Simulating Universal Quantum Gate Sets on Photonic OAM Qubits: Single-Qubit and Multi-Qubit Operations via Spatial Light Modulator Phase Holography
Spatial light modulators (SLMs) have emerged as reconfigurable platforms for photonic quantum information processing, offering software-defined control over the orbital angular momentum (OAM) of light encoded in Laguerre-Gaussian (LG) beams. This paper presents a comprehensive simulation and hardware-grounded fidelity analysis of quantum gate operations implemented on the HOLOEYE LC 2012 transmissive SLM. A realistic three-channel noise model comprising 8-bit quantisation noise, twisted-nematic (TN) electronic and thermal noise, and phase-wrap clipping error is obtained from the manufacturer's datasheet without free-parameter fitting, yielding a total noise of $σ_{\text{total}} = 92.4\text{mrad}$. The complete universal single-qubit gate set $\{X, Y, Z, S, T, H\}$ and two-qubit entangling gates $\{\text{CNOT}, \text{CZ}, \text{SWAP}\}$ are simulated on a $512 \times 512$ computational grid. Results show that predicted gate fidelity are in the range of $F = 0.9914\text{--}0.9936$, with fork grating gates limited primarily by TN noise and phase gates achieving higher fidelity owing to zero phase-wrap clipping error. In addition, Bell state preparation via the H-CNOT circuit achieves $F(Φ^+) = 0.9914$ after two SLM interactions. We benchmark our obtained results against six published experimental studies spanning the 78%--99.6% fidelity range. Finally, a wavelength-dependent analysis identifies 450--532 nm operation as the optimal regime for this device.