Fast optical control of a coded qubit in a triple quantum dot

In this work, we study strategies for the optical control, within the dipole approximation, of a qubit encoded in the total intrinsic angular momentum states of three electrons confined in a triple quantum dot. The system is modeled using effective confining potentials, and its electronic structure is calculated using the configuration interaction method. Optimal control theory (OCT) was applied to design low-fluence time-dependent electric fields controlling the qubit in times shorter than a nanosecond. The resulting pulses produce transitions between the qubit states for experimentally available field amplitudes with high fidelity. Moreover, studying the dominant frequencies present in the OCT pulses, we show that the switching between the qubit states can also be achieved with simpler combinations of sinusoidal driving fields that produce transitions to intermediate states. The limitations of an extended Hubbard description for the model and its dynamic behavior are also discussed.