Cryogenic control electronics accumulate systematic, non-zero-mean bias — from thermal cycling of mounts, flux leakage, and dielectric memory — that a feedback loop integrates until its actuator authority is exhausted and the integrator saturates. A controller that alarms on amplitude thresholds sees this failure only after correction is no longer available. This paper reports a precursor estimator that reads the dynamics of the control signal for the onset of systematic drift, built deliberately as a finite observer in the sense of the first Finite Cognition paper: a declared error budget, an explicit competence boundary, and fail-closed abstention. Its evidence is presented in two declared strata. First, a fresh, fully archived Monte-Carlo run of record on a declared control-loop model: across 30 seeds × 7 sensor-environment conditions × two drift polarities, with every threshold frozen before the batch, the estimator detected drift before saturation in 246/354 eligible collapse runs (69.5%, 95% interval 64.5–74.1%), with per-condition detection ranging from 25.5% (all disturbances combined) to 100% (dropout; 92.4–100), median leads of 7–17 s, and zero false interdicts across 210 healthy runs within the declared calibration window (0.0–1.8%) — a bound the long-horizon batch shows is conditional on the mandated recalibration schedule. Second, an archived read of live IBM quantum-hardware calibration telemetry (a 156-qubit Heron device, June 2026): the same governed detector family flagged the two genuinely degraded qubits and the sole sustained relaxation-time decline within that window (T_1 falling 88.0 → 19.1 µs across 43 returned calibration snapshots spanning 42 calendar days) — an event a longer archived record later resolves into the first, longest and deepest of four recurring excursions on the same qubit, at a cost to this detector family the paper states while staying silent on a bad-but-stable qubit and the 154 others. The estimator holds advisory-only authority under the programme's interface contract: it emits verdicts and writes nothing to the plant. This record supersedes an earlier version whose simulation table could not be traced to a quantum-specific run; the run of record reported here, code and data archived, is the evidence this paper stands on.
Cryogenic control electronics accumulate systematic, non-zero-mean bias — from thermal cycling of mounts, flux leakage, and dielectric memory — that a feedback loop integrates until its actuator authority is exhausted and the integrator saturates. A controller that alarms on amplitude thresholds sees this failure only after correction is no longer available. This paper reports a precursor estimator that reads the dynamics of the control signal for the onset of systematic drift, built deliberately as a finite observer in the sense of the first Finite Cognition paper: a declared error budget, an explicit competence boundary, and fail-closed abstention. Its evidence is presented in two declared strata. First, a fresh, fully archived Monte-Carlo run of record on a declared control-loop model: across 30 seeds × 7 sensor-environment conditions × two drift polarities, with every threshold frozen before the batch, the estimator detected drift before saturation in 246/354 eligible collapse runs (69.5%, 95% interval 64.5–74.1%), with per-condition detection ranging from 25.5% (all disturbances combined) to 100% (dropout; 92.4–100), median leads of 7–17 s, and zero false interdicts across 210 healthy runs within the declared calibration window (0.0–1.8%) — a bound the long-horizon batch shows is conditional on the mandated recalibration schedule. Second, an archived read of live IBM quantum-hardware calibration telemetry (a 156-qubit Heron device, June 2026): the same governed detector family flagged the two genuinely degraded qubits and the sole sustained relaxation-time decline within that window (T_1 falling 88.0 → 19.1 µs across 43 returned calibration snapshots spanning 42 calendar days) — an event a longer archived record later resolves into the first, longest and deepest of four recurring excursions on the same qubit, at a cost to this detector family the paper states while staying silent on a bad-but-stable qubit and the 154 others. The estimator holds advisory-only authority under the programme's interface contract: it emits verdicts and writes nothing to the plant. This record supersedes an earlier version whose simulation table could not be traced to a quantum-specific run; the run of record reported here, code and data archived, is the evidence this paper stands on.
