Classical to quantum crossover in high-current noise of one-dimensional ballistic wires

Microscopic current fluctuations and conductance are inseparable. We present a unified kinetic theory of both quantized conductance and nonequilibrium noise in one-dimensional ballistic wires. We show that high-current ballistic fluctuations depend, directly and robustly, on carrier statistics. This is dramatically evident in the large noise peaks predicted to coincide with the quantized steps in the two-probe conductance. The outstanding features of nonlinear ballistic fluctuations are: (i) their observability by standard experimental techniques; (ii) their strong suppression by electron degeneracy; (iii) their divergence in any model that ignores the explicit dynamics of dissipative scattering in the macroscopic leads; (iv) their numerical dominance over the noise predictions of the Landauer-Buttiker model. The nonequilibrium noise of hot ballistic carriers is strikingly sensitive to their inelastic energy loss on entering the leads. Uniquely and quantitatively, it characterizes the observed nonideality of quantized conductance.