A study reveals that two cavitation bubbles, generated in anti-phase with identical energy, can produce supersonic micro-jets. High-resolution simulations show that the jet amplification is driven by interactions between toroidal shock waves and bubble necking. The micro-jet reaches velocities exceeding 1000 m/s. The research demonstrates that potential flow approximations accurately predict the evolution of bubble gas-liquid interfaces. The study focuses on the dynamics of anti-phase bubble pairs with identical maximum radii. The second bubble is initiated when the first is at its maximum size, leading to fast jets with velocities up to 1400 m/s. The jet remains stable and penetrates the gas-liquid interface without atomizing. The experimental setup involves generating bubbles in deionized water using pulsed lasers. High-speed imaging and numerical simulations are used to analyze the bubble dynamics. The simulations use a high-order finite-volume method to solve the Navier-Stokes equations, capturing the interface between the bubble and liquid. The results show that the jet velocity reaches up to 3000 m/s immediately after ejection, reducing to 1200 m/s before impacting the second bubble. The jet remains at a reduced speed of 250 m/s after penetrating the second bubble. The supersonic velocity of the collapsing neck forms a conical shock wave inside the bubble, with a half-angle of 16 degrees, implying a jet velocity of about 3.6 times the speed of sound. The study identifies that the ultra-fast needle jet forms only in a narrow range of standoff distances (0.7 < γ < 0.8). Outside this range, the jet does not form due to insufficient energy focusing or unstable neck breakup. The mechanism involves the collapse of the elongated neck of the second bubble, leading to the emission of a shock wave that amplifies the jet velocity. The findings suggest that such supersonic jets could improve technical applications, such as needle-free injections. From a fundamental perspective, the mechanism offers a path to focus kinetic liquid energy through collective and resonant inertial cavitation bubble dynamics. The study is supported by funding from the German Research Foundation and the German Federal Ministry of Education and Research.A study reveals that two cavitation bubbles, generated in anti-phase with identical energy, can produce supersonic micro-jets. High-resolution simulations show that the jet amplification is driven by interactions between toroidal shock waves and bubble necking. The micro-jet reaches velocities exceeding 1000 m/s. The research demonstrates that potential flow approximations accurately predict the evolution of bubble gas-liquid interfaces. The study focuses on the dynamics of anti-phase bubble pairs with identical maximum radii. The second bubble is initiated when the first is at its maximum size, leading to fast jets with velocities up to 1400 m/s. The jet remains stable and penetrates the gas-liquid interface without atomizing. The experimental setup involves generating bubbles in deionized water using pulsed lasers. High-speed imaging and numerical simulations are used to analyze the bubble dynamics. The simulations use a high-order finite-volume method to solve the Navier-Stokes equations, capturing the interface between the bubble and liquid. The results show that the jet velocity reaches up to 3000 m/s immediately after ejection, reducing to 1200 m/s before impacting the second bubble. The jet remains at a reduced speed of 250 m/s after penetrating the second bubble. The supersonic velocity of the collapsing neck forms a conical shock wave inside the bubble, with a half-angle of 16 degrees, implying a jet velocity of about 3.6 times the speed of sound. The study identifies that the ultra-fast needle jet forms only in a narrow range of standoff distances (0.7 < γ < 0.8). Outside this range, the jet does not form due to insufficient energy focusing or unstable neck breakup. The mechanism involves the collapse of the elongated neck of the second bubble, leading to the emission of a shock wave that amplifies the jet velocity. The findings suggest that such supersonic jets could improve technical applications, such as needle-free injections. From a fundamental perspective, the mechanism offers a path to focus kinetic liquid energy through collective and resonant inertial cavitation bubble dynamics. The study is supported by funding from the German Research Foundation and the German Federal Ministry of Education and Research.