Reading · In the future, everyone will be famous for 15Mb

Dateline: London, 16th July 2026.

When Bitcoin goes the way of Spanish doubloons, what comes next? Some of the ideas floating around might sound fantastical, but they really aren’t. Or at least, they aren’t more fantastical than quantum mechanics, which may well play a part.

I was thinking about this because I happened to be listening to the “Bits + Bips” podcast recently and enjoyed an interesting discussion about the future of money. During the discussion, this comment on the future of money stood out for me:

“We’re going to have quantum money. You’re going to see some successor to Bitcoin that’s quantum encryption resistant. That’ll be the next move. It won’t be in the next few years, but that’s what you want to keep an eye on. There’s going to be some flurry of quantum money coins that are created in a few years’ time.”

This sounds a little fantastic, but it really isn’t. That mention of “quantum money coins” caught my attention precisely because it is entirely possible to use quantum mechanics to create electronic cash using the physical properties of nature. I’ve written about this before, so let me just quickly summarise here why there is a future quantum option for digital currency.

It is all to do with the “double-spending problem” that is fundamental to the world of digital assets. If I send you a picture of my cat, I am sending you a copy. I still have the original and I can send another copy to someone else. That is fine for pictures of cats, but not so good for money. If I send you a digital dollar, then I should not be able to send a copy of that dollar to someone else! So we want to transfer data representing value (i.e., tokens) from one owner to another so that ownership is easy to determine and unequivocal. There are essentially four ways to do this.

First, you could simply have a giant database that lists all the tokens and records which ones have been spent so that you can’t spend them twice. That is an undeniably cheap and simple way but it does create something of a single point of failure. This is actually how David Chaum’s innovative “eCash“ system worked way back in the 1980s.

Secondly, you could store the tokens in some form of secure hardware. You can copy software but you cannot copy hardware. This is why mobile phone SIMs and chip and PIN cards work. This is actually how NatWest bank’s “Mondex” digital currency system worked back in the 1990s (the reason we celebrate July 4th in England).

Third, and this is how cryptocurrency works, you could implement the tokens in software using some form of clever consensus mechanism to ensure that the right tokens are attributed to the right owners and cannot be misappropriated by bad actors. (Mr. Satoshi’s great breakthrough was to find a way to align the economic incentives around forming a secure consensus with the work required to do so.)

Finally, and this may well happen in the future, you could use the basic principles of quantum mechanics to create electronic cash exploiting the physical properties of nature. The Swedish central bank published an interesting paper about this a couple of years ago which, while noting that any such implementation might be some way off, pointed out that this could be a very good way to transmit electronic cash instantaneously across the universe. This kind of quantum money exploits the fact that it is not possible to clone an unknown quantum state. This means that a counterfeiter, even with access to unlimited resources, will still not be able to copy a quantum coin.

(Why their research paper wasn’t called “Schrödinger’s Cash” I’ll never know, but I guess they’re not marketing people.)

It’s probably best no to think too much about quantum mechanics, but if you want to you can think of this quantum cash as banknotes whose secret security features are holograms but quantum systems (like photons) prepared in special, hidden configurations. The magic defence against unlimited resources is the “no‑cloning theorem”. That is, if you do not know the exact quantum state, physics prevents you from making an identical copy. If a counterfeiter tries to “look” at the quantum pattern to copy it, the act of measuring disturbs it and changes it, so the copy will almost surely fail the bank’s later check. With enough quantum systems on each note, the chance of a forged note passing verification becomes astronomically small.

In case you are interested in exploring these possibilities in more detail, see my paper “Clouds, chips or chains? The three ways to implement a digital dollar: FedPesa, FedDex or FedCoin” in the Journal of Payments Strategy and Systems 14(4):339–52 (2020). And if you a wondering why I only list three ways, it’s because I thought that back in 2020 it might be difficult to persuade a bank to spend R&D money on quantum banknotes.

This is why tokens (and the world of decentralised finance in general) are so interesting: At the basic level, tokens are data that cannot be double spent. You can transfer them but you cannot copy them. When I send you a token, whether a coin or a link to a picture of a chimpanzee with sunglasses on or a digital dollar or a claim to a barrel of oil or whatever, then you have the token and I do not. I cannot then send a copy to someone else. That makes for a very low-cost infrastructure for transactions, which is precisely why organisations ranging from JP Morgan to Stripe are interested in it.

So, we can solve the double-spending problem in many different ways. But where might that take us? In the podcast I mentioned earlier, Austin Campbell, Ram Ahluwalia and Chris Perkins go on to talk more generally about what might come after Bitcoin. This is a subject that fascinates me, and not only because I wrote a book about it (it’s called “Before Babylon, Beyond Bitcoin”, by the way) but also because over the years I have taken part in numerous discussions, panels and workshops on the topic.

Anyway, during that discussion, Ram says “It’s going to be wrapped energy, wrapped compute”.

Interesting. And I can’t help but refer back here to the work of the artist Austin Houldsworth. His piece “Electric Money” (2008) imagined a future where digital currency had been hacked and a new system was implemented using kWh as ‘currency’. As I said in the context of the Future of Money Design Award, that was surprising a couple of decade back but now in a world of data centres in space and resource rapacious AI, it seems almost inevitable!

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Bitcoin is not that good as a payment system, which is why initiatives such as Tempo exist. It is also not very flexible for anything beyond simple value transfer. Compared with newer distributed ledger systems, it has limited native support for rich programmability, identity or complex financial workflows.

So, if Bitcoin turns out to be the Compuserve of currency, then what will be the Internet? When the podcast pals went on to observe that “the best digital asset might not yet exist” I have to say that I fundamentally agree with this (to me at least) obvious point. It sounds radical to say that the future is about trading electricity or compute (or oil or water or Taylor Swift tickets or the right to reside in Singapore) rather than currency, but it really isn’t. It’s a point that’s been made before, and I am not the only one to think this, but if you can trade digital assets 24/7 in liquid markets, why would you ever “cash out” of those assets into currency?

The Next Bitcoin

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