This preprint reports a preregistered dynamic-circuit quantum-control experiment comparing monitored feedback against matched open-loop control for a four-qubit Kuramoto--XY synchronisation payload. The experiment uses three system qubits, one monitor qubit, and three dynamic rounds to test feedback directly on IBM gate-model hardware. The primary ibm_kingston binary endpoint is negative: the monitored-feedback arm does not improve the selected target relative to the matched open-loop control. The same S1--S1f stack is then replicated on ibm_fez and ibm_marrakesh, where the primary endpoint is positive but direct-observable extensions show backend-dependent YYI and response structure. The contribution is therefore a hardware-control boundary result: it documents where the monitored-feedback policy fails, where it appears to improve the selected target, and why the result should not be interpreted as a simple backend-independent controller promotion. The record includes the source, bibliography, and rebuilt PDF.
This preprint reports a preregistered dynamic-circuit quantum-control experiment comparing monitored feedback against matched open-loop control for a four-qubit Kuramoto--XY synchronisation payload. The experiment uses three system qubits, one monitor qubit, and three dynamic rounds to test feedback directly on IBM gate-model hardware. The primary ibm_kingston binary endpoint is negative: the monitored-feedback arm does not improve the selected target relative to the matched open-loop control. The same S1--S1f stack is then replicated on ibm_fez and ibm_marrakesh, where the primary endpoint is positive but direct-observable extensions show backend-dependent YYI and response structure. The contribution is therefore a hardware-control boundary result: it documents where the monitored-feedback policy fails, where it appears to improve the selected target, and why the result should not be interpreted as a simple backend-independent controller promotion. The record includes the source, bibliography, and rebuilt PDF.
We investigate whether a training-free thermodynamic stability metric Φ = I × ρ - α × S, computed from IBM Quantum calibration or telemetry data, can drive closed-loop intervention decisions during execution-associated monitoring windows on real hardware. Across 10 paid circuit tests on three IBM backends (ibm_fez, ibm_marrakesh, ibm_torino), together with simulated and telemetry-based harness validation, we evaluate a closed-loop controller that monitors Φ during an execution-associated window and supports five intervention actions: CONTINUE, CONTINUE-DEGRADED, CLASSICAL-FALLBACK, CHECKPOINT-MIGRATE, and ABORT-RESTART. In a same-circuit controlled comparison on ibm_fez, swapping LOW-Φ qubits (Φ = 0.097, 0.030) for HIGH-Φ qubits (Φ = 0.9988, 0.9984) reduced error from 18.36% to 2.73% on an identical Deutsch-Jozsa circuit, an 85.1% relative error reduction. Under matched conditions, composite Φ selection outperformed raw T2 selection by 7.79 percentage points on ibm_fez (68.7% relative reduction) and by 6.37 percentage points aggregate across three backends. Mid-circuit dynamic branching on IBM hardware achieved 98.78% per-shot conditional consistency between probe outcome and branch marker, with an estimated 101,220 logical gates avoided on the ABORT path. A Wilson confidence interval non-overlap rule triggered ABORT-RESTART on 1 of 3 backends in the tested setting. Classical checkpoint representation at a segmentation boundary enabled suffix migration from LOW-Φ to HIGH-Φ qubits with 82.15% final fidelity, without storing an unknown quantum state. Honest counterexamples are preserved: in a three-policy cost comparison a seeded random pair outperformed the Φ-guided pair on ibm_fez, and on ibm_marrakesh raw T2 selection outperformed Φ selection under matched compiled circuit conditions. These results support a closed-loop intervention framework in which Φ can operate as a control variable during execution-associated monitoring rather than only as a pre-execution selection score. The methods described in this paper are the subject of U.S. Provisional Patent Application No. 63/973,723 (filed February 2, 2026). No license to implement or commercialize the described methods is granted by this publication. All rights reserved.
