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 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 methods preprint describes the software and experimental workflow behind scpn-quantum-control, an open-source framework for mapping heterogeneous Kuramoto-type oscillator networks to XY spin Hamiltonians, compiling topology-informed variational ansatze, benchmarking simulation paths, and executing reproducible NISQ hardware experiments. The workflow combines Python/Qiskit orchestration with a Rust/PyO3 acceleration layer for hot-path kernels including coupling-matrix construction, Hamiltonian assembly, trajectory features, hybrid digital--analog partitioning, and protected-subspace diagnostics. The manuscript reports artefact-generated timings across local workstation, ML350, Vertex AI CPU, and Vertex AI Tesla T4 contexts, with checksum parity across Python, Rust, and Go kernels. The record includes manuscript source, notes bibliography, and PDF. It is an archival methods record for the repository and its reproducibility artefacts, not an independent claim of broad quantum advantage.
Periodically driven interacting quantum many-body systems can exhibit long-lived prethermal dynamics, where local observables retain coherent structure even as entanglement and operator complexity grow. Accessing this regime at the system sizes and times needed to determine physical properties of the prethermal state remains a central challenge: state-of-the-art classical methods become unreliable, while noise in quantum hardware degrades observable expectation values. Here we overcome these limitations for a Floquet Ising magnet realized on a heavy-hex lattice. Using the advanced error mitigation software QESEM on an IBM Heron r3 superconducting quantum processor, we measure magnetization dynamics with percent-level precision and resolve long-lived subharmonic prethermal oscillations in systems of up to 74 qubits. These experiments reach regimes for which leading tensor-network simulations fail to converge, while sparse Pauli-path simulations remain strongly truncation dependent despite extensive computations on advanced GPUs and the Fugaku supercomputer. Leveraging this quantum-accessible regime, we extend finite-size scaling to larger systems and find an unexpectedly slow decrease of the oscillation amplitude with system size, providing strong evidence that this oscillatory response persists in the thermodynamic limit of heavy-hex ladders. A hierarchy of mitigation and validation tests, including unbiased error mitigation, agreement between independent mitigation estimators, noise-model validation on the superconducting hardware, and cross-platform corroboration at selected Floquet cycles on Quantinuum System Model H2 and Quantinuum Helios trapped-ion hardware, supports the reliability of these findings. Our work establishes error-mitigated quantum processors as quantitative scientific instruments for discovering new physics in non-equilibrium quantum matter.
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.
Can systems matched on a declared present nevertheless show different future responses because they retain different relational organisation? We test this in a six-qubit hybrid quantum-classical architecture on IBM Heron hardware. Written and sham preparations use exactly the same five coupling values and the same number of native two-qubit operations; only the edge assignment differs. Under a frozen preregistered decision rule with randomised block orders, matched fast preparations displayed different later directional responses when the prepared slow classical relational configuration differed. Because the full-sample cosine alignment and norm-based retention estimates sat outside their original percentile intervals, a post hoc audit was performed from the sealed raw-count archive. That audit is reported alongside, and does not replace, the frozen rule. Claim boundary. The result is real under its frozen analysis. It is not autonomous cross-job quantum memory, and it is not evidence of a hidden quantum degree of freedom persisting between jobs. The classical coupling configuration is part of the preparation and is named as such throughout. No claim is made about quantum coherence surviving between executions. This deposit contains the manuscript in PDF and DOCX form together with the complete evidence archive: protocol freezes, compiled QPY circuits, inspection tables, randomised block orders, backend snapshots, raw-count files for both runs, IBM job ledgers, point estimates, blockwise endpoints, the frozen decision JSON, an artefact inventory and a checksum ledger.
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.