This work develops a structural framework for accessibility-loss events in open-system decoherence under fixed control. Instead of focusing on externally tuned filter-function changes, the analysis centers on the reduced decoherence functional χ(T), which is decomposed into positive effective contributions within an additive Gaussian description. An accessibility-loss event is defined as a fixed-control transition in which one effective contribution ceases to participate within the coherence-estimation window. The primary invariant of the event is the event amplitude f(T)=1−χpost(T)χpre(T), which measures the lost fraction of the pre-event decoherence functional. We show that f(T) is scale-invariant, depends only on participation structure, and that event existence is equivalent to f(T)>0. Numerical ratios such as pre/post coherence-time ratios are therefore derived quantities, not defining features of the event. A sharp-switch limit is derived: when the suppression timescale is short compared with the estimation window and the remaining background varies more slowly, a smooth microscopic suppression appears as an effectively discontinuous jump in window-averaged observables. This leads to a two-layer falsification structure: (1) falsification of event existence (whether f>0), and (2) falsification of subclass-specific benchmark values. As an illustration, we identify a symmetric normalized subclass in which the fluctuation-sector contributions satisfy a normalized isotropic structure, yielding f=14,R=TpostTpre=43 within the single-rate regime. These values are not universal constants of open-system decoherence but benchmark invariants of this restricted structural subclass. The framework clarifies that decoherence encodes not only spectral and control information but also participation structure—which effective contributions are active within the observation window and when that participation changes. Accessibility-loss events thus represent structurally identifiable transitions in reduced decoherence geometry, independent of microscopic realization.
This work develops a structural framework for accessibility-loss events in open-system decoherence under fixed control. Instead of focusing on externally tuned filter-function changes, the analysis centers on the reduced decoherence functional χ(T), which is decomposed into positive effective contributions within an additive Gaussian description. An accessibility-loss event is defined as a fixed-control transition in which one effective contribution ceases to participate within the coherence-estimation window. The primary invariant of the event is the event amplitude f(T)=1−χpost(T)χpre(T), which measures the lost fraction of the pre-event decoherence functional. We show that f(T) is scale-invariant, depends only on participation structure, and that event existence is equivalent to f(T)>0. Numerical ratios such as pre/post coherence-time ratios are therefore derived quantities, not defining features of the event. A sharp-switch limit is derived: when the suppression timescale is short compared with the estimation window and the remaining background varies more slowly, a smooth microscopic suppression appears as an effectively discontinuous jump in window-averaged observables. This leads to a two-layer falsification structure: (1) falsification of event existence (whether f>0), and (2) falsification of subclass-specific benchmark values. As an illustration, we identify a symmetric normalized subclass in which the fluctuation-sector contributions satisfy a normalized isotropic structure, yielding f=14,R=TpostTpre=43 within the single-rate regime. These values are not universal constants of open-system decoherence but benchmark invariants of this restricted structural subclass. The framework clarifies that decoherence encodes not only spectral and control information but also participation structure—which effective contributions are active within the observation window and when that participation changes. Accessibility-loss events thus represent structurally identifiable transitions in reduced decoherence geometry, independent of microscopic realization.
We identify a regime of open quantum system dynamics in which the observed coherence time exhibits a discontinuous transitionarising from selective loss of accessibility ofan effective decoherence channel. Within theGaussian influence-functional formalism, normalization of the Keldysh weight matrix leadsto a parameter-independent coherence-timeratioR≡ τpostτpre = 43 .The result follows entirely from standardopen-system theory and introduces no modification of quantum mechanics. The predicted transition differs fundamentally fromknowndynamical-decoupling fixed points, occurring in time at fixed control parametersand remaining independent of pulse number.Because the framework yields explicit falsification criteria, the predicted ratio providesa direct experimental probe of multi-channeldecoherence structure. The analysis suggeststhat R = 4/3 represents a structural invariant associated with the normalized geometryof the Keldysh representation.
