Quantum Money

Eh? A Monday morning something I at least knew nothing about...

The challenge is to create a quantum state that can work as a form of money. Just like ordinary cash, quantum cash would be exchanged in lieu of goods. It would be sent and received over the internet without the need to involve third party parties such as banks and credit card companies. That would make transactions anonymous and difficult to trace, unlike today's online transactions which always leave an electronic paper trail. That's one big advantage over today's money.

Another is that quantum states cannot be copied so quantum cash cannot be forged.

But quantum cash must have another property: anybody needs to be able to check that the money is authentic. That turns out to be hard because measurements on quantum states tend to destroy them. It's like testing classical bills by seeing whether they burn.

But there is a way round this based on the ideas behind public-key encryption....

More.