Quantum Money: The New Competitor for Blockchain By Google

The world of digital currencies has been built on the foundation of blockchain for over a decade. This complex system of distributed ledgers represents a revolutionary approach to digital scarcity and counterfeit prevention. However, researchers at Google are now exploring a solution that could completely bypass blockchain technology, where the security of currency stems not from code, but from the fundamental laws of physics.

The research into “quantum money” offers an alternative to cryptocurrencies such as Bitcoin and focuses on the problem blockchain aims to solve. If this approach proves successful—a significant prerequisite, as it presupposes advanced quantum computers—it could completely eliminate the need for blockchain's core technology and represent a fundamentally different path to a secure digital future.

In a recent study, titled “Anonymous Quantum Tokens with Classical Verification,” researchers from Google Quantum AI, the University of Texas at Austin, and the Czech Academy of Sciences have further developed a decades-old idea: a theoretical currency secured by the immutable laws of quantum mechanics. This research outlines a system in which money is not a single piece of data on a ledger, but a unique quantum object whose integrity is guaranteed by the fabric of reality itself.

The concept hinges on one of the strangest and most powerful principles in physics: the “no-cloning theorem.” This principle states that it’s impossible to make a perfect, independent copy of an unknown quantum state. While a set 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,” says Dar Gilboa, a researcher at Google Quantum AI and co-author of the study. “You can only succeed with a very small probability.” In this system, counterfeiting isn’t just computationally challenging, as with Bitcoin; it’s physically prohibited.

This highlights the potential of this technology as a direct threat to the blockchain model. The primary function of a blockchain is to prevent double spending without a central authority. This is achieved by creating a large, public, and immutable ledger—the distributed ledger—that is controlled by all participants. Quantum money solves the same problem much more directly. You don't need a global ledger to track ownership changes if the token itself is physically immutable and can only be spent once. Blockchain maintains the transactional history in a ledger, while quantum money secures the token itself.

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

Another Philosophy: The Centralized Compromise

While quantum currency has the potential to replace blockchain technology, it doesn't share the same decentralized philosophy. Gilboa emphasizes this distinction clearly: "We're not solving the same problem. What we're doing isn't decentralized, so it's not really an analogy with cryptocurrencies in a strong sense." Google's model assumes a trusted central issuer, such as a sofa, to create quantum tokens. Nevertheless, it makes ingenious use of physics to ensure fairness and integrity.

The system is designed to offer a strong privacy guarantee, preventing the bank from tracking its own currency. Users can collaborate to perform a "swap test" on their quantum tokens. "If they're not... identical, that means the bank could track you," Gilboa explains. Any attempt by the bank to secretly tag its funds would be immediately exposed.

This financial revolution won't happen tomorrow. Gilboa emphasizes that the research is entirely theoretical and far beyond current capabilities. "It assumes not only a large, fault-tolerant quantum computer, but also the possibility of quantum communication… a whole other set of very difficult technical challenges," he says. Nevertheless, the research is of great importance.

It demonstrates that the technology that has defined the last decade—the blockchain—isn't the only solution for securing digital assets. The brute-force accounting of a distributed ledger could one day be replaced by the elegant and absolute laws of the quantum realm. "It's this crazy tool," concludes Gilboa. "You can do all these wild things. It's high-risk, high-reward; but that's what makes it exciting."