Electric g tensor control and spin echo of a hole-spin qubit in a quantum dot molecule

The feasibility of high-fidelity single-qubit operations on a hole spin in a quantum dot molecule by electric g tensor control is demonstrated. Apart from a constant external magnetic field the proposed scheme allows for an exclusively electric control of the hole spin. Realistic electric gate bias profiles are identified for various qubit operations using process-tomography-based optimal control. They are shown to be remarkably robust against decoherence and dissipation arising from the interaction of the hole with host-lattice nuclear spins and phonons, with a fidelity loss of approximate to 1% for gate operation times of approximate to 10 ns. Spin-echo experiments for the hole spin are modeled to explore dephasing mechanisms and the role of pulse-timing imperfections in the gate fidelity loss is discussed.