Disconnected contributions to hadronic structure: a new method for stochastic noise reduction

We present a new method for reducing the stochastic noise of all-to-all propagators based on stopping the inversion of the propagator before convergence. The method is easy to implement, unbiased and independent of the quark action. Applying this method to the calculation of disconnected loops needed for hadronic structure observables we find savings in computer time of factors of 4− 12 depending on the operator inserted in the loop. When combined with a hopping parameter expansion technique we obtain combined gains of up to factors of 30 for some operators.