Zero-knowledge convincing protocol on quantum bit is impossible
Pawel Horodecki, Michal Horodecki, Ryszard Horodecki · Quantum · 2017
Consider two parties: Alice and Bob and suppose that Bob is given a qubit system in a quantum state ϕ , unknown to him. Alice knows ϕ and she is supposed to convince Bob that she knows ϕ sending some test message. Is it possible for her to convince Bob providing him "zero knowledge" i. e. no information about ϕ he has? We prove that there is no "zero knowledge" protocol of that kind. In fact it turns out that basing on Alice message, Bob (or third party - Eve - who can intercept the message) can synthetize a copy of the unknown qubit state ϕ with nonzero probability. This "no-go" result puts general constrains on information processing where information about quantum state is involved.