This preprint reports a bounded IBM Heron hardware observation of parity-sector and excitation-number correlated decoherence asymmetry in small XY-Hamiltonian circuits. The dynamical Lie algebra of the XY Hamiltonian decomposes under the parity operator, and the experiment measures parity leakage rates across labelled sectors without promoting the observation as a DLA-only causal effect. The archived study uses a 342-circuit campaign on IBM ibm_kingston (Heron r2, 156 qubits), with n = 4 circuits across eight Trotter depths. It reports an odd-sector leakage excess over the even sector, with seven of eight tested depths individually significant under Welch tests, while explicitly treating shared-qubit and shared-calibration context as a boundary on inference. The record includes the manuscript source and PDF for a reproducible archival preprint. Claims are limited to the named hardware campaign, committed raw-count artefacts, stated reducers, and the open repository at https://github.com/anulum/scpn-quantum-control.
Programmable quantum hardware provides an emerging platform for exploring and controlling non-unitary quantum dynamics through measurement-based operations. In this work, we introduce feedback-directed circuit architectures that integrate spatially structured mid-circuit measurements with real-time conditional operations to steer the evolution of random dynamics, and perform their large-scale simulations (up to 100 qubits) on programmable digital quantum processors. By promoting measurement from a passive readout to an active control signal, these adaptive monitored circuits enable directional information flow and generate intrinsic asymmetry in random circuit simulations. We implement this framework on IBM superconducting quantum processors and observe robust, noise-resilient signatures of feedback-induced asymmetry distinct from the more well-known non-Hermitian skin effect. Our results establish feedback as a programmable resource for non-unitary control, opening new avenues for engineering measurement-based dynamics, non-equilibrium phenomena, and tunable open-system behavior on large-scale quantum hardware.
This preprint presents a Kuramoto--XY synchronisation study with heterogeneous natural frequencies, simulator baselines, and ledgered IBM Heron r2 evidence. A Rust/PyO3-assisted pipeline supports entanglement entropy, Krylov complexity, OTOC scrambling, and Floquet discrete-time-crystal diagnostics for 2--16 qubit systems. The manuscript reports finite-size diagnostics consistent with Berezinskii--Kosterlitz--Thouless scaling in the small systems studied, including a periodic-boundary central-charge estimate near c = 1 at n = 8, while explicitly noting finite-size drift at larger sizes. It also records subharmonic Floquet response, non-ergodic level-spacing behaviour for heterogeneous frequencies, and a hardware-anchored scaling analysis that bounds exact Hilbert-space simulation costs. The record archives the manuscript source and PDF. Legacy IBM artefacts are treated as committed artefact-path evidence rather than aggregate validation, and the resource-boundary discussion is not promoted as a broad quantum-advantage claim because classical Rust Kuramoto ODE baselines remain faster in the measured observable-level regime.
This preprint reports a cost-bounded reduced-Pauli entanglement and tomography check for promoted Phase 3 DLA-parity and Fisher-information-modified Kuramoto--XY circuit families. The purpose is to distinguish parity-sector leakage structure from layout, prepared-state, and readout artefacts in small superconducting-hardware experiments. The archived IBM execution used physical qubits [1,2,3,4] on ibm_marrakesh, 162 main circuits, four readout-calibration circuits, 2048 shots per main circuit, and 8192 shots per readout circuit. A preregistered reducer produced 54 observable rows; the manuscript reports measured-minus-exact deviations, identifies the largest transverse two-qubit correlator deviations, and compares readout-mitigated replay and same-day ibm_fez replication. The record includes manuscript source, bibliography, and PDF. The claim boundary is hardware-observation and artefact-reduction evidence for these named circuit families, not a backend-independent universal promotion.
Preregistered, one-run hardware characterization of a verification-before-execution boundary using mid-circuit measurement and dynamic-circuit feed-forward on ibm_kingston (job d9ajf3eg26ic73deq3l0, 4096 shots/arm). Preregistered kill-condition: DENY-leakage ≤ 3%. Measured: 12.62% → FAIL. Post-hoc analysis (zero evidential weight): leakage is indistinguishable from the idle-control readout baseline (13.50%), indicating measurement noise, not feed-forward misfire, sets the certification floor. Standalone work; separate from the UIP Phase 1 record. No claim of new physics. Code, preregistration, and raw results: github.com/derekhone/uip-phase1-testbeds (vbe1/).