Quantum search algorithm as an open system

We analyze the responses of a quantum search algorithm to an external monochromatic field and to the decoherences introduced through measurement processes. The external field in general affects the functioning of the search algorithm. However, depending on the values of the field parameters, there are zones where the algorithm continues to work with good efficiency. The effect of repeated measurements can be treated analytically and, in general, does not lead to drastic changes in the efficiency of the search algorithm.