Stochastic Estimations of Fermion Matrix Determinants with Unbiased Subtractions

The Padé-Z₂ stochastic estimator is used to calculate the fermion matrix determinants and the determinant ratios with an unbiased variational scheme. The results on an 8³ x 12 lattice with Wilson action show that the determinant ratio with a relatively small number of Z₂ noises (e.g., 400) can be estimated by using the unbiased subtractions.