Stefano Gogioso, a quantum computing lecturer at the University of Oxford and co-founder of quantum security firm Spooqy, published on June 17 a paper outlining the technical specifications for a quantum memory device that would make quantum money viable. The device does not yet exist: the best laboratory systems can maintain a quantum state for only seconds, while Gogioso’s design requires stability measured in months, portability from shipping containers to pockets, and capacity for billions of distinct states. Gogioso’s argument establishes that a fault-tolerant quantum computer necessarily implies quantum memory, and that a machine with 500,000 physical qubits would suffice to break Bitcoin’s signatures, according to a study published in March by Google Quantum AI with the Ethereum Foundation and Stanford University. The same hardware development would power quantum money, making it impossible for Bitcoin to be vulnerable without an alternative already being feasible.
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