Two-qubit Gate of Combined Single Spin Rotation and Inter-dot Spin   Exchange in a Double Quantum Dot
  A crucial requirement for quantum information processing is the realization of multiple-qubit quantum gates. Here, we demonstrate an electron spin based all-electrical two-qubit gate consisting of single spin rotations and inter-dot spin exchange in a double quantum dot. A partially entangled output state is obtained by the application of the two-qubit gate to an initial, uncorrelated state. We find that the degree of entanglement is controllable by the exchange operation time. The approach represents a key step towards the realization of universal multiple qubit gates. 
R. Brunner, Y.-S. Shin, T. Obata, M. Pioro-Ladri\`ere, T. Kubo, K.   Yoshida, T. Taniyama, Y. Tokura, S. Tarucha
quant-ph