Comment on quant-ph/0506105: The modified Grover algorithm cannot   speedup unsorted database search
  In a recent paper (quant-ph/0506105), A S Gupta, M. Gupta and A. Pathak proposed a modified Grover algorithm that would exponentially accelerate the unsorted database search problem if the number of marked items is known. If this were true, it would represent a major fundamental breakthrough in computer science, mathematics, quantum information and other related branches of sciences.   However the algorithm is not valid. We will explain it in this brief comment. 
Gui Lu Long