Cryogenic control electronics for quantum hardware accumulate systematic, non-zero-mean bias that integrates in a feedback loop until the actuator saturates; a threshold controller detects this only after saturation. We present a precursor estimator that detects the onset of systematic drift from the dynamics of the control signal, built as a finite observer (declared error budget, explicit competence boundary, fail-closed abstention) in the sense of a companion paper on the physical limits of finite observation. It uses path-functional invariants (a Fisher–Rao metric stability bound, a maximum-likelihood bias decoder, a cumulative-damage functional) rather than eigenvalue analysis, which we show is neither necessary nor sufficient for finite-time survival. In simulation, across 30 seeds × 7 sensor-environment conditions (including a 1/f dephasing spectrum), it detects 96.7% of drift-collapse scenarios before saturation at a 12 s median lead with 0% false positives over 210 healthy runs. On real data, the same governed outlier-and-drift detector, applied to live publicly accessible IBM quantum-hardware calibration time-series (a 156-qubit IBM Heron device), flags genuinely degraded qubits and catches a real relaxation-time decline (one qubit's T1 falling 88.0→19.1 µs, −78%, over 43 days) while staying silent on a qubit that is poor but stable and on the other 155 — detection of change, not of mere badness. The work is TRL 4: an advisory detection layer, not a deployed controller, and it does not emulate entanglement, non-local correlation, or contextuality. The contribution is the integrated, calibrated estimator and its operating discipline, demonstrated in simulation and against real hardware-calibration data.
Cryogenic control electronics for quantum hardware accumulate systematic, non-zero-mean bias that integrates in feedback loops until actuator saturation. We present a precursor estimator that detects the onset of systematic drift from control-signal dynamics before saturation. Designed as a finite observer, it operates to a declared error budget, carries an explicit boundary of competence, and abstains—fails closed—outside it. The estimator uses path-functional invariants rather than eigenvalue or linearisation analysis. In simulation across 30 seeds and seven sensor-environment conditions, it detects 96.7% of drift-collapse scenarios before saturation, with a 12-second median lead and 0% false positives across 210 healthy runs. Applied to live, publicly accessible IBM quantum-hardware calibration time-series from a 156-qubit IBM Heron device, it flags degraded qubits and detects a real relaxation-time decline while raising no alarm on a poor-but-stable qubit or the remaining 155 qubits. This is a TRL-4 detection layer: advisory, validated in simulation and on hardware calibration data, and not a deployed controller.
A companion paper reported a fail-closed estimator — the Quantum Control Kernel (QCK) — that detects the precursor of systematic bias drift in cryogenic quantum control before actuator saturation, validated in simulation and against live, publicly accessible IBM hardware-calibration data. This paper reports what the estimator is for: the Quantum Control Architecture (QCA), a governed measurement-and-control layer in which the demonstrated kernel is the sensing floor of a larger construction. The construction is not free design. It is the quantum instantiation of a result established generically in the Finite Cognition series: a finite observer serving both a committing execution demand and a wide-field vigilance demand is forced to partition the two and re-couple them at the point of finalisation, so that no output is committed that vigilance has not verified. We show that quantum control information forces exactly this construction — telemetry is consumed by every layer of the control stack yet governed by none of them; observation of a quantum plant must be non-perturbative by discipline, not by hope; and an estimator that is fluent but ungoverned reproduces, on the control substrate, the same confident-and-blind failure the series identified generically. We then state the architecture that discharges the constraint, in its public units: a non-perturbative observer (NPO); the QCK detection floor; fail-closed gates that allow, abstain, or refuse; a state-coherence and equilibrium discipline over commits; provenance-checked memory that refuses known-failure patterns; a lifecycle and loop supervisor; a measurement plane of stability, coupling, margin, and cost features; and an integrity plane that audits the architecture’s own calibration model and gates its portability to new hardware on provably leak-free relocation. We are explicit about maturity throughout: the kernel is demonstrated at Technology Readiness Level 4 under published bounds; the architecture beyond it is compile-ready geometry — derived, specified, and internally consistent, not validated as live middleware on partner hardware. The architecture is advisory by construction: the operator owns the plant at every depth.
A companion paper reported a fail-closed estimator — the Quantum Control Kernel (QCK) — that detects the precursor of systematic bias drift in cryogenic quantum control before actuator saturation, validated in simulation and against live, publicly accessible IBM hardware-calibration data. This paper reports what the estimator is for: the Quantum Control Architecture (QCA), a governed measurement-and-control layer in which the demonstrated kernel is the sensing floor of a larger construction. The construction is not free design. It is the quantum instantiation of a result established generically in the Finite Cognition series: a finite observer serving both a committing execution demand and a wide-field vigilance demand is forced to partition the two and re-couple them at the point of finalisation, so that no output is committed that vigilance has not verified. We show that quantum control information forces exactly this construction — telemetry is consumed by every layer of the control stack yet governed by none of them; observation of a quantum plant must be non-perturbative by discipline, not by hope; and an estimator that is fluent but ungoverned reproduces, on the control substrate, the same confident-and-blind failure the series identified generically. We then state the architecture that discharges the constraint, in its public units: a non-perturbative observer (NPO); the QCK detection floor; fail-closed gates that allow, abstain, or refuse; a state-coherence and equilibrium discipline over commits; provenance-checked memory that refuses known-failure patterns; a lifecycle and loop supervisor; a measurement plane of stability, coupling, margin, and cost features; and an integrity plane that audits the architecture’s own calibration model and gates its portability to new hardware on provably leak-free relocation. We are explicit about maturity throughout: the kernel is demonstrated at Technology Readiness Level 4 under published bounds; the architecture beyond it is compile-ready geometry — derived, specified, and internally consistent, not validated as live middleware on partner hardware. The architecture is advisory by construction: the operator owns the plant at every depth.
