These exploratory papers investigated distributional effects of decoherence in GHZ states. While several interesting observations were made, unresolved inconsistencies and lack of analytical grounding led us to treat these as internal exploratory work. Key conceptual lessons from these studies informed later, more general work on selective transcription.This archive contains a short research paper titled “Distributional Effects of Local Decoherence on GHZ Measurement Statistics.” The paper studies how local dephasing noise affects the full measurement outcome distributions of Greenberger–Horne–Zeilinger (GHZ) states when coherence is probed using a fixed rotated measurement basis. Rather than focusing on reduced density matrices or expectation values, the work analyzes decoherence at the level of empirical outcome histograms, using Jensen–Shannon divergence (JSD) as a bounded, information-theoretic metric. The central result is that, when GHZ states subjected to local dephasing are measured in a coherence-sensitive basis (implemented via a global Hadamard transformation prior to readout), the resulting outcome distribution exhibits a non-monotonic divergence from an ideal reference distribution. This divergence vanishes in both the fully coherent and fully dephased limits and attains a pronounced maximum at intermediate decoherence strength. The height and sharpness of this maximum increase with the number of qubits, reflecting the collective fragility of global coherence in GHZ states. The paper emphasizes that this effect does not arise for computational-basis measurements aligned with the dephasing channel, nor for product states or classical mixtures with matched marginals. The observed non-monotonicity therefore constitutes an operational signature of global multipartite coherence, rather than a generic consequence of noise or finite sampling. The archive includes: The complete LaTeX source of the paper. The compiled PDF. Figure files illustrating the Jensen–Shannon divergence curves. A short script used to generate the figures. The work is intended as a minimal, reproducible, and experimentally relevant diagnostic for coherence loss on noisy intermediate-scale quantum (NISQ) devices. It makes no interpretational claims and does not rely on state tomography, requiring only standard GHZ preparation, local dephasing, a fixed basis rotation, and histogrammed measurement outcomes.
These exploratory papers investigated distributional effects of decoherence in GHZ states. While several interesting observations were made, unresolved inconsistencies and lack of analytical grounding led us to treat these as internal exploratory work. Key conceptual lessons from these studies informed later, more general work on selective transcription.This archive contains a short research paper titled “Distributional Effects of Local Decoherence on GHZ Measurement Statistics.” The paper studies how local dephasing noise affects the full measurement outcome distributions of Greenberger–Horne–Zeilinger (GHZ) states when coherence is probed using a fixed rotated measurement basis. Rather than focusing on reduced density matrices or expectation values, the work analyzes decoherence at the level of empirical outcome histograms, using Jensen–Shannon divergence (JSD) as a bounded, information-theoretic metric. The central result is that, when GHZ states subjected to local dephasing are measured in a coherence-sensitive basis (implemented via a global Hadamard transformation prior to readout), the resulting outcome distribution exhibits a non-monotonic divergence from an ideal reference distribution. This divergence vanishes in both the fully coherent and fully dephased limits and attains a pronounced maximum at intermediate decoherence strength. The height and sharpness of this maximum increase with the number of qubits, reflecting the collective fragility of global coherence in GHZ states. The paper emphasizes that this effect does not arise for computational-basis measurements aligned with the dephasing channel, nor for product states or classical mixtures with matched marginals. The observed non-monotonicity therefore constitutes an operational signature of global multipartite coherence, rather than a generic consequence of noise or finite sampling. The archive includes: The complete LaTeX source of the paper. The compiled PDF. Figure files illustrating the Jensen–Shannon divergence curves. A short script used to generate the figures. The work is intended as a minimal, reproducible, and experimentally relevant diagnostic for coherence loss on noisy intermediate-scale quantum (NISQ) devices. It makes no interpretational claims and does not rely on state tomography, requiring only standard GHZ preparation, local dephasing, a fixed basis rotation, and histogrammed measurement outcomes.
