Scaling of multiple postselected quantum gates in optics
Timothy C. Ralph · Physical Review A · 2004
We show that interesting multigate circuits can be constructed using a postselected controlled-sign gate that works with a probability ${(1∕3)}^{n}$, where $n\ensuremath{-}1$ is the number of controlled-sign gates in the circuit, rather than ${(1∕9)}^{n\ensuremath{-}1}$, as would be expected from a sequence of such gates. We suggest some quantum information tasks which could be demonstrated using these circuits, such as parity checking and cluster-state computation.