Google Revives Quantum Money, but the Technology Does Not Exist Yet

Researchers at Google working with collaborators in Texas and the Czech Republic have published a new theoretical study reviving quantum money, a decades-old idea for currency secured by physics rather than code.

If it ever worked, it could make a blockchain unnecessary for some purposes. A blockchain, the shared and constantly updated ledger behind Bitcoin, prevents counterfeiting through code and collective record keeping. The new proposal, called “Anonymous Quantum Tokens with Classical Verification,” would prevent counterfeiting through a rule of quantum physics known as the no-cloning theorem, which says an unknown quantum state can never be perfectly copied.

Unlike Bitcoin, though, the tokens would still come from a bank or another trusted central source. Dar Gilboa, a researcher involved in the study, stresses that the idea is centralized and not really “an analog of cryptocurrencies in any strong sense.”

For now, there is nothing to buy or spend. Gilboa says the work is theoretical and not a Bitcoin replacement. As Gilboa put it, “It assumes not only that you have a large, fault-tolerant quantum computer,” one that can correct its own errors at scale, “but also the ability to do quantum communication,” the ability to send quantum information over distances, “a whole other set of very difficult engineering challenges.”

Neither capability exists yet in the form the proposal would require. Gilboa called quantum technology “this crazy tool” and described the effort as “high risk, high reward.”