  Future communication and computation technologies that exploit quantum
information require robust and well-isolated qubits. Electron spins in III-V
semiconductor quantum dots, while promising candidates, see their dynamics
limited by undesirable hysteresis and decohering effects of the nuclear spin
bath. Replacing electrons with holes should suppress the hyperfine interaction
and consequently eliminate strong nuclear effects. Using picosecond optical
pulses, we demonstrate coherent control of a single hole qubit and examine both
free-induction and spin-echo decay. In moving from electrons to holes, we
observe significantly reduced hyperfine interactions, evidenced by the
reemergence of hysteresis-free dynamics, while obtaining similar coherence
times, limited by non-nuclear mechanisms. These results demonstrate the
potential of optically controlled, quantum dot hole qubits.
