Figure 1

(Color online) (a) Schematic of qubit circuit, showing capacitances $C_1+C_2=C$; and (b) energy levels for qubit as a function of $V_x$, using parameters given in the text and showing energies for nominal bias point ${\Phi }_{x_0}=0.25{\Phi }_0$ (solid lines) and for extremes of the control modulation field ${\Phi }_{x_0}=(0.25\pm 0.05){\Phi }_0$ (dashed lines).Reuse & Permissions

Figure 2

(Color online) Fidelity ($F$, solid lines) and trace distance ($D$, dashed lines) achieved using guidance algorithm as a function of the voltage bias value for different values of $t_{max}:20$ qubit cycles (blue), 50 qubit cycles (green), and 100 qubit cycles (red); (a) target state is the excited state at nominal bias voltage, and (b) target state is an arbitrary state with $\theta =\pi ∕2$ and $\varphi =\pi ∕4$.Reuse & Permissions

Figure 3

(Color online) (a) Example trajectory of state on the Bloch sphere under proportional guidance with the excited state as the target state and $\Delta V_{x_0}=0.1\times 2e∕C$; and (b) control fields $\Delta V_{x_c}$ (green) and $\Delta {\Phi }_{x_c}$ (blue) as a function of the $t_{go}$, for example, trajectory in (a).Reuse & Permissions

Figure 4

(Color online) Fidelity ($F$, solid lines) and trace distance ($D$, dashed lines) achieved using guidance algorithm as a function of the voltage bias value for different time delays: zero time delay (blue), 0.125 qubit cycle delay (green), and 0.25 qubit cycle delay (red); target state is the excited state at nominal bias voltage and $t_{max}=50\mathrm{cycles}$.Reuse & Permissions

Figure 5

(Color online) (a) Fidelity ($F$, solid lines) and trace distance ($D$, dashed lines), and (b) purity ($p$, circles) achieved using guidance algorithm as a function of the voltage bias value for $\gamma =0.05∕\mathrm{cycle}$ and $\eta =0.0$ (no feedback, blue), $\eta =0.5$ (green), and $\eta =1.0$ (red); target state is the excited state at nominal bias voltage and $t_{max}=50\mathrm{cycles}$.Reuse & Permissions