Fig. 1. Triple-quantum-dot device.

(A) Schematic diagram of a triple-dot device depicting the gate layout and the resulting electrostatic control of the potential landscape. Electrons are schematically depicted as yellow spheres. The lateral triple dot is formed underneath gates labeled P1, P2, and P3. Gates X1 and X2 affect the tunnel coupling (exchange) between dots P1 and P2 and dots P2 and P3, respectively. A local charge-sensing quantum dot is formed under the gate labeled M, whose tunnel rates to the bath are controlled by gates Z1 and Z2. The source of electrons for the system is provided by the two-dimensional electron gas (2DEG) formed under bath gates B1 and B2. Initialization and loading/unloading electrons from the outer dots (P1 and P3) to the 2DEG are controlled by the gates labeled T1 and T2. (B) Charge stability diagram of a triple dot in the (1,1,1) [P1,P2,P3] configuration plotted as a function of the DC bias applied to P3 versus P1. The grayscale in the plot is the current measured from the charge sensor created underneath the M gate shown in (A). The charge state of (1,0,1) bleeding into the (1,1,1) state occurs owing to the slow loading rate of the first electron in the middle dot (P2) relative to the scan rate of the plot. The red dotted line shows the P1 and P3 voltages used to define the detuning bias ε.