These exploratory papers investigated distributional effects of decoherence in GHZ states. While several interesting observations were made, unresolved inconsistencies and lack of analytical grounding led us to treat these as internal exploratory work. Key conceptual lessons from these studies informed later, more general work on selective transcription.This archive contains the manuscript, figures, and reproducible simulation code accompanying the paper “Distributional Signatures of Entanglement Architecture under Misaligned Decoherence and Readout”. The work introduces a tomography-free, distribution-level diagnostic for multipartite coherence, demonstrating that endpoint Jensen–Shannon divergence under misaligned decoherence and readout provides an operational classifier of entanglement architecture.
This repository accompanies the preprint “Mapping the Limits of Architecture-Sensitive Noise Fingerprints in Quantum States.” The work investigates when and why simple classical measurement statistics obtained from noisy quantum systems retain information about the underlying quantum state architecture, and when such information collapses entirely. Building on earlier results demonstrating the existence of architecture-dependent classical fingerprints for stabilizer states under local noise, this study systematically maps the boundaries and failure modes of that phenomenon. Using exact probability distributions for small-to-moderate system sizes, we introduce controlled departures from stabilizer structure and track the degradation of classical features under dephasing and depolarizing noise. The analysis reveals sharply conditional survival of architecture sensitivity, a consistent feature-dependent collapse ordering, and a strong dependence on measurement basis and perturbation geometry. In particular, regimes of genuine diagnostic blindness are identified, where classical statistics become architecture-indistinguishable even though the underlying quantum states remain highly structured. The archive includes the full manuscript (PDF and LaTeX source), all figures appearing in the paper, the scripts required to reproduce the numerical experiments and figures, and the corresponding data outputs. All results are based on exact numerical evaluation (no sampling, optimisation, tomography, or machine learning). The work is intended as a lightweight, diagnostic limits study, providing practical guidance on when simple classical measurements are informative and when their use is fundamentally unreliable. Together with the companion papers in this series, the repository contributes to a coherent empirical and theoretical programme on the classical observability of quantum structure under noise.Version 1.1 notes.This revision clarifies the collapse criterion used to define architecture indistinguishability, explicitly specifies numerical precision and robustness checks, and adds a qualitative reliability chart summarising when different classical features remain informative. The presentation of noise-model dependence, system-size stability, and perturbation geometry has been sharpened, and the relationship to companion papers in the series has been made explicit. No new phenomena are introduced; the update improves transparency, interpretability, and practical usability of the results.
This archive accompanies the paper Architecture-Sensitive Noise Fingerprints in Classical Statistics of Quantum States. It contains the full manuscript, all figures appearing in the paper, and the Python scripts used to generate the numerical results. The project demonstrates that classical measurement statistics obtained from noisy quantum states retain reproducible, architecture-dependent structure. Even under standard local, Markovian noise models, simple low-order classical features—such as entropy, maximum probability, parity mass, and Hamming-weight distributions—encode diagnostic fingerprints of the underlying quantum state architecture. The analysis focuses on stabilizer states (including GHZ, cluster, and star graph states), fixed measurement bases, and exact probability distributions. No machine learning, optimisation, tomography, or state reconstruction is used. All results are generated using transparent, reproducible numerical simulations. The contents of this archive are: LaTeX source and compiled PDF of the manuscript All figures used in the paper (PDF/PNG) Python scripts for generating the figures and classical feature data A README describing structure and reproducibility This archive is intended to support transparency, reproducibility, and reuse of the results, and may serve as a lightweight reference for diagnostic approaches to quantum noise and state architecture.
