigeration limits and control over phase transitions in cold atoms. On top of that, we avoid the problem of certification of universal computation and only aim at verifying some important properties of the dynamics, e.g., field correlation functions, via improved data-analysis methods and ansatz reconstruction algorithms.