Digital Quantum Simulation for Energy Spectroscopy of Schwinger Model

This talk will discuss a method to efficiently compute energy spectra in lattice quantum field theories by digital quantum simulation. A quantum algorithm called coherent imaging spectroscopy quenches the ground state with a time-oscillating perturbation for various frequencies. It reads off excited energy levels from values of frequencies showing the loss of the vacuum-to-vacuum probability following the quench. I will demonstrate this algorithm for the Schwinger model which is the (1+1)-dimensional quantum electrodynamics with a topological term. During the simulation, the ground state of the Schwinger model on lattice is prepared by adiabatic state preparation and various types of quenches to the approximate ground state are applied via Suzuki-Trotter time evolution. The computational complexity estimation for physically reasonable results likely implies the efficiency of the method in the early fault-tolerant quantum computer era.