ETH Zurich physicists have demonstrated a way to turn imperfect random inputs into random bits certified by a quantum experiment. The team connected two superconducting quantum chips through a 30-metre refrigerated link and combined a loophole-free Bell test with a randomness-extraction algorithm. The result addresses a weakness in cryptography: apparently random inputs can contain correlations that make secret keys predictable.
The experiment demonstrates randomness amplification, a task that cannot be achieved using classical processing alone under the same assumptions. Its certification comes from the measured quantum correlations rather than trust in the devices' internal construction. The present apparatus requires cryogenic hardware and a long physical separation between the chips; turning the result into a practical randomness service remains a further engineering step.
