Fig. 1
Description of the experimental device and methods. a Scanning electron microscope (SEM) image of the device. In this configuration, the current is sourced from S1, reaching to the quantum dot (QD). Sweeping the plunger gate voltage results in a succession of Coulomb peaks as shown by the blue curve on g. b Schematic of the equilibrium distribution on each side of the QD. When the plunger gate is tuned, electron can tunnel into the dot from the high occupation number region to the lower one, creating a positive current measured at D1. c Neutral mode heat detection configuration: The current sourced in H is directed to the ground and plays no part in the experiment. A hot spot present at the upstream side of contact H excites the neutral heat modes flowing upstream toward the QD, creating a thermal gradient across the QD. The produced thermoelectric current then flows to D1. d Sketch of the equilibrium distribution on both side of the dot in the case depicted in c. In this case, the tunneling direction will depend if an energy level of the QD is placed below or above the center of the distribution. This induces an alternating current when the plunger gate is tuned. e Noise measurement configuration: Here the input QPC of the QD is set to half transmission while the second one is fully open. This turns the QD into an effective single QPC device. The heat carried by the neutral modes increase the electron temperature at the input QPC of the dot, which increases the Johnson–Nyquist noise, measured at D1. f Excess noise measured at D1 as function of current injected in H, as described in e. g Measurement corresponding to the configuration a in blue and c in orange
