- The authors performed a loophole-free Bell test experiment using superconducting circuits to violate Bell's inequality. They entangled pairs of qubits over a 30 meter distance and measured them in randomly chosen bases, accumulating over 1 million trials. - The average S value obtained was 2.0747 ± 0.0033, violating Bell's inequality with a p-value smaller than 10-108, demonstrating non-local quantum correlations between the spatially separated qubits. This establishes superconducting circuits as a viable platform for foundational tests of quantum physics and applications in quantum information.