Multi-object searching algorithm using subgrouped oracles
  We present in this work, if a set of well organized suboracles is available, an algorithm for multiobject search with certainty in an unsorted database of $N$ items. Depending on the number of the objects, the technique of phase tunning is included in the algorithm. If one single object is to be searched, this algorithm performs a factor of two improvement over the best algorithm for a classical sorted database. While if the number of the objects is larger than one, the algorithm requires slightly less than $\log_{4}N$ queries, but no classical counterpart exists since the resulting state is a superposition of the marked states. 
Jin-Yuan Hsieh, Che-Ming Li, and Der-San Chuu