  Scaling laws and universality play an important role in our understanding of
critical phenomena and the Kondo effect. Here we present measurements of
non-equilibrium transport through a single-channel Kondo quantum dot at low
temperature and bias. We find that the low-energy Kondo conductance is
consistent with universality between temperature and bias and characterized by
a quadratic scaling exponent, as expected for the spin-1/2 Kondo effect. The
non-equilibrium Kondo transport measurements are well-described by a universal
scaling function with two scaling parameters.
