  Microscopic current fluctuations are inseparable from conductance. We give an
integral account of both quantized conductance and nonequilibrium thermal noise
in one-dimensional ballistic wires. Our high-current noise theory opens a very
different window on such systems. Central to the role of nonequilibrium
ballistic noise is its direct and robust dependence on the statistics of
carriers. For, with increasing density, they undergo a marked crossover from
classical to strongly degenerate behavior. This is singularly evident where the
two-probe conductance shows quantized steps: namely, at the discrete
subband-energy thresholds. There the excess thermal noise of field-excited
ballistic electrons displays sharp and large peaks, invariably larger than shot
noise. Most significant is the nonequilibrium peaks' high sensitivity to
inelastic relaxation within the open system. Through that sensitivity,
high-current noise provides unique clues to the origin of quantized contact
resistance and its evolution towards normal diffusive conduction.
