Mason Rhodes, Michael Kreshchuk, Shivesh Pathak (May 20 2024).
Abstract: Simulation of quantum systems of a large number of strongly interacting particles persists as one of the most challenging, and computationally demanding, tasks in classical simulation, involving both non-relativistic applications like condensed matter physics and quantum chemistry, as well as relativistic applications like lattice gauge theory simulation. One of the major motivations for building a fault-tolerant quantum computer is the efficient simulation of many-body systems on such a device. While significant developments have been made in the quantum simulation of non-relativistic systems, the simulation of lattice gauge theories has lagged behind, with state-of-the-art Trotterized simulations requiring many orders of magnitude more resources than non-relativistic simulation, in stark contrast to the similar difficulty of these tasks in classical simulation. In this work, we conduct an in-depth analysis of the cost of simulating Abelian and non-Abelian lattice gauge theories in the Kogut-Susskind formulation using simulation methods with near-optimal scaling in system size, evolution time, and error. We provide explicit circuit constructions, as well as T-gate counts and qubit counts for the entire simulation algorithm. This investigation, the first of its kind, leads to up to 25 orders of magnitude improvement over Trotterization in spacetime volume for non-Abelian simulations. Such a dramatic improvement results largely from our algorithm having polynomial scaling with the number of colors, as opposed to exponential scaling in existing approaches. Our work demonstrates that the use of advanced algorithmic techniques leads to dramatic reductions in the cost of ab initio simulations of fundamental interactions, bringing it in step with resources required for first principles quantum simulation of chemistry and condensed matter physics.