‘The universe never did make sense; I suspect it was built on government contract.’ — Robert A. Heinlein
A new scheme for making quantum money could lead to cash that cannot be counterfeited. But it may also lead to a new breed of quantum crime.
In the last couple of years, a number of quantum dignitaries have become interested in the (relatively) ancient problem of quantum money.
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.
