Unforgeable quantum money tokens were the first invention of quantum information science, but remain technologically challenging as they require quantum memories and/or long-distance quantum communication.
More recently, virtual “S-money” tokens were introduced. These are generated by quantum cryptography, do not require quantum memories or long-distance quantum communication, and yet in principle guarantee many of the security advantages of quantum money.
Researchers have proposed implementations of S-money schemes with off-the-shelf quantum key distribution technology, and analyse security in the presence of noise, losses, and experimental imperfection.
Their schemes satisfy near-instant validation without cross-checking.
They showed that, given standard assumptions in mistrustful quantum cryptographic implementations, unforgeability and user privacy could be guaranteed with attainable refinements of our off-the-shelf setup.
Quantum tokens, also called quantum money, were invented by Wiesner in 1970.
npj Quantum Information, Published online: 11 March 2022; doi:10.1038/s41534-022-00524-4