Figure 2: An implementation of the Fredkin gate where feedbacks are eliminated.
From: All-optical design for inherently energy-conserving reversible gates and circuits
This design uses four coupling nodes. All nodes couple three channels. Three channels are used for nonlinear manipulation and denoted by F and F′. Each F is then manipulated with an appropriate nonlinear element denoted by γ, which transforms it to F′. The column index i represents different states.
