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.
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.
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.
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 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.
H. Billah and M.M.H. Sarker contributed equally to this work. Interpreting a fixed quantum circuit's output as evidence of a hardware effect requires ruling out two things usually conflated with it: finite-sample fluctuation, and structure already present in the circuit's own noiseless output. Less commonly checked is a third: whether the reference circuit compared against is the one actually executed, once compiler-level qubit routing is accounted for. We execute a fixed 35-qubit, 243-gate diagnostic circuit on IBM Heron-family hardware (three runs, two backends) and show this third check is essential: the routed circuit submitted to hardware has different noiseless predictions than the logical circuit intended, for several qubits. Against the correct, routed-circuit reference, the aggregate deviation is significant in two of three runs, and four registers (0, 9, 14, 27) show a significant output-probability deviation in every run — though we distinguish a high-confidence subset, {0, 9, 27}, with tightly time-matched calibration, from qubit 14, included only on an exploratory basis given its calibration was retrieved roughly two weeks post-execution. Same-backend replicates correlate more strongly by the Pearson measure, though a rank-based (Spearman) test shows this gap does not survive at the level of register ordering, indicating substantial leverage from a small number of registers rather than a broadly robust pattern; these three executions also share a byte-identical payload and are not independent replications in the strictest sense. The mechanism is only partially resolved: independent single-qubit readout error and raw gate count are ruled out as complete explanations for most of these registers, but the simplest version of the leading hypothesis for the single most-affected register does not reproduce the observed cross-backend pattern even with live, backend-specific timing data. A second, structurally different circuit validated only in simulation calibrates the statistical procedure's behavior under one synthetic noise model; it does not itself establish generality to real hardware, and the specific register set found here should not be expected to generalize beyond this study. Note on scope: this is a methodology and case-study contribution centered on executed-circuit references for fixed-circuit diagnostics, not a characterization of IBM Heron hardware in general or a randomized-benchmarking experiment in the formal sense. Supporting data, the routed OpenQASM circuits, raw measurement counts, and analysis code for this study are available on request from the corresponding author. Affiliation: Sonicium Quantum Lab Ltd., Dhaka, Bangladesh.
This preprint introduces and characterises a collective Fisher-information-inspired magnetisation-feedback term for Kuramoto--XY quantum simulations. The model augments a heterogeneous XY Hamiltonian with a diagonal term proportional to minus lambda times total magnetisation squared, normalised by qubit count, creating explicit magnetisation-sector energy shifts while preserving ideal XY magnetisation conservation. Artefact-generated exact diagonalisation on n = 4, 6, and 8 qubits shows systematic changes in ground energy, spectral width, and spectral gap as the feedback strength varies. The manuscript also reports adjacent-gap statistics, low-energy bipartition entropy trends, and a small n = 4 VQE benchmark comparing a K_ij-informed ansatz against generic TwoLocal and EfficientSU2 baselines. The record archives the source, bibliography, and PDF for a hardware-falsifiable modelling contribution. Claims are limited to the stated exact diagonalisation grid, VQE benchmark configuration, and associated committed artefacts.
We implement and benchmark on IBM Quantum hardware the circuit family proposed by Violaris for estimating operational inter-branch communication witnesses, defined as correlations in classical measurement records produced by compiled Wigner's-friend-style circuits. We realize a five-qubit instance of the protocol as an inter-register message-transfer pattern within a single circuit, rather than physical signaling, and evaluate its behavior under realistic device noise and compilation constraints. The circuit encodes branch-conditioned evolution of an observer subsystem whose dynamics depend on a control qubit, followed by a controlled transfer operation that probes correlations between conditional measurement contexts.
Executing on the ibm_fez backend with 20000 shots, we observe population-based visibility of 0.877, coherence witnesses of 0.840 and -0.811 along orthogonal axes, and a phase-sensitive magnitude of approximately 1.17. While the visibility metric is insensitive to some classes of dephasing, the coherence witnesses provide complementary sensitivity to off-diagonal noise.
This work does not test or discriminate among interpretations of quantum mechanics. Instead, it provides a reproducible operational constraint pipeline for evaluating detectability of non-ideal channels relative to calibrated device noise.