Beam-me-up money

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In Star Trek, it took only seconds to travel from the Starship Enterprise down to a nearby planet.

Crewmembers only had to step into the Transporter, which dematerialized them into a pattern of energy (accurate to the quantum level) and beamed them to a target location where the energy would be converted back into matter so the person could be reassembled.

But is the person who beams back up the same that beamed down?

The official, in-universe answer is that they’re one and the same. The consciousness of transported crewmembers remains continuous, they say, thanks to the perfection of the Transporter’s quantum-level scan and reconstruction.

As proof, they cite crewmembers claiming a memory of being in transit.

But we’ve since learned how quantum-level transportation works, and that’s not it.

In quantum teleportation, first discovered in 1993, the only thing being teleported is information.

Teleporting, say, a qubit, requires that the original quantum state of that qubit be destroyed: By the laws of physics, collecting precise information on a quantum state collapses its superposition, thereby destroying it.

But the collected information can then be sent as classical data (ones and zeros) over a satellite or fiber optic cable and then, thanks to the physics-magic of entanglement, reassembled (from other particles) at its destination.

So the unsettling truth is that the Transporter on the Starship Enterprise can only have worked by killing its passengers — the crewmember who beamed down is not the one who beamed back up.

This has some sci-fi implications for the future of money.

In banking, the way money is “sent” from Bank A to Bank B is that Bank A subtracts a number in its spreadsheet and sends a message to Bank B instructing it to add the same number to theirs.

Only the message is sent, not the money — which is why we need banks: to send each other messages about our money.

With quantum money, however, the money sends its own messages.

Quantum money is the idea that value could be represented by the quantum state of a particle and exchanged via quantum teleportation.

“The most important thing to understand here is that quantum [money] behaves like a resource, not like data,” Fabrizio Genovese explained in an email.

Where a bank deposit is information about money and Bitcoin is a consensus record representing money, quantum money would be the money itself — an uncopyable atom, photon, or molecule that is money.

Not data about money but the physical resource of money.

This has utility because it would allow money to be secured and transported according to the unbreakable laws of superposition, entanglement and the no-cloning theorem.

In other words, physics might someday do what databases and distributed ledgers do now, but without the database or distributed ledger.

Quantum money would therefore have the self-custodial properties of physical cash: You could keep qubits of money in a hardware device the same way you keep cash in your pocket.

That would make exchanging money perfectly permissionless (no intermediary required) and perfectly private (there’s no ledger of transactions).

But quantum money would also have the transportable properties of digital money: Destroying the money on your device creates the sendable information required to recreate it on another device, however far away.

(There is a moment when the quantum state, in transit as classical data, does not exist — which proves that the Star Trek Transporter really is a suicide machine.)

Sending quantum money will be like sending physical cash in the mail. But better, because it arrives instantly.

Sending money over great distances created the need for banks, but solving that problem introduced the intermediaries that now control nearly all of our money.

Bitcoin, of course, is a way of making peer-to-peer transactions possible over great distances.

But quantum money would be the unstoppable way to do it.

“Blockchain transactions are not quite peer-to-peer,” Stefano Gogioso says, “because there’s always going to be part of the mechanism that can stop your transaction from going through. For economical, political, or technological reasons.”

Nothing will stop a quantum transaction, for any reason.

There is one limitation, however: Unlike Star Trek, where Captain Kirk could beam down to a newly discovered planet, quantum money can only be transported to a hardware device prepared to receive it.

That device does not yet exist, so quantum money is not yet feasible — we’re three or four years away from the earliest iteration, Gogioso estimates.

When it arrives, though, it will be the safest conceivable way to send money.

Getting security from quantum states, Genovese says, is like getting energy from the Sun: “It’s what the universe gave us.”

As such, he expects all cybersecurity will eventually be done through quantum states — including money.

We’ll still have to give that money value, however, which might prove to be the hardest trick.

Building a transporter to teleport qubits is one thing; getting others to accept them as payment is another.