Speaker
Description
We present a continuous-time path-integral Monte Carlo method for computing the low-lying spectrum of generic quantum lattice Hamiltonians, motivated in part by applications to qubit regularizations of quantum field theories. The method is based on projecting the thermal density matrix, $e^{-\beta H}$, onto a subspace spanned by a chosen set of linearly independent states. It is free of Trotter discretization errors and systematically converges, with increasing $\beta$, to low-energy states that have finite overlap with the projection subspace. While most effective for systems without a sign problem, it can also provide information about low-energy spectra of systems with sign-problems. Some applications are presented to illustrate the method.