Multiqubit quantum phase gate using four-level superconducting quantum   interference devices coupled to superconducting resonator
  In this paper, we propose a scheme to realize three-qubit quantum phase gate of one qubit simultaneously controlling two target qubits using four-level superconducting quantum interference devices (SQUIDs) coupled to a superconducting resonator. The two lowest levels |0> and |1> of each SQUID are used to represent logical states while the higher energy levels |2> and |3> are utilized for gate realization. Our scheme does not require adiabatic passage, second order detuning, and the adjustment of the level spacing during gate operation which reduce the gate time significantly. The scheme is generalized for an arbitrary n-qubit quantum phase gate. We also apply the scheme to implement three-qubit quantum Fourier transform. key words: quantum phase gate, superconducting quantum interference devices (SQUIDs), superconducting resonator, quantum Fourier transform 
Muhammad Waseem, Muhammad Irfan, Shahid Qamar
quant-ph cond-mat.supr-con