Quantum control practice runs on characterisations: measured coherence times, gate errors, frequencies, and crosstalk figures, taken at calibration and consumed by every layer of the control stack until the next calibration replaces them. A premise rides silently in that consumption — that the characterisation remains current between calibrations — and this paper examines and refuses it. We argue three points, each held at its own strength. First, a characterisation is a finite observer's estimate, not a standing fact: at calibration time it already carries a strictly positive uncertainty floor from finite probes, and the act of probing is itself a physical intervention on the device. Second, between calibrations the device's parameters move — relaxation times fluctuate on hour scales through two-level-system dynamics, and environmental drift reshapes the error landscape — so the uncertainty a consumer should attach to a characterisation widens with time since calibration under any honest model. Third, these two facts compose into a limit with an operational consequence: under the declared drift model a characterisation carries a finite validity horizon, and in every case it carries expiry semantics — a control stack that consumes a characterisation without an expiry is acting on an unexamined exactness claim. The finite horizon is conditional and the finite-calibration limit section states its converse: a mean-reverting drift confined within tolerance admits an infinite horizon, and nothing here forbids that case. We then instantiate the external contract of the companion limits paper for this setting: a characterisation ships with a declared validity budget and a declared expiry model; consumers check validity before acting on it; and on expiry the fail-closed forms are refusal of the stale figure and escalation to recalibration with a declared deadline. We state a minimal stochastic validity model — latent device state, calibration posterior, hazard-widening between calibrations, derived expiry rule — as a declared model whose parameters an installation must estimate, not a law derived here. The authority boundary of the resulting layer is advisory by design choice, and we give the rationale rather than presenting the choice as a consequence. Related work has built the detection and tracking instruments this contract would consume; what is added here is the register those instruments lack: validity as a first-class, expiring, refusable claim.
Description This work introduces the Systolic Drift Monitor (SDM), a universal hardware safety layer designed to address a fundamental limitation in real-time quantum error correction (QEC): the inability of finite-window decoders to detect slow, non-Markovian drift such as 1/f noise. We formalize this limitation as the Lag Horizon, an information-theoretic blind spot arising from finite memory and boundary-only observation. Using the Fisher-Blindness No-Go Theorem, we show that when error correlations extend beyond the decoder window, the Fisher information available to any windowed observer vanishes, rendering structural phase transitions statistically undetectable regardless of processing speed. To resolve this blindness, we propose the SDM as a minimal, architecture-independent hardware primitive that operates alongside—rather than within—the primary decoder. Implemented on 2025-era FPGA platforms (AMD Versal ACAP and Intel Agilex), the SDM performs deterministic, infinite-horizon integration of syndrome flux, restoring visibility to topological drift while maintaining constant latency. We analyze two experimentally relevant regimes: Superconducting dual-rail qubits, where the SDM functions as an asynchronous drift watchdog for long-timescale flux noise (>100 μs) despite sub-microsecond QEC cycles. Neutral atom processors, where large cycle times (>1 ms) allow the SDM to operate as a hard safety interlock, converting atom loss and leakage precursors into flagged erasures before logical failure. Simulation-based validation across surface codes and color codes demonstrates pre-symptomatic detection of non-Markovian faults and negligible hardware overhead (<0.1% FPGA resources, O(d) scaling). The SDM reframes fault tolerance from continuous local correction to interventionist safety, analogous to circuit breakers in classical control systems. This work is intended for researchers and engineers in quantum error correction, quantum control hardware, FPGA-based systems, and fault-tolerant quantum architectures, and is presented as an engineering and information-theoretic contribution, not a proposal of new physical laws.