IBM achieves trusted quantum advantage with 70 qubits

IBM reported it encoded 70 logical qubits and ran a computation in roughly 15 minutes that the company says is beyond the reach of leading classical simulation methods. The experiment executed 2,415 logical two-qubit operations and 468 logical T gates. IBM said a new error-correction technique reduced logical error rates to about one-tenth of the underlying physical error rate.

Researchers at the University of Chicago collaborated on the work. IBM described the run as part of a push toward fault-tolerant quantum computing and said it used a structured verification method instead of random circuit sampling. The verification approach is designed to detect errors during the computation while preserving the mathematical difficulty that makes the problem hard for classical simulators. IBM said statistical checks support the accuracy of the result rather than relying solely on post-run comparisons.

Jay Gambetta, director of IBM Research and an IBM fellow, called the experiment “a new foundation for trusting quantum computers as they scale.” Bill Fefferman, an associate professor at the University of Chicago, said the techniques help characterize the fidelity of hard quantum states under noise and increase confidence that the machine is solving a computationally difficult problem.

IBM’s Starling roadmap sets a target of a large-scale fault-tolerant quantum computer by 2029 and calls for verified quantum advantage demonstrations before moving to modular processors and a system capable of roughly 200 logical qubits and around 100 million quantum operations. Over the past year IBM reported a 120-qubit GHZ cat state, introduced a 120-qubit Nighthawk processor and experimental chips to advance error correction, and expanded public access to more advanced quantum hardware.

On the issue of cryptocurrencies, IBM and outside researchers say the experiment does not materially change Bitcoin’s near-term security outlook. Bitcoin uses elliptic curve cryptography for digital signatures, and most estimates place the quantum resources needed to break those signatures at many thousands of fault-tolerant logical qubits, well above the 70 demonstrated here. Researchers and companies are developing post-quantum cryptographic upgrades and wallet designs aimed at resisting future quantum attacks without immediate changes to existing addresses.

IBM framed the demonstration as addressing two recurrent technical challenges in experimental quantum computing: lowering errors while scaling systems, and improving verification that devices perform the intended computation. The company said its error-correction approach lowered logical error rates and that the verification scheme helps detect errors in real time while keeping the problem difficult for classical simulation.