Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.13020v1</id>\n    <title>Structured Quantum Optimal Control under Bandwidth and Smoothness Constraints-An Inexact Proximal-ADMM Approach for Low-Complexity Pulse Synthesis</title>\n    <updated>2026-03-13T14:27:40Z</updated>\n    <link href='https://arxiv.org/abs/2603.13020v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.13020v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>Quantum optimal control is often judged by nominal fidelity alone, even though realistic pulse-design studies must also account for bandwidth, amplitude, and smoothness constraints. I study this structured-control regime with an inexact Proximal-ADMM framework that combines gate-infidelity minimization with $L_1$ sparsity, total-variation regularization, explicit band-limit projection, and box constraints in a single loop. The method is benchmarked against GRAPE, standard Krotov, and L-BFGS-B on a single-qubit $X$ gate, a leakage-prone qutrit task, and a two-qubit entangling gate. Across ten random seeds, Pareto scans, ablations, filtered-baseline fairness checks, significance analysis with false-discovery-rate correction, and robustness tests, the method is not a universal winner in either nominal fidelity or wall-clock cost. Its value is instead to expose and stabilize a low-complexity frontier of the fidelity-complexity landscape. After retuning the PADMM budgets and warm-start lengths, the qutrit and two-qubit structured fidelities rise to 0.6672 +- 0.0001 and 0.6342 +- 0.0003, respectively, while preserving markedly lower complexity than unconstrained quasi-Newton solutions. These values remain well below deployment-grade gate thresholds, so the contribution should still be read as a numerical framework for constrained pulse synthesis rather than as a finished route to immediately deployable high-fidelity gates. Training-time robust optimization yields only task-dependent gains, with the clearest effect appearing in qutrit drift robustness and amounting to a small absolute improvement. The results therefore position PADMM as a constraint-native framework for low-complexity frontier exploration, not as a replacement for unconstrained high-fidelity solvers.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='quant-ph'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='physics.atom-ph'/>\n    <published>2026-03-13T14:27:40Z</published>\n    <arxiv:primary_category term='quant-ph'/>\n    <author>\n      <name>Ziwen Song</name>\n    </author>\n  </entry>"
}