Computação quântica: portas reversíveis fotônicas para obtenção de funções lógicas e portas controladas para qubits de estados coerentes

Abstract

Quantum computing, an approach based on quantum mechanics, enables information processingsignificantly faster compared to classical computing. While classical computing stores information in bits, which can be in either a 0 or 1 state, quantum computing uses qubits, whichcan be in a superposition of both states simultaneously, allowing calculations to be performedmuch faster than would be possible with classical computers. Among the various technologiescurrently employed in building a quantum computer, photonics-based technology is one ofthe most promising in the field. Thus, this work presents a theoretical and numerical study oftwo novel reversible gates (C1 and C2) for three coherent state qubits and an optical system toprobabilistically implement them. The proposed reversible gates differ only in the third output.The proposed optical system, which manipulates light beams, uses balanced beam splitters, phaseshifters, and photodetectors. This system can perform logical functions (AND, OR, NAND,and/or NOR) for two qubits simultaneously, with a success probability of up to 1/8 and a fidelityof over 90%. TheC1 andC2 gates can be cascaded to generate the C-NOT (and ¯C-NOT) gatewith a probability of up to 1/64. Therefore, the optical system presented offers flexibility andfeasibility for implementing reversible logical operations, with potential applications in quantumcomputing and information processing.