Efficient scheme for generation of photonic NOON states in circuit QED
  We propose an efficient scheme for generating photonic NOON states of two resonators coupled to a four-level superconducting flux device. This proposal operates essentially by employing a technique of a coupler device resonantly interacting with two resonators simultaneously. As a consequence, the NOON-state preparation requires only $N+1$ operational steps and thus is much faster when compared with a recent proposal [Q. P. Su et al., Scientific Reports 4, 3898 (2014)] requiring $2N$ steps of operation. Moreover, due to the use of only two resonators and a device, the experimental setup is much simplified when compared with previous proposals requiring three resonators and two superconducting qubits/qutrits. 
Shao-Jie Xiong, Zhe Sun, Jin-Ming Liu, Tong Liu, Chui-Ping Yang
quant-ph