From orthogonal projections to a generalized quantum search

From orthogonal projections to a generalized quantum search A quantum algorithm with certainty is introduced in order to find a marked pre-image of an element which is known to be in the image domain of an orthogonal projection operator. The analysis of our algorithm is made by using properties of the Moebius transformations acting on the complex projective line. This new algorithm closely resembles the quantum amplitude amplification algorithm, however it is proven that our algorithm is a proper generalization of the latter (with generalized phases), in such a way that the quantum search engine of the main operator of quantum amplification is included as a particular case. In order to show that there exist search problems that can be solved by our proposal but cannot be by applying the quantum amplitude amplification algorithm, we modify our algorithm as a cryptographic authentification protocol. This protocol results to be robust enough against attacks based on the quantum amplitude amplification algorithm. As a byproduct, we show a condition where it is impossible to find exactly a pre-image of an orthoghonal projection. This result generalizes the fact that, it is impossible to find a target state exactly by using quantum amplification on a three dimensional invariant subspace. Quantum Information Processing Springer Journals

From orthogonal projections to a generalized quantum search

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Springer US
Copyright © 2012 by Springer Science+Business Media, LLC
Physics; Quantum Information Technology, Spintronics; Quantum Computing; Data Structures, Cryptology and Information Theory; Quantum Physics; Mathematical Physics
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