Path integral contour deformations for noisy observables
William Detmold (Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA); Gurtej Kanwar (Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA); Michael L. Wagman (Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA, Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA); Neill C. Warrington (Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550, USA)
Monte Carlo studies of many quantum systems face exponentially severe signal-to-noise problems. We show that noise arising from complex phase fluctuations of observables can be reduced without introducing bias using path integral contour deformation techniques. A numerical study of contour deformations for correlation functions in Abelian gauge theory and complex scalar field theory demonstrates that variance can be reduced by orders of magnitude without modifying Monte Carlo sampling.
