Fig. 3

Noise measurements. a Sketch of noise measurement at D2 when sourcing charge current from S2 b Sketch of thermoelectric measurement at D1 when sourcing from S2, the impinging current generates heat carried upstream by the neutral modes and converted to thermoelectric current at the QD. c Sketch of noise measurement at D2 when sourcing from H, the upstream neutral modes excited at the hot spot increase the Johnson–Nyquist noise measured at D2 d Conductance of the QPC as function of the split gate voltage. e Green: Current fluctuations measured at D2 when sourcing from S2 as function of the transmission of the QPC. Blue: Current fluctuations measured at D2 when sourcing from H. Black: Same as blue multiplied by a scaling factor α = 2. Red: Thermoelectric current measured at D1 when sourcing from S2. f Excess noise measured at D2 as function of the current at transmission half when sourcing from S2 (green) or H (blue). The black curve represents the noise from H to D2 (blue curve) multiplied by the scaling factor α = 2. g Gray dots: Shot noise contribution N _SN = N _tot − αN _th = N _S2→D2 − αN _H→D2. Orange curve: expected shot noise from two separated ballistic charge channels