Applicability of the ergodicity hypothesis to mesoscopic fluctuations

We evaluate a typical value of higher-order cumulants (irreducible moments) of conductance fluctuations that could be extracted from magnetoconductance measurements in a single sample when an external magnetic field is swept over an interval B-0. We find that the nth cumulant has a sample-dependent random part +/->(n/2)roota(n)B(c)/B-0, where > is the variance of conductance fluctuations, B-c is a correlation field, and a(n)similar ton! This means that an apparent deviation of the conductance distribution from a Gaussian shape, manifested by nonvanishing higher cumulants, can be a spurious result of correlations of conductances at different values of the magnetic field.