  We reveal for the first time by experiments that within a narrow parameter
regime, two cavitation bubbles with identical energy generated in anti-phase
develop a supersonic jet. High-resolution numerical simulation shows a
mechanism for jet amplification based on toroidal shock wave and bubble necking
interaction. The micro-jet reaches velocities in excess of 1000 m/s. We
demonstrate that potential flow approximation established for Worthington jets
accurately predicts the evolution of the bubble gas-liquid interfaces.
