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Quantum computers can search arbitrarily large databases by a single query

Lov K. Grover
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Abstract

This paper shows that a quantum mechanical algorithm that can query information relating to multiple items of the database, can search a database in a single query (a query is defined as any question to the database to which the database has to return a (YES/NO) answer). A classical algorithm will be limited to the information theoretic bound of at least O(log N) queries (which it would achieve by using a binary search).

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Lov K. Grover. 1997-08-12. Quantum computers can search arbitrarily large databases by a single query. https://doi.org/10.1103/physrevlett.79.4709

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