Dynamical-decoupling spectroscopy using solid-state spin qubits provides a powerful probe of environmental noise across wide frequency ranges. Here we identify a previously unrecognized observable fixed-point behavior in decoherence dynamics arising from additive decoherence channels sampled under narrow-band spectral filtering. We show that the ratio of decoherence times between two experimentally distinguishable configurations converges to a parameter-independent plateau value R ≈ 4/3 over an intermediate range of pulse numbers. This fixed point is independent of microscopic noise models and admits a natural geometric interpretation in terms of decoherence channel structure in the influence-functional description of open quantum systems. A central consequence is a strong experimental prediction: the existence of the plateau requires a band-limited spectral distortion, such that reconstructed noise spectra satisfy S_XY(ω)/S_CPMG(ω) ≈ 4/3 within a finite frequency window while approaching unity outside it. Numerical simulations demonstrate robustness of the effect across realistic noise environments without parameter fine tuning. We further propose an experimentally accessible protocol based solely on standard dynamical-decoupling measurements on a single qubit, enabling direct falsification of the predicted behavior. More broadly, these results indicate that measurement filtering can generate emergent invariant structures in open quantum-system dynamics, suggesting a new organizing principle for interpreting decoherence spectroscopy across quantum sensing platforms. Version 2 (v2) update: This version clarifies the logical structure of the paper by separating the existence of the measurement-induced plateau from the specific benchmark value R=4/3R=4/3R=4/3. The plateau mechanism is presented as a consequence of narrow-band spectral cancellation, while the value R=4/3R=4/3R=4/3 is treated more conservatively as a minimal effective-weight assignment consistent with pulse-sequence symmetry and the numerical results. The revised manuscript also makes the falsifiability structure more explicit and narrows the scope of the numerical claims: the simulations support the existence and robustness of the plateau, but are not presented as a unique microscopic derivation of the effective channel weights. Note (updated): This record corresponds to an earlier exploratory version of the idea. Parts of the theoretical interpretation presented here were not fully established and have been refined in subsequent work. In particular, the universal interpretation of ratio plateaus should be treated with caution. Readers are encouraged to consult the later work (see related records) for a more robust and conservative formulation of the effective description.
Description : This work introduces a novel, model-independent diagnostic framework for quantifying quantum decoherence in primordial inflationary perturbations. The study addresses the fundamental problem of the quantum-to-classical transition in cosmology by defining a normalized persistence functional that captures the suppression of quantum coherence over time. Within an open quantum system approach, each perturbation mode is treated as an effective quantum degree of freedom interacting with an environment, leading to Gaussian suppression of off-diagonal density matrix elements. The proposed functional provides a direct and scalable measure of decoherence efficiency without relying on detailed microscopic modeling. A key feature of the framework is the introduction of a residual coherence parameter, which accounts for possible late-time deviations from complete classicalization. The work further establishes a monotonicity property for the decoherence functional and connects the persistence measure to entropy growth, offering an information-theoretic interpretation of the decoherence process. Importantly, the framework suggests a phenomenological link between residual coherence and observable non-Gaussianity in the cosmic microwave background, opening a pathway for potential observational constraints. The proposed diagnostic functional is broadly applicable across inflationary models and provides a unified tool for comparing decoherence efficiency under different environmental interactions. This work lays the foundation for future studies on quantum signatures in cosmological observables and the persistence of quantum features in the early universe. Keywords : Quantum Decoherence Inflationary Cosmology Primordial Perturbations Open Quantum Systems Quantum-to-Classical Transition Non-Gaussianity Cosmological Perturbation Theory Density Matrix Quantum Cosmology Early Universe Physics Decoherence Functional Entropy and Information Theory
Preprint: This paper derives quantitative bounds on measurement windows for finite-capacity observers extracting information from decohering quantum systems, extending standard decoherence theory to realistic experimental constraints. Main Result: For Gaussian-Markovian decoherence with exponential information decay I(t) = I₀ exp(-2Γt), bounded-capacity observers lose access to system distinctions when mutual information drops below detection threshold ε, yielding measurement window: τ_c = (1/2Γ) log(α C_A / ε) where Γ is decoherence rate [s⁻¹], C_A is observer capacity [bits] defined via Shannon formula (bandwidth × log₂(SNR) × integration time), ε is detection threshold [bits], and α ~ 0.1-1 is a model-dependent constant from spectral decomposition of environmental information. This establishes logarithmic capacity-scaling: doubling detector quality extends measurement windows by only ~0.35/Γ seconds, implying diminishing returns from capacity improvements. Experimental Predictions: For state-of-the-art circuit QED (superconducting transmon qubits, T₁ = 100 μs, bandwidth Δf = 10 MHz, SNR = 10), the framework predicts τ_c ~ 4-10 μs. Varying bandwidth from 1-30 MHz (capacity C_A ∈ [3, 90] bits) produces measurable Δτ_c ≈ 1.7 μs variation (5-10% of coherence time). Five experimental tests discriminate capacity-scaling from standard decoherence: ∙ Tests 1-3: Verify logarithmic capacity-scaling, inverse rate-dependence, threshold-dependence ∙ Test 4: Multi-observer non-redundancy (at most one narrowband detector succeeds) ∙ Test 5: Capacity-dependent redundancy buildup (primary discriminating signature) Key Contributions: ∙ First quantitative analysis of Zurek's pre-objective phase under explicit finite-resource constraints ∙ Capacity-scaling law connecting Shannon information theory to quantum