Effect of a voltage probe on the phase-coherent conductance of a ballistic chaotic cavity

The effect of an invasive voltage probe on the phase-coherent conduction through a ballistic chaotic cavity is investigated by random-matrix theory. The entire distribution P(G) of the conductance G is computed for the case that the cavity is coupled to source and drain by two point contacts with a quantized conductance of 2e²/h, both in the presence ({β}=1) and absence ({β}=2) of time-reversal symmetry. The loss of phase coherence induced by the voltage probe causes a crossover from P(G){∝}G^-1+β/2 to a Gaussian centered at G=e²/h with a {β}-dependent width.