158 research outputs found
An entanglement monotone derived from Grover's algorithm
This paper demonstrates that how well a state performs as an input to
Grover's search algorithm depends critically upon the entanglement present in
that state; the more entanglement, the less well the algorithm performs. More
precisely, suppose we take a pure state input, and prior to running the
algorithm apply local unitary operations to each qubit in order to maximize the
probability P_max that the search algorithm succeeds. We prove that, for pure
states, P_max is an entanglement monotone, in the sense that P_max can never be
decreased by local operations and classical communication.Comment: 7 page
Implementation of quantum search algorithm using classical Fourier optics
We report on an experiment on Grover's quantum search algorithm showing that
{\em classical waves} can search a -item database as efficiently as quantum
mechanics can. The transverse beam profile of a short laser pulse is processed
iteratively as the pulse bounces back and forth between two mirrors. We
directly observe the sought item being found in iterations, in
the form of a growing intensity peak on this profile. Although the lack of
quantum entanglement limits the {\em size} of our database, our results show
that entanglement is neither necessary for the algorithm itself, nor for its
efficiency.Comment: 4 pages, 3 figures; minor revisions plus extra referenc
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