Figure 1

All data in this figure are acquired using about a 74 kHz driving frequency on the SET. (a) Schematic diagram of AC-HBT and SEM image of the double quantum dot (DQD) device. Areas of electron accumulation are indicated by false color highlighting of enhancement gates. The charge sensor used to measure the DQD state is in the upper left quadrant, whose source is connected to an AC + DC signal generator, and whose drain is connected to a cryogenic AC-coupled HBT amplification stage. Values of the passive elements are R_B = 1 MΩ, R_S = 100 kΩ, and C = 10 nF. (c) Circuit gain and sensitivity vs. power dissipated by the AC-HBT. (d) Normalized CB peak for different AC-HBT gain/power biases. The the blockade region of the CB peak reaches zero current. (e) Noise referred to the collector of the AC-HBT for different powers. The measured noise is plotted as blue points. The noise floor of the fridge (purple) (see Section VI in Supplementary Information), shot noise of the base (orange), collector (yellow), SET (light blue), Johnson noise of the shunt resistor (green), and total estimated noise (dark red) are plotted as solid lines.