Privacy and Interaction in Quantum Communication Complexity and a Theorem about the Relative Entropy of Quantum States
نویسندگان
چکیده
We prove a theorem about the relative entropy of quantum states, which roughly states that if the relative entropy, S(ρ‖σ) ∆ = Tr ρ(log ρ− log σ), of two quantum states ρ and σ is at most c, then ρ/2 ‘sits inside’ σ. Using this ‘substate’ theorem, we give tight lower bounds for the privacy loss of bounded error quantum communication protocols for the index function problem. We also give tight lower bounds for the k-round bounded error quantum communication complexity of the pointer chasing chasing problem, when the wrong player starts, and all the log n bits of the kth pointer are desired.
منابع مشابه
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