  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.
