IBM and University of Chicago demonstrate verifiable quantum advantage The IBM quantum computer completed the 70-logical-qubit task in approximately 15 minutes, while leading classical simulation methods faced prohibitive runtimes IBM and researchers at the University of Chicago have completed a logical quantum computation that they say exceeded the practical reach of leading classical simulators while providing statistical evidence that the result was accurate. The experiment used 70 logical qubits to execute 2,415 logical two-qubit operations and 468 logical T gates. According to the researchers, the encoded computation achieved effective logical error rates 10 times lower than the system’s physical error rates. Their paper, Sampling hard circuits with verifiably high fidelity, sets out an approach designed to address a persistent problem in demonstrations of quantum advantage: how to verify a result once the computation has become too difficult for a classical computer to reproduce efficiently. Previous experiments have commonly used random circuit sampling, or RCS, which asks a quantum computer to generate complex patterns that classical systems cannot efficiently replicate. As the task becomes harder, however, independently checking the quantum computer’s answer also becomes increasingly difficult. The IBM and University of Chicago team instead developed a structured alternative to RCS. The researchers proved that it retained the same computational hardness criteria while allowing errors to be detected during the computation. “Verification remains one of the biggest challenges in firmly establishing experimental quantum advantage,” says Bill Fefferman, Associate Professor at the University of Chicago and a co-author of the paper. “This experiment develops techniques to better characterize the fidelity of hard quantum states under noise, increasing confidence that the quantum computer is solving a computationally hard problem.” Error correction supports 70 logical qubits Logical qubits encode quantum information in a way intended to shield it from errors affecting the underlying hardware. The