One-Step Generation of Multi-Qubit GHZ and W States in Superconducting Transmon Qubit System

We propose a one-step method to prepare multi-qubit GHZ and W states with transmon qubits capacitively coupled to a superconducting transmission line resonator (TLR). Compared with the scheme firstly introduced by Wang et al. [ Phys. Rev. B 81 (2010) 104524 ], our schemes have longer dephasing time and much shorter operation time because the transmon qubits we used are not only more robust to the decoherence and the unavoidable parameter variations, but also have much stronger coupling constant with TLR. Based on the favourable properties of transmons and TLR, our method is more feasible in experiment.