Controlled Quantum Operations of a Semiconductor Three-Qubit System
  The Coulomb interactions between electrons play important roles in coupling multiple qubits in various quantum systems. Here we demonstrate controlled quantum operations of three electron charge qubits based on three capacitively coupled semiconductor double quantum dots. The strong interactions between one double dot and other two double dots enable us to control the coherent rotations of one target qubit by the states of two control qubits. 
Hai-Ou Li, Gang Cao, Guo-Dong Yu, Ming Xiao, Guang-Can Guo, Hong-Wen   Jiang, and Guo-Ping Guo
cond-mat.mes-hall quant-ph