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Implementation of quantum search algorithm using classical Fourier optics

N. Bhattacharya·H. B. van Linden van den Heuvell·R. J. C. Spreeuw
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Abstract

We report on an experiment on Grover's quantum search algorithm showing that {\em classical waves} can search a $N$-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 $\sim\sqrt{N}$ 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.

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N. Bhattacharya, H. B. van Linden van den Heuvell, R. J. C. Spreeuw. 2002-02-01. Implementation of quantum search algorithm using classical Fourier optics. https://doi.org/10.1103/physrevlett.88.137901

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