Realization of quantum gates with multiple control qubits or multiple   target qubits in a cavity
  In this paper, we propose a scheme to realize three-qubit controlled phase gate and multiqubit controlled-NOT gate of one qubit simultaneously controlling n target qubit with four level quantum system in a cavity. Adjustment of level spacing during the gates implementation is not required. Implementation time for multiqubit controlled NOT gate is independent of number of qubit. Three-qubit phase gate is generalized to n-qubit phase gate with multiple control qubit and the number of steps (complexity) reduces linearly as compare to conventional gate decomposition method. Our scheme can be applied to various types of physical systems such as superconducting qubits coupled to resonator and trapped atoms in a cavity. Experimental possibility of our approach is also presented. 
Muhammad Waseem, Muhammad Irfan, and Shahid Qamar
quant-ph