Experimental Test of the Quantum Shot Noise Reduction Theory

The quantum suppression of shot noise predicted for mesoscopic conductors is observed using absolute measurements of the equilibrium and nonequilibrium electrical fluctuations of a quantum point contact. The small energy ( $30\char21{}600\mathrm{mK}$) and low frequency ( $1\char21{}10\mathrm{kHz}$) used for measurements allow for a reliable quantitative experimental confirmation of the quantum noise theory. The noise reduction factor is found to be in excellent agreement with theoretical expectations, evolving from nearly unity at low electronic wave transmission to nearly zero on a conductance plateau.