Adjoint reversible simulator replay product (BL-39)

Versioned reverse-mode adjoint-via-replay product over ambient program_ad_adjoint generation and executable step replay. Materialised local scalar demos only; refuses mid-circuit measurement / irreversible invent-green, Catalyst parity, and hardware adjoint.

Module: scpn_quantum_control.adjoint_replay_product

Rules

Rule	Behaviour
Product schema	adjoint_replay_product.v1
Default surface	reverse_adjoint_grad
Mid-circuit measurement	Refused
Catalyst parity	Refused
Hardware adjoint	Refused
Blank/unknown surface	Fail closed
Full automatic checkpointing	Residual (S39.5+)

Claim boundary:

Adjoint reversible-replay product surface only; catalogues reversibility conditions, checkpoint policies, reverse-mode Program AD gradient, and executable adjoint step replay over ambient program_ad_adjoint; materialised local scalar demos only; refuses mid-circuit measurement / irreversible ops invent-green, Catalyst parity, and hardware adjoint; does not invent full automatic checkpointing, open-system reverse, or planner CI matrix (S39.5–S39.8 residual)

Public API

from scpn_quantum_control.adjoint_replay_product import (
    assert_adjoint_replay_product_integrity,
    build_adjoint_replay_product_registry,
    build_checkpoint_policy,
    decide_adjoint_replay_path,
    list_adjoint_replay_surface_ids,
    materialise_demo_adjoint_replay_probe,
)

assert "reverse_adjoint_grad" in list_adjoint_replay_surface_ids()
reg = assert_adjoint_replay_product_integrity(
    build_adjoint_replay_product_registry()
)

allowed = decide_adjoint_replay_path(has_supported_unitary_ir=True)
assert allowed.allowed is True

refused = decide_adjoint_replay_path(has_mid_circuit_measurement=True)
assert refused.allowed is False

# Worked demo: f(x,y)=x^2+y^2 at [0.5, -0.25] => grad [1.0, -0.5]
probe = materialise_demo_adjoint_replay_probe()
assert abs(probe.adjoint_gradient[0] - 1.0) < 1e-9
assert abs(probe.replay_gradient[1] + 0.5) < 1e-9
assert probe.agreement_max_abs < 1e-9

policy = build_checkpoint_policy(schedule="every_k", interval_k=2)
assert policy.interval_k == 2

Catalogue (S39.0)

ID	Kind
reversibility_conditions	predicates
checkpoint_policy	checkpoint schedule
reverse_adjoint_grad	reverse adjoint grad
executable_adjoint_replay	step-stream replay
irreversible_mid_circuit_refuse	irreversible refuse
catalyst_hardware_adjoint_refuse	Catalyst/hardware refuse

Worked scalar example

For f(x, y) = x^2 + y^2 at [0.5, -0.25]:

• value = 0.3125
• true gradient = [1.0, -0.5]
• ambient reverse adjoint and executable replay agree within 1e-12

Bounded product status

Shipped: S39.0 surface catalogue · S39.1 reversibility + checkpoint policy contracts · S39.3 reverse/replay materialised demo · irreversible / Catalyst / hardware refuse · docs / API map.

Open residual: S39.2 full checkpointed simulator campaign · S39.4 extended validation harness suite · S39.5 memory/time report artefacts · S39.6 planner registration matrix · S39.7 extended usage guide · S39.8 open-system reverse.

Authored by Anulum Fortis & Arcane Sapience (protoscience@anulum.li)