Suppressing gauge drift in quantum simulations with gauge transformations

The simulation of quantum lattice gauge theories faces the major challenge of maintaining gauge invariance because various errors in the simulation push the state of the system out of the physical subspace of the system's exponentially larger Hilbert space. This paper outlines a method, based off of previous work [Phys. Rev. A 110, 022417 (2024)], that uses gauge transformations in two ways. First, the method exploits the Zeno effect by conducting frequent projections to suppress gauge drift. These projections utilize local gauge transformations to destructively interfere unphysical amplitudes via coupling to an ancillary qubit while the physical amplitudes are left untouched, up to a less than unity normalization factor. Second, gauge transformations are conducted throughout the time evolution of the system to hamper the speed of gauge drift. This paper demonstrates this method on a pure one-dimensional SU(2) toy model.