Dmytro Gavisnky

The no-cloning theorem in quantum mechanics has been used as a basis for quantum money constructions, which guarantee unconditionally unforgeable currency. Existing schemes, however, either (i) require long-term quantum memory and quantum communication between the user and the bank in order to verify the validity of a bill or (ii) fail to protect user privacy due to the uniqueness of each bill issued by the bank, which can allow its usage to be tracked. We introduce a construction of single-use quantum money that gives users the ability to detect whether the issuing authority is tracking them, employing an auditing procedure for which we prove unconditional security. The use of our scheme does not require long-term quantum memory or quantum communication from the users themselves since their validation is a purely classical operation, making the protocol relatively practical to deploy. We discuss potential applications beyond money, including anonymous one-time pads and voting.