Vacuum-selected timescales in driven Josephson systems

In this work, we demonstrate that the intrinsic timescale of a Josephson junction can be controlled through dynamical vacuum selection. By applying a Kapitza-like high-frequency drive to the system, the effective Josephson potential is reshaped, allowing for the stabilization of inphase or antiphase configuration. As a result, the Josephson plasma frequency, that is, the clock frequency of the junction, becomes a tunable property of the selected vacuum. Our findings establish a vacuum-controlled Josephson clock principle, in which the dynamical vacuum acts as an internal reference that fixes the operational timescale of Josephson oscillations, rather than this scale being imposed externally.