The split-ring Josephson resonator as an artificial atom

Using the resistive-shunted-junction model we show that a split-ring Josephson oscillator or radio-frequency SQUID in the hysteretic regime is similar to an atomic system. It has a number of stationary states that we characterize. Applying a short magnetic pulse we switch the system from one state to another. These states can be detected via the reflection of a small amplitude signal forming the base of a new spectroscopy.