We report a state- and observable-dependent retention advantage in operational fidelity proxies under dephasing-dominated noise across multiple quantum platforms. We do not claim enhanced off-diagonal GHZ coherence; rather, we compare measured observables with different channel sensitivities under identical physical noise: GHZ population fidelity Fpop = P(|00…0⟩) + P(|11…1⟩) (diagonal in the computational basis) versus an X-basis product-state control implemented as H⊗N → delay → H⊗N → measure. On IonQ Forte (5–20 qubits), parity visibility follows V(N) = 1.041 exp(−0.030N) with χ²/dof = 0.86 across 5–15 qubits. At 20 qubits, V departs by −8.2σ, consistent with correlated-noise onset; model comparison (AIC) favors a piecewise description with regime separation. On IBM Heron (3-qubit GHZ experiments), the fidelity advantage ΔF reaches 69.7 percentage points at maximum idle delay, with the population survival ratio G = 12.5× from raw counts without error mitigation. Three platforms with average two-qubit gate fidelities in the 94–98% range do not show a detectable advantage within our dataset, consistent with a graded performance dependence on hardware fidelity. The effect is GHZ-specific within our data: W-states and 1D cluster states show reduced fidelities (−12% and −38% relative to product controls), with no indication of protection. All fidelities are from raw shot counts; no ZNE, PEC, or post-selection was applied. These results motivate regime-aware benchmarks that treat the measured observable as a first-class experimental variable.
I report a hands-on, systematic investigation of Greenberger–Horne–Zeilinger (GHZ) state generation on a 127-qubit supercon-ducting quantum processor, covering system sizes from 4 to 80 qubits. I measured both computational-basis populations andglobal Pauli-X parity oscillations to decompose the state fidelity into its population purity and phase-coherence components. Mydata reveal an exponential collapse of fidelity with qubit number: a 4-qubit GHZ state achieves a fidelity of F = 0.9307, wellabove the threshold for entanglement-based quantum key distribution, yet by 32 qubits the fidelity has plummeted to 0.0963 andthe parity signal is extinguished. At 80 qubits, the state is indistinguishable from a maximally mixed state (F = 0.0453). I isolatethe dominant noise channels—CNOT gate errors, dephasing, readout crosstalk—and map the current usability frontier for rawmultipartite entanglement. I then contrast my results with mitigation-enhanced benchmarks from other platforms, showing thatadaptive compilation and dynamical decoupling can recover fidelity above the genuine multipartite entanglement (GME) thresholdeven at 120 qubits. This work provides a deeply personal, quantitative perspective on the challenges and near-term solutions forscaling entanglement in quantum communication, sensing, and error-mitigated computation.
We systematically characterize quantum entanglement in all sixteen combinations of two-qubit Bell states across three operational regimes: pure superposition, noiseless mixing, and asymmetric mixing of one noisy and one pure Bell state. For pure superpositions, we calculate the von Neumann entropy and show that entanglement depends critically on the relative phase phi between superposed states. For mixed states, we use concurrence C under three physically motivated decoherence channels. The Depolarizing (DP) and Phase Damping (PD) channels are modeled as global, collective operations on the two-qubit Hilbert space, while Amplitude Damping (AD) is treated as independent local decay on each qubit, reflecting the asymmetric, energy-dissipating nature of spontaneous emission. A central and counterintuitive result is that increasing noise can raise concurrence in specific parameter regimes across all three channels. We further map the boundary between mathematical entanglement (C > 0) and operational quantum non-locality using the Horodecki criterion, finding this boundary to be strongly channel-dependent. Under Phase Damping, the Bell-local entanglement regime vanishes entirely for identical and same-bases mixtures, meaning any surviving entanglement guarantees a CHSH violation. Under Depolarizing noise, a large Bell-local region requires mixing probability r > 1/sqrt(2) to recover non-locality at maximum noise. For Amplitude Damping, certain mixtures exhibit a non-monotonic Horodecki parameter M(T): concurrence decreases monotonically with noise, yet the capacity for CHSH violation is lost at intermediate noise levels and restored at high noise, as maximal damping repurifies the noisy branch. These results provide a unified analytical reference for entanglement and non-locality management across Bell-state combinations and decoherence channels relevant to NISQ architectures.