Consensus Is the Last Middleman: The Case for Quantum Money

Quantum computers could one day break Bitcoin (BTC), yet the same physics could also build money that is impossible to forge. Two experts argue that quantum money, not the blockchain, may be the final form of digital cash.

Stefano Gogioso and Daniela Herrmann made the argument during the latest BeInCrypto Experts Council. Their case rests on an idea older than crypto itself, and on a single law of physics.

Money Has Always Been a Story About Trust

A companion analysis asked when quantum computers might break Bitcoin. This piece asks the opposite question. What if the same technology builds something better than the money we use today?

The answer begins with a line from Gogioso that reframes the debate. Consensus, he says, is “the last middleman.”

To see why, it helps to trace how money lost its trust in the first place.

Physical cash needs no middleman. A gold coin proves itself, and a buyer does not have to trust a bank, a ledger, or a network to accept it. Cash, however, cannot travel down a wire.

Digital money solved distance, but it brought the middlemen back. Every online payment now trusts an intermediary to confirm that the same unit is not spent twice.

Bitcoin answered that problem by replacing institutions with math and consensus. Thousands of computers agree on one shared history, so no central party is needed.

The idea of using physics instead of trust, however, is older than Bitcoin. It is older than the modern internet.

In the late 1960s, a Columbia University graduate student named Stephen Wiesner wrote a manuscript called “Conjugate Coding.” Journals rejected it, and it stayed unpublished until 1983.

Wiesner proposed money that could not be counterfeited, protected by physics rather than by a bank. It was the first real use anyone had imagined for quantum information.

That work later inspired the 1984 protocol known as BB84, which launched quantum cryptography. In effect, the whole field grew out of an attempt to make unforgeable money.

Security From Physics, Not Secrecy

Classical cryptography rests on hard math problems. A code stays safe because solving it would take too long. Quantum cryptography works on a different footing.

Its guarantee comes from a physical law called the no-cloning theorem. Physicists William Wootters and Wojciech Zurek proved it in 1982. An unknown quantum state cannot be perfectly copied.

The mechanism is elegant. Any attempt to copy the state disturbs it. The forgery fails, and the tampering shows.

Gogioso has spent years turning that law into working tools. At an earlier BeInCrypto interview in Naples, he described keys that defend themselves. If someone intercepts a quantum key, it is destroyed in transit, and the receiver sees the protocol break.

On the Council panel, he pushed the idea to its limit.

“You can build applications that do not need to trust the very hardware they run on. You can literally commission the hardware from your attacker, and as long as the application passes its self-testing, you are guaranteed security. Worst case, it simply refuses to run. And this is provably impossible classically.”

Specialists call this device-independent cryptography. The security holds even if the manufacturer is hostile. That property matters because complex hardware is exactly where backdoors tend to hide.

Why Unforgeable Keys Become Money

The step from security to money is short. Cheating and forgery are the same problem in different words.

If you cannot copy a quantum state, you cannot counterfeit it. And a thing that cannot be counterfeited can serve as money.

Gogioso drew the line directly.

“A different way of saying you cannot cheat is saying you cannot copy or forge. From the very same family of techniques, you get quantum money, or quantum financial instruments. New ways of doing digital finance with far fewer trust assumptions on intermediaries, networks, and counterparties.”

His team has already built the smallest version of the concept. In Naples, he demonstrated keys that work only once. To spend one, you have to destroy it, which stops an attacker from replaying an old payment.

A single-use key is a tiny piece of unforgeable value. Scale that principle up, and you reach what researchers call quantum money.

The theory is not new. In 2012, Scott Aaronson and Paul Christiano proposed the first public-key quantum money scheme. It lets anyone verify a note, not only the bank that issued it. Their framing echoed Wiesner almost exactly, describing money that cannot be counterfeited according to the laws of physics.

Quantum Money and the Last Middleman

Now the pieces meet. Bitcoin removed the banks, but it did not remove trust. It shifted that trust onto a network and a shared ledger. Something still has to agree on which payments are real.

Gogioso views that agreement as the final intermediary. Web3 and zero-knowledge tools clawed back some of the trust that digital money gave away, he says, yet consensus still does the last job of preventing forgery.

That job carries a cost. Consensus demands coordination, energy, and a crowd of participants who must broadly agree. A physical guarantee needs none of those things.

Quantum money, in his telling, removes the middleman completely.

“Quantum money is the next and final evolution of that story. You recover something digital that you can transact at a distance, but without trusting intermediaries, global ledgers, or someone deciding which transactions go into an Ethereum (ETH) block. The physics gives you the unforgeability directly. In that sense, consensus is truly the last middleman.”

The claim is large, so it is worth stating plainly. If it holds, quantum money would be to Bitcoin what Bitcoin was to the bank.

There is a symmetry worth noting. The physics that threatens Bitcoin’s signatures is the same physics that could retire the need for consensus altogether.

The One Defense That Survives Smarter Attackers

There is a further reason the timing matters. Artificial intelligence is getting better at breaking things.

Most security today assumes the attacker is not clever enough, or that a problem is simply too hard to solve in time. Gogioso argues that this assumption looks fragile in an age of capable AI.

Physics offers a different kind of promise.

“What quantum really buys you is security based on the laws of the universe. It doesn’t matter how smart the AI is. You can’t break it. Worst case, you can stop it from happening, but you cannot forge it.”

That is the deeper appeal of the approach. A quantum guarantee does not depend on the attacker’s limits. It depends on the structure of reality, which no amount of intelligence can rewrite.

Quantum Money: Not Here Yet, but Within Reach

Both guests were careful not to oversell the idea. Herrmann, whose firm builds commercial quantum tools, marked the boundary clearly.

“Quantum money is the vision, once this all plays out. Right now, quantum money as such isn’t available yet. But as soon as the chips advance, these things have to be handled with real responsibility.”

The main obstacle is quantum memory. Holding a fragile quantum state is difficult, and today the best systems keep one for only seconds. Gogioso has said that the limit still puts full quantum money out of reach, though the same hardware already suits short-lived tasks.

Even so, the direction is set. Laboratory experiments have begun to demonstrate quantum tokens and related schemes, moving the idea off the page.

Gogioso closed the panel on that note.

“Within five, six, seven years we could live in a world where we use quantum resources to do things that are provably impossible today. Not just hard, not just slow, actually impossible. And this is software we can start building today, not in five years. The future is absolutely within reach.”

More than half a century after Wiesner sketched money that physics itself would guard, the idea is finally leaving the whiteboard. If Gogioso and Herrmann are right, the last middleman may not survive the decade.

The post Consensus Is the Last Middleman: The Case for Quantum Money appeared first on BeInCrypto.

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