A Discrete-Lattice Numerical Simulation of Near-Field Electron Diffraction and Environmental Decoherence

We present a highly efficient discrete-lattice numerical method for simulating electron wavepacket propagation, diffraction, and environmental decoherence without relying on continuum ap- proximations. By executing an exact unitary quantum walk on a finite truncated square (4.8.8) lattice, the model natively bridges the near-field (Fresnel) and far-field (Fraunhofer) regimes. The approach avoids the numerical sign problem typical of Monte Carlo path sam- pling and naturally accounts for waveguide collimation effects from finite-thickness physical slits. The simulation yields double-slit interference profiles in close quantitative agreement with empirical nanoscale data. Furthermore, by introducing an orthogonal ancillary lattice dimension, we provide a computationally lightweight method for simulating exact environ- mental decoherence, generating classical Born rule statistics directly from unitary evolution. 2026-06-20 legacy erratum: This version adds a canon erratum note to the legacy paper. Numerical diffraction/decoherence note; likely mostly independent The body is preserved as a historical derivation trail; the erratum note identifies the current ANCHOR/DRIFT status and superseded claims. 2026-06-21 canon refresh: This version incorporates the 2026-06-21 ANCHOR/DRIFT/PTMS canon refresh and rebuilt local PDF.