Checks might not sound like a very high-tech option for sending money safely, but thanks to quantum computing, they may one day be forgery-proof. Researchers using IBM’s cloud-based quantum computer have run a proof of concept study on quantum currency and proxies like checks.
It would work like this: I owe you money, so I go to the bank and prove my identity. They issue me two qubits, both of which are linked to the remaining qubits that are still in the central computer at the bank. I give one of them to you, and after using my passcode to log into the system, I encode the qubit with the amount that I owe you. You can take that qubit to the bank. Since the bank can measure the state of any single qubit in an entangled system and identify the state of all qubits within that system, it can use this entanglement to verify that its own central computer was the origin of any given quantum check. Once it does that, it will give you the money.