How One Shutter Can Close N Slits
  It is shown that a quantum shutter, pre- and post-selected in particular quantum states, can close simultaneously arbitrary number of slits preventing the passage of a single photon in an arbitrary state. A set of K pre- and post-selected shutters can close the slits preventing the passage of K or less photons. This result indicates that the surprising properties of pre- and post-selected quantum systems are even more robust than previously expected. 
Y. Aharonov and L. Vaidman