Classical search algorithm with resonances in $\sqrt{N}$ cycles
  In this work we use the wave equation to obtain a classical analog of the quantum search algorithm and we verify that the essence of search algorithms resides in the establishment of resonances between the initial and the serched states. In particular we show that, within a set of $N$ vibration modes, it is possible to excite the searched mode in a number of steps proportional to $\sqrt N$. 
A. Romanelli, R. Donangelo