Fig. 1: Electrostatic quantum dots with tunable exchange.
From: Assessment of the errors of high-fidelity two-qubit gates in silicon quantum dots
a, False colour scanning electron micrograph (SEM) of a device similar to A and B The qubit dots are accumulated under the plunger (P) gates. The charge state of the double dot is monitored, by the sensor dot which is confined between the barrier gates SLB and SRB. b, False colour transmission electron micrograph (TEM) of a cross-section of a device similar to A and B. The shaded area shows the extension of electron wave functions under each dot. c, Charge stability map of device A in isolated mode together with the important operation points for qubit operation (Jon and Joff) and readout (RO). d, Exchange energy for devices A, B and C as a function of VJ. The rate of increase of exchange is shown in the legend. e, CZ oscillations using the measurement sequence in g with two different control qubit initializations at a fixed level of J. f, Oscillations of DCZ gate sequence as a function of J-gate pulse time and voltage level. g, Pulse sequences used in the experiments for CZ (left) and DCZ (right) in e and f. Here, ‘X’ refers to \(\frac{\uppi }{2}\) rotation around the x axis. For the CZ gate we apply phase θ rotations around z-axis for both qubits to correct for the Stark shift from pulsing the J-gate.
