Quantum optical tristate Toffoli gate using frequency encoding principle of light with semiconductor optical amplifier

All-optical quantum logic gates with qubit data are the essential components in optical signal processing and computing. Quantum optical Toffoli gate is one of the most useful logic gates in the logic family which is extensively used to perform ultrafast optical digital operations. Here, in this paper, an all-optical scheme for realization of frequency encoded tristate Toffoli gate is proposed. Semiconductor optical amplifier based optical switches like frequency converters and add/drop multiplexers are used to implement the system. Also, a proper truth table and gate matrix of tristate Toffoli gate is developed. Tristate based optical logic operations not only increase the data handling capacity, it also increases the speed of different optical logic operations because of inherent parallelism of light. As frequency encoding principle is used to encode the qubits, so bit error problem can be ignored by the proposed system. The system is entirely all-optical in nature, so the system exhibits very high speed of operation (above tera hertz) with improved signal to noise ratio.