Physics versus code: why Google’s ‘quantum money’ could make blockchain obsolete

For more than a decade, the world of digital currency has been based on a single foundation: blockchain.

This complex, code-based system of distributed ledgers was a revolutionary approach to creating digital scarcity and preventing counterfeiting.

But now Google researchers are exploring a concept that could circumvent it altogether, securing money not by a string of code but by the fundamental laws of physics.

This new research into “quantum currency” offers an alternative to cryptocurrencies like Bitcoin and targets precisely the problem a blockchain was designed to solve.

If successful – a big if, as it involves advanced quantum computers – it would effectively eliminate the need for core blockchain technology, representing a fundamentally different path to a secure digital future.

In a new study, called “Anonymous quantum tokens with classical verification,“ Researchers from Google Quantum AI, the University of Texas at Austin, and the Czech Academy of Sciences have advanced a decades-old idea: a theoretical currency secured by the unalterable laws of quantum mechanics.

The article describes a system in which money is not just a piece of data written in a ledger, but a unique quantum object whose integrity is guaranteed by the fabric of reality itself.

The uncopyable dollar

The concept is based on one of the strangest and most powerful principles in physics: the “no-cloning theorem.”

This law states that it is impossible to create a perfect, independent copy of an unknown quantum state. While a string of data on a computer can be copied infinitely, a quantum state cannot.

“If you had a dollar bill that was actually a quantum state, you could prove, based on the properties of quantum mechanics, that copying such a state is impossible,” said Dar Gilboa, a quantum AI researcher at Google and co-author of the study. Decrypt. “You can only succeed with a very low probability.”

In this system, counterfeiting is not only computationally difficult, as in the case of Bitcoin; it is physically prohibited.

Replace the ledger with physics

This is where the technology becomes a direct threat to the blockchain model.

The main function of a blockchain is to prevent “double spending” without a central authority. It does this by creating a massive, public, immutable ledger – the distributed ledger – that everyone looks at.

Quantum money solves the same problem in a much more direct way. You don’t need a global ledger to track ownership history if the token himself is physically uncopyable and can only be spent once.

• Blockchain secures transaction history in a ledger.
• Quantum Money secures the token itself.

If each digital dollar has its own inherent physical security, the entire energy-intensive apparatus of a proof-of-work blockchain becomes redundant. Verification is a direct physical process and not a global consensus event.

A different philosophy: centralized compromise

While quantum money could replace blockchain technology, it does not share its decentralized philosophy. Gilboa is quick to make this distinction.

“We are not solving the same problem,” he stressed. “What we’re doing is not decentralized, so it’s not really an analogue of cryptocurrencies in the strict sense.”

Google’s model assumes that a trusted central issuer, such as a bank, creates quantum tokens. However, he uses physics brilliantly to keep this problem honest.

The system is designed to provide a powerful privacy guarantee, preventing the bank from tracking its own currency. Users can team up to perform a “test swap” on their quantum tokens.

“If they’re not…identical, that means the bank might be tracking you,” Gilboa said. Any attempt by the bank to secretly mark its money would be immediately exposed.

A glimpse of a distant future

This financial revolution will not happen tomorrow.

Gilboa emphasizes that the research is entirely theoretical and far beyond current capabilities.

“That requires not only that you have a large, fault-tolerant quantum computer, but also the ability to do quantum communications…a whole other set of very difficult engineering challenges,” he said.

Despite this, research is extremely important.

This shows that the defining technology solution of the last decade – blockchain – is not the only answer to securing digital value. The brute force accounting of a distributed ledger may one day be replaced by the elegant and absolute laws of the quantum realm.

“It’s a crazy tool,” Gilboa concluded. “You get to do all these crazy things. It’s high risk, high reward, but that’s what makes it exciting.”