Introduction.- Quantum Dot Spin Qubits.- Ultrafast Control of Electron Spins.- Hadamard Gate.- Geometric Phase Gates.- Hole Spin Qubits.- Spin-Photon Entanglement.- Conclusion and Outlook.- A: Fidelity Analysis.- B: Electron Spin-Nuclear Feedback.- C: Heavy-Hole-Light-Hole Mixing.- D: Coherent Hole Rotation Model.- E: Hole Spin Device Design.- F: Visibility of Quantum Erasure.