Quantum Simulations of Strongly Correlated Electron Systems

We review recent progress in developing new quantum Monte Carlo methods for simulating strongly correlated electron systems. We then present a summary of our ongoing studies of the Hubbard model with these methods, including the ground-state constrained path Monte Carlo method and a new nite-temperature method. These methods make possible simulations at large system sizes and low temperatures. They eliminate the exponential decay of`sign' with system size and inverse temperature that is characteristic of the fermion sign problem in standard quantum Monte Carlo. The new methods, which are approximate, yielded accurate results in a variety of benchmarks. On the Hubbard model, our calculations have found no indication of long-range order in electron pairing correlations. An improved band structure in the model, derived from rst-principles calculations on YBa2Cu3O7, does not appear to enhance pairing.