Google’s Quantum Money Is Not Crypto, Because It Needs a Bank
The tokens would be physically impossible to copy, but they still have to be issued by someone users trust.
Decrypt · Physics vs. Code: Why Google’s ‘Quantum Money’ Could Make Blockchain ObsoleteDar Gilboa, a researcher with Google Quantum AI and a co-author of a new study on money secured by physics instead of code, made the point directly. His team’s idea for quantum money, he said, should not be mistaken for another cryptocurrency.
“We’re not solving the same problem,” he said. “What we’re doing isn’t decentralized, so it’s not really an analog of cryptocurrencies in any strong sense.”
Gilboa also cautioned that the proposal remains on paper and cannot be built with today’s machines. It would need dependable quantum computers far more powerful than what exists, plus networks that can transmit quantum states, work he described as very difficult.
What Gilboa means starts with a dollar bill. “If you had a $1 bill that was actually a quantum state, you could prove, based on the properties of quantum mechanics, that copying such a state is impossible,” he said. “You could only succeed with very small probability.” Ordinary computer files can be duplicated endlessly, but an unknown quantum state cannot be perfectly copied.
That distinction, in his argument, changes what money needs. In Bitcoin, counterfeiting is merely computationally difficult. Thieves are kept out because rewriting the record is too expensive and too hard. Under quantum money, counterfeiting would be physically forbidden.
It is also why Gilboa believes the blockchain itself could become redundant. A blockchain exists mainly to stop double spending without a central authority, by keeping one giant shared record of who spent what that everyone can see. If each token is physically uncopyable and can be spent only once, he argues, you do not need that global ledger or the energy intensive work that secures it. Checking a payment would mean testing the token itself rather than asking a whole network to agree.
The model departs from crypto’s decentralized idea because it still requires a trusted central issuer, like a bank, to create the quantum tokens.
Questions people ask
Why would uncopyable money not need a blockchain?
Because the token itself cannot be copied, the same money cannot be spent twice. A blockchain stops double spending by keeping a shared public record that everyone checks. Quantum money would solve that problem in the object, so there would be nothing to check against.
Who makes quantum money, if not miners?
A central issuer such as a bank creates the quantum tokens. That issuer is necessary because someone has to make the special quantum states in the first place. The difference from ordinary bank money is that physics would then limit what even the issuer can do.