The sign(al-to-noise) problem

Abstract: A fundamental feature of quantum mechanics is that probability amplitudes are complex numbers. I will explain how this manifests in lattice QCD and quantum Monte Carlo calculations as the notorious "sign problem," which is what currently prevents lattice QCD from efficiently predicting the structure and dynamics of large nuclei. I will then present my recent work to obtain two-sided spectral bounds on hadron masses and hadron-hadron scattering amplitudes that provide rigorous QCD predictions even when the spectrum is dense and sign(al-to-noise) problems are severe, as well as ongoing efforts to understand and turn down the noise.