Quantum money is a theoretical form of currency that uses the physics of quantum mechanics to make counterfeiting physically impossible. Unlike traditional anti-counterfeiting measures (holograms, special inks, watermarks) that are merely difficult to copy, quantum money relies on a fundamental law of nature: quantum states cannot be duplicated. The idea has existed since the 1970s, and in 2025, researchers demonstrated a working version in the lab for the first time.
How Quantum Physics Prevents Counterfeiting
The core principle behind quantum money is something called the no-cloning theorem. In quantum physics, it is mathematically proven that you cannot make a perfect copy of an unknown quantum state. This isn’t a limitation of current technology. It’s a hard rule of the universe, like the speed of light.
Stephen Wiesner, a physicist, recognized this in the late 1960s and proposed embedding quantum information into banknotes. Each bill would contain a series of quantum bits (qubits), tiny particles of light or atoms prepared in specific orientations that only the issuing bank knows. A counterfeiter who intercepts a bill has no way to determine exactly how those qubits were prepared, and any attempt to measure them changes their state irreversibly. If a counterfeiter guesses the correct way to measure each qubit at random, their odds of successfully copying an entire bill drop to roughly 1 in 2 raised to the number of qubits. For a bill with even 20 qubits, that’s about a one-in-a-million chance. And it’s been proven that no strategy, no matter how sophisticated, can beat those odds.
Wiesner’s paper wasn’t published until 1983, over a decade after he wrote it, because the idea was so far ahead of existing technology. By then, Wiesner had left academia entirely and was working as a manual laborer. His concept became one of the founding ideas of quantum cryptography.
Private-Key vs. Public-Key Schemes
Wiesner’s original design is what researchers now call a private-key scheme. To verify a bill, you have to bring it back to the bank. The bank looks up the bill’s serial number, checks its records for how each qubit was originally prepared, and then measures each one in the correct way. If all the measurements match, the bill is genuine. This works, but it means the bank must be involved in every single transaction, which creates a bottleneck and potential security problems.
The more ambitious goal is public-key quantum money, where anyone can verify a bill’s authenticity without contacting the bank, but only the bank can create new bills. This would function more like physical cash: you accept it, check it yourself, and move on. Researchers have proposed mathematical frameworks for public-key quantum money, but building practical versions remains an open challenge. The difficulty lies in designing a verification process that anyone can perform without revealing enough information for someone to forge a copy.
How It Differs From Cryptocurrency
Quantum money and blockchain-based currencies like Bitcoin solve the counterfeiting problem in fundamentally different ways. Bitcoin prevents double-spending through a decentralized network of computers that collectively verify every transaction and record it on a public ledger. This requires enormous computational energy and introduces transaction delays.
Quantum money takes the opposite approach. Security lives in the physical object itself, not in a network. The laws of physics do the work that thousands of computers do for Bitcoin. One key difference in the trust model: blockchain systems allow untrusted participants (miners) to validate transactions, while quantum money assumes a trusted bank that mints the currency. Quantum money is also inherently centralized in its current formulations, since someone has to issue the quantum states in the first place.
The First Lab Demonstration
For decades, quantum money existed only on paper. That changed in September 2025, when a team at the Kastler Brossel Laboratory in Paris implemented Wiesner’s quantum money protocol in the lab. Published in Science Advances, the experiment used weak pulses of light with information encoded in their polarization. These pulses were stored in a quantum memory made from a large cloud of laser-cooled atoms, a platform that combines near-perfect efficiency with extremely low noise.
After storage, the quantum states were retrieved and run through the full verification protocol, passing strict security thresholds. The researchers called it the first time a quantum memory had been integrated into a complete cryptography protocol. It was a proof of concept, not a product, but it showed the physics works outside of theory.
The Storage Problem
The biggest practical barrier to quantum money is keeping quantum states alive long enough to be useful. Quantum information is extraordinarily fragile. Interactions with the surrounding environment cause qubits to lose their quantum properties, a process called decoherence. If your quantum banknote decoheres, it’s effectively destroyed, and your money is gone.
The best quantum memories today can hold a qubit’s state for about two hours, achieved in 2025 using ions in a cryogenic trap with sophisticated error correction. That’s a remarkable achievement in physics, but it’s obviously useless for money you’d want to keep in your wallet for days or years. Any real-world quantum money system would need quantum memories that last far longer, or a design where quantum states are generated and verified quickly rather than stored.
Infrastructure for Transferring Quantum Money
Even if the storage problem were solved, spending quantum money remotely would require a quantum network to transmit the quantum states from buyer to seller. In 2025, engineers at the University of Pennsylvania demonstrated that quantum signals can travel over ordinary commercial fiber-optic cable, the same cables that carry regular internet traffic. Their system used a small chip that coordinates quantum and classical signals, tested over about a kilometer of Verizon fiber in Philadelphia.
Scaling this beyond a single city is another matter. Quantum signals can’t be amplified the way regular light signals can, because amplification would require copying the quantum state, which the no-cloning theorem forbids. Long-distance quantum communication will eventually need quantum repeaters, devices that extend the range of quantum signals without copying them. These don’t yet exist in practical form. For now, quantum money transfers would be limited to short distances over fiber, or to in-person transactions where the physical token is handed over directly.
Where Quantum Money Stands Today
Quantum money is real physics but not yet real currency. The theoretical foundations are solid, with security guarantees rooted in the laws of quantum mechanics rather than computational difficulty. This makes it “unconditionally unforgeable,” a level of security that no classical anti-counterfeiting technology can claim. Classical security measures are always breakable in principle given enough computing power. Quantum money is not.
The financial sector is already preparing for the quantum era, though its focus is broader than quantum money specifically. The G7 Cyber Expert Group released guidance in 2024 urging financial institutions to begin migrating to quantum-resistant cryptography, and organizations like NIST, the Bank for International Settlements, and the European Quantum-Safe Financial Forum are developing standards and timelines. Many financial institutions have started pilot implementations of quantum-resistant encryption. Quantum money as a consumer product, though, remains years away, gated by advances in quantum memory duration, quantum networking, and the development of practical public-key verification schemes that don’t require a bank to authenticate every transaction.