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Engine quan_loncar_v1 · package package/quan_loncar_optimizer · assembled 2026-07-29 15:57 UTC.

Architecture

Preserved physics layer

engine/ is the unchanged historical solver. The production adapter imports:

  • geometry and exact constraint logic from phases 14, 26, and 45;
  • the converged y3-z1 cross-section basis from phases 50 and 53;
  • the P2-z1 hole basis from phases 51 and 54;
  • outgoing pole-subtracted radiation and corrected complex poles from phases 33 and 34;
  • corrected QNM normalization, geometry JVP, objective VJP, and coupling VJP from phases 39–44;
  • the accepted Phase-55/57 autograd configuration.

The adapter in src/quan_optimizer/engine.py exposes two operations:

  • solve_pole: a fresh branch-tracked complex-pole solve at one geometry;
  • evaluate_from_pole: the complete local observables and 45-coordinate custom VJP at that converged pole.

Optimization layer

optimizer.py is a restartable state machine.

verified seed
  -> full pole + VJP
  -> projected direction
  -> trust-limited line search
  -> fresh pole gate
  -> full VJP gate
  -> atomic checkpoint
  -> matched FDTD checkpoint
  -> accept or rollback

The complex-pole prediction from the resonance gradient is never accepted as a solution. It is only the initial guess for the next nonlinear solve.

Geometry

The vector is:

[15 positive-side gaps, 15 x radii, 15 y radii]  (nanometres)

Mirror symmetry reconstructs 30 physical holes. Conversions between the portable FDTD JSON schema and the engine vector are covered by round-trip tests.

FDTD layer

fdtd/nanobeam_fdtd/ is the preserved confirmation package. It builds one nominal simulation or a five-case convergence panel, submits only when --submit is present, analyzes harmonic inversion, and compares two designs.

The optimizer and FDTD dependencies are intentionally separated so an analytical run does not require cloud credentials.

Audit tools

  • run_preflight.py: engine hashes, seed integrity, optional physical pole and gradient.
  • run_basis_audit.py: production versus stricter continuum/basis settings.
  • make_validation_panel.py: local FDTD directional falsification panel.
  • render_report.py: regenerates the run's dependency-free HTML report.
  • record_fdtd_checkpoint.py: the only supported mutation of FDTD incumbent state.

Backward compatibility

Backward compatibility means preserving the successful physical engine and geometry, not preserving unsafe campaign behavior. The new wrapper intentionally removes:

  • accepting a linearized pole without a fresh nonlinear solve;
  • carrying a stale derivative across accepted geometries;
  • long blocks without FDTD;
  • comparing a candidate against unmatched simulation settings;
  • replacing the FDTD incumbent with a rejected result;
  • treating the unverified Phase-58 Q=30,307 continuation as trusted.