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An adaptive attack on Wiesner's quantum money
Unlike classical money, which is hard to forge for practical reasons (e.g. producing paper with a certain property), quantum money is attractive because its security might be based on the no-cloning theorem. The first quantum money scheme was introduced by Wiesner circa 1970. Although more sophisticated quantum money schemes were proposed, Wiesner’s scheme remained appealing because it is both conceptually clean and relatively easy to implement.
We show an efficient adaptive attack on Wiesner’s quantum money scheme [Wie83] (and its variant by Bennett et al. [BBBW83]), when valid money is accepted and passed on, while invalid money is destroyed. Our approach is based on interaction-free measurement and the quantum Zeno effect, also known as Elitzur-Vaidman’s bomb tester. It allows us to break Wiesner’s scheme with 4 possible states per qubit, as well as against generalizations which use more than 4 states per qubit.
Joint work with Daniel Nagaj