HALO Compiler Achieves Constant-Depth Trotter Steps for L=15 Schwinger Model String Dynamics on 16-Qubit Transmon Processor

The HALO architecture replaces standard Trotterization depth scaling with lattice size by compiling global evolution operators into fixed-depth circuits that act on composite multi-qubit gauge links. This enabled initialization and real-time evolution of a heavily stretched L=15 meson string, with Zero-Noise Extrapolation applied to extract the localized pair-creation crossover at t approximately 0.790 lattice units and an 18.3 plus or minus 2.2 percent rupture probability.

The work maps the mesoscopic dynamical phase diagram and locates the effective confinement boundary at g_c equals 1.0, while also providing a constant-depth 2D unit-cell blueprint that removes magnetic plaquette routing overhead. These steps directly address the coherence bottleneck that has limited prior digital LGT simulations on NISQ hardware.

Because the study remains a 2026 arXiv preprint and uses only 16 qubits, statistical power and hardware noise modeling remain modest; larger-scale fault-tolerant demonstrations will be required to confirm whether the O(1) scaling survives when logical qubits replace physical transmons.

The approach connects to earlier small-scale Schwinger simulations and ZNE error-mitigation benchmarks, suggesting a viable algorithmic route toward practical 2D QCD calculations once qubit counts and coherence improve.