Craig Gidney Cuts Shor's Algorithm to 500,000 Qubits From 100 Million
Updated
Updated · New Scientist · Aug 25
Craig Gidney Cuts Shor's Algorithm to 500,000 Qubits From 100 Million
2 articles · Updated · New Scientist · Aug 25
Summary
500,000 qubits could be enough to run Shor’s algorithm, according to a March estimate by Craig Gidney and colleagues that slashed the previous requirement of more than 100 million.
That 200-fold reduction came from circuit optimization—making the factoring algorithm workable on smaller, more plausible quantum machines even though today’s largest systems still have only a little over 6,000 qubits.
Three months after the paper withheld some circuit details for safety, André Schrottenloher at Inria reconstructed most of them, underscoring how quickly the work is drawing follow-on research.
Quantum cybersecurity firms saw demand jump after the estimate, with one reporting a tenfold rise in business inquiries as companies weighed the risk of a future “Q-Day” that could break current encryption.
Gidney argues the work should accelerate migration to post-quantum cryptography rather than hasten catastrophe, as governments and businesses face a costly, slow transition to new standards.
If only 500,000 qubits can shatter modern encryption, what hidden breakthroughs might accelerate a quantum security collapse?
With adversaries already harvesting encrypted data, how many years remain before Q-Day exposes our deepest digital secrets?
Quantum Breakthroughs Slash Qubit Requirements: The 2026 Race to Crack RSA-2048 and ECC Threatens Global Cryptography
Overview
In 2026, quantum computing breakthroughs by Google and Iceberg Quantum showed that cracking major cryptographic standards like ECC and RSA now requires far fewer qubits than previously thought. Google’s optimized quantum circuits can break Bitcoin’s elliptic curve signatures in just nine minutes with under 500,000 qubits, making real-time blockchain attacks possible and prompting an accelerated shift to post-quantum cryptography. Meanwhile, Iceberg Quantum’s use of advanced QLDPC error-correcting codes slashed RSA-2048 requirements to under 100,000 qubits. These advances, combined with the permanent exposure of blockchain data and the growing 'Harvest Now, Decrypt Later' threat, have made immediate migration to quantum-resistant standards urgent for organizations worldwide.