By Tarranix
Technology
The Toffoli gate is a well-known reversible logic gate capable of reproducing any logical component, ranging from simple logic circuits to complete Arithmetic Logic Units (ALUs). Its truth table is characterized by three inputs and three outputs. When both control inputs A and B are equal to 1, the target output C flips its logical value with respect to the input; otherwise, the output remains unchanged.
The Tarranix project implements this behavior using optical beam interference, allowing the logical operation to be fully controlled through guided-wave photonic structures.
The figures below present simulation results for two representative input configurations: 111 and 110.
Figure 1. Input 111, simulation in the XY plane and intensity of the three outputs
Figure 2. Input 110, simulation in XY plane and intensity of the 3 outputs
To quantify the gate performance, the reference intensity 𝐼𝐴′𝐵′ is defined as the average intensity of outputs A′ and B′. Under this definition, the target output C′ (the central guided wave) exhibits a normalized intensity of IC’ = 0,95 IA’B’ for input 110, while the intensity decreases to IC’ = 0,63 IA’B’ for input 111.
This clear intensity contrast demonstrates the successful implementation of a fully optical Toffoli gate. The team is currently working on further increasing this contrast, with the ultimate goal of cascading multiple gates to build complete optical logical circuits.
Tarranix developed a 6 µm vertical grating coupler for 3D photonic interconnections. Si/SiO₂ simulations show efficient light coupling. A Si₃N₄ version is in progress to enhance performance.
Tarranix has completed the first design phase of a photonic crystal (PhC) transistor with out-of-plane emission, adapted to the fabrication capabilities of UPC.
The Tarranix project has successfully completed simulations using a photonic crystal cross structure, making a key step in the development of optical logic with six logical states per transistor.
