  Numerical studies of quantum field theories usually rely upon an accurate
determination of stochastically estimated correlation functions in order to
extract information about the spectrum of the theory and matrix elements of
operators. The reliable determination of such correlators is often hampered by
an exponential degradation of signal/noise at late time separations. We
demonstrate that it is sometimes possible to achieve significant enhancements
of signal/noise by appropriately optimizing correlators with respect to the
source and sink interpolating operators, and highlight the large range of
possibilities that are available for this task. The ideas are discussed for
both a toy model, and single hadron correlators in the context of quantum
chromodynamics.
