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The quantum Toffoli gate is one of the essential reversible universal logic gates widely used for optical data processing. Herein, a new scheme of developing all‐optical Toffoli gate using a two‐dimensional silicon–air photonic crystal is proposed. For the realization of the Toffoli gate, the principles of constructive and destructive interference of light are used. The Toffoli gate comprises two‐input–three‐output‐based optical AND gate, and a two‐input–one‐output optical XOR gate. Two Y junction power splitters have been used at the two inputs of the AND gate. The operating wavelength of the proposed Toffoli gate is 1550 nm along with the wafer size of 50 µm × 50 µm. The performance of the Toffoli gate has been analysed and simulated by the plane‐wave expansion method and finite‐difference time‐domain method. The response time and contrast ratios are also obtained from the simulation. The proposed Toffoli gate is intensity encoded with no non‐linear material within the crystal which shows significant improvement over other proposals. [ABSTRACT FROM AUTHOR]

• All optical 3-qubit Fredkin gate with Photonic Band gap Crystal. • A small structure is used for the proposed system of dimension 60 µm × 75 µm wafer. • This structure has a response time of 3.5 ps. • All-optical combinational/ sequential systems can be realized from the implemented system. The authors demonstrate an all-optical Fredkin gate which implements an interference based controlled swap operation. This realization has a small footprint (60 µm × 75 µm wafer size), and in this scheme, the phase shifts are achieved by the variation of the path length of the light necessary for the operation. For the simulation, the wavelength used is 1550 nm. This reversible logic gate optimizes the power requirement and have a non-dissipative operation. PWE and FDTD methods are used for the simulation process. The novelty of the proposed research work is that the implementation of the Fredkin gate is organized only by the constructive/destructive interferences of the light. No nonlinear switching is used to do it and hence the speed of operation goes faster than most of the the Fredkin gates in PhCs using non linearities and it proposes a very good contrast ratio. [ABSTRACT FROM AUTHOR]

• All-optical integrated Pauli X, Y and Z gate system is proposed. • The system implemented with a photonic bandgap crystal made of Si-air configuration. • The implementation is a linear system operating at 1550 nm wavelength. • Response time is 2 ps, contrast ratio of 10.4 dB and bit rate of 0.25 Tbps. • The smaller footprint of 70 µm × 70 µm. • The proposed device can help build a photonic chip in the nanodomain. Nano-scale all-optical logic gates systems are desirable for the all-optical computing and signal processing applications. All-optical Quantum computing offers excellent computational abilities and lossless operations. The Pauli X, Y and Z gates are vital quantum logic gates for all-optical systems. In this paper, the integrated all-optical Pauli X, Y, Z gate is realized using a square lattice 2D photonic crystal of silicon rods. The phase encoding and intensity encoding techniques have been used simultaneously for the integrated operation. Pauli X, Y, Z logic gate truth table has been verified at the operating wavelength of 1.55 µm.The system offers a linear operation, compact size, low power requirement, and high contrast ratio of 10.4 dB. The footprint of the proposed structure is about 70µm x 70µm and demonstrates a fast response time of 2 ps, bit rate of 0.25 Tbps, which makes it suitable for photonic integrated circuits (PICs). [ABSTRACT FROM AUTHOR]