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 (coupler). This proposal operates essentially by employing a technique of a coupler 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 [Su et al, Sci. Rep.4, 3898 (2014)] requiring 2N steps of operation. Moreover, due to the use of only two resonators and a coupler, the experimental setup is much simplified when compared with previous proposals requiring three resonators and two superconducting qubits/qutrits.