Efficient engineered-dissipation algorithms for many-body ground and thermal states preparation

Preparation of quantum ground and thermal states of many-body systems is a key computational challenge for quantum simulation, with applications in physics, chemistry, and classical optimization. We will describe simple and efficient algorithms for ground and thermal state preparation, combining engineered bath resetting and modulated system-bath coupling to derive a quantum channel approximately satisfying quantum detailed balance relations. We will show that the fixed point of the channel approximates the Gibbs state with a controlled error. We will illustrate the cooling mechanism by developing a kinetic-theory description, which yields quantiative predictions for cooling rates for systems with well-defined quasiparticles. Further, we provide extensive numerics for one- and two-dimensional systems, confirming that the protocol successfully prepares ground and thermal state throughout the finite-temperature phase diagrams, including near the quantum phase transition. Our algorithm provides a path to efficient quantum simulation of quantum-correlated states with current and near-term quantum processors.