Prof. Shlomi Arnon

Quantum computing based on photonic platforms offers a promising route toward scalable quantum information processing due to its low decoherence and access to high-dimensional state spaces. A promising approach for realizing photonic quantum computation is to encode quantum information in the Orbital Angular Momentum (OAM) states of light, enabling the realization of high-dimensional quantum gates. Implementing such quantum gates requires programmable unitary transformations between selected computational basis states. The fabrication of integrated multi-plane light conversion (MPLC) structures could provide a pathway toward large-scale programmable quantum processors. In this work, we investigate the implementation of photonic NOT-gate transformations using OAM states and MPLC systems with a limited number of phase planes. Unlike conventional MPLC approaches that optimize phase masks for a fixed modal basis, the proposed framework treats the computational basis itself as the optimization variable. To identify suitable computational basis states, a photonic quantum-gate optimization algorithm was developed to systematically evaluate candidate LG mode pairs. For each computational subspace, the three-plane MPLC phase masks were optimized using the wavefront-matching algorithm, and the corresponding modal and gate fidelities were calculated. The results show that conjugate-OAM mode pairs {LG_{p}^{l},LG_{p}^{-l}} and neighboring-radial mode pairs {LG_{p}^{l},LG_{p+1}^{l}} consistently achieve higher gate fidelity than structurally mismatched mode pairs under identical hardware constraints. These findings establish a direct relationship between computational-basis selection and quantum-gate performance, providing practical guidelines for computational-basis engineering in OAM-based quantum information processing, photonic quantum gates, and programmable quantum photonic processors.