measurement dynamics ∙ Operational definitions ensuring falsifiability (capacity, threshold, mutual information defined via measurement protocols) ∙ Concrete numerical predictions for three platforms (circuit QED, spin qubits, optomechanics) with resource estimates ∙ Design principle: environmental shielding (linear benefit in τ_c) outperforms detector improvement (logarithmic benefit) when both options available Technical Approach: The bound follows from threshold-crossing analysis of exponential decay with capacity-limited initial information I₀ = α C_A, justified via spectral decomposition of environmental information under flat-spectrum approximation for narrowband observation. All parameters (Γ, C_A, ε) are operationally defined and independently measurable, avoiding circularity. Extensions to non-Markovian dynamics (memory kernels), scrambling systems (black holes, many-body chaos), and non-Gaussian noise (Lévy flights, 1/f noise) are discussed with conjectured scaling laws. Scope: The bound applies specifically to Gaussian-Markovian systems (harmonic oscillators, qubits in dispersive limit, weak continuous measurement with memoryless baths). Circuit QED provides optimal testbed due to tunable Purcell filters (bandwidth control), high coherence times (T₁ > 300 μs achieved), and multiplexed readout infrastructure (5+ independent detectors demonstrated). Validity requires α C_A > ε (initial information exceeds threshold); domain violations occur when capacity too small, threshold too high, or coupling too weak. Relation to Prior Work: Zurek's Quantum Darwinism (2003-2009) explains asymptotic objectivity emergence through environmental redundancy but assumes unbounded observers (C_A → ∞, t → ∞). This work analyzes the complementary finite-resource regime (C_A < ∞, t ~ τ_c), providing first capacity-parameterized bound on pre-objective phase duration. Framework is interpretation-neutral—compatible with Copenhagen, Many-Worlds, Bohmian mechanics, and relational quantum mechanics. Philosophical implications (process ontology, observer-dependent reality, impermanence) are explored but clearly separated from testable predictions. Methods: Open quantum systems theory, Shannon information theory, operational quantum measurement, circuit QED experimental physics, numerical prediction for realistic parameters. Content: Complete 90-page manuscript with axiomatic framework (§2), narrowband observation model (§3), main theorem with proof (§4), numerical predictions (§5), five experimental falsification tests (§6), detailed Quantum Darwinism comparison (§7), extensions and limitations (§8), interpretive options (§9), and honest assessment (§10). Includes 77 references and operational definitions for all information-theoretic quantities. Target Audience: Quantum foundations researchers, experimental quantum physicists (circuit QED, trapped ions, quantum dots), quantum information theorists, philosophers of physics interested in measurement and objectivity.
Quantum decoherence—the loss of coherence in a quantum system due to environmental coupling—has been described since the 1980s as a continuous exponential decay of the off-diagonal elements of the density matrix. This mathematical description captures the statistical average of many events, not the underlying mechanism of decoherence itself. Based on the Structural Axiom System (Lin Xiaohei, 2026), this paper proposes: **decoherence is not a continuous, smooth decay, but a discrete process composed of indivisible micro-coupling events.** Each micro-coupling event corresponds to a structural unit—a binary asymmetric relation, the smallest configurational unit—taking shape between system and environment. Each step of decoherence removes one integer share of quantum coherence; macroscopic "gradual decoherence" is the statistical smoothing of many discrete steps. This paper provides: 1. A quantitative formula for the step height: κ = g × d, where g is the micro-coupling strength and d is the structural unit directionality, both independently calibratable. 2. A decomposable verification prediction: changing photon frequency → g changes, but d remains unchanged → the normalized step shape remains invariant. 3. A complete experimental design: single-photon path superposition state + precision environmental coupling + quantum state tomography. If this experiment succeeds, the structural unit will become the first directly observed "configurational quantum"—the empirical confirmation of the smallest unit of existence. This would be the ultimate resolution of the quantum-classical transition problem, comparable in significance to Brownian motion confirming the existence of atoms.
This work introduces a minimal and operational framework for describing decoherence in open quantum systems as a finite-time process. Rather than proposing a new dynamical theory or modifying the axioms of quantum mechanics, the article introduces a bounded, causal, and dimensionless scalar quantity — a local temporal coherence field C(x,t), designed to diagnose the persistence of temporal correlations over a finite causal window. The coherence field is constructed from experimentally accessible observables or reduced-state quantities via a kernel-weighted causal average. It does not represent a new physical degree of freedom and does not introduce additional equations of motion. Instead, it provides a compact diagnostic layer that makes the finite-time structure of coherence explicit, complementing standard descriptions based on memory kernels, time-dependent generators, and Lindblad master equations. The framework is shown to interface naturally with non-Markovian dynamics, coherence-weighted decoherence processes, and effective decay rates, while remaining consistent with standard GKSL structures in the appropriate limits. Its scope, limitations, and relation to existing non-Markovianity measures are explicitly discussed. The coherence-field perspective is intended as an operational and experimentally falsifiable diagnostic tool, applicable across a range of contemporary platforms where finite-time coherence effects are relevant (e.g. superconducting circuits, hybrid light–matter systems, and driven non-equilibrium regimes).This article forms part of the broader Ranesis conceptual framework, which investigates the role of finite-time persistence, coherence, and temporal organization across physical and informational systems. Within that context, the present work constitutes a self-contained and domain-specific application to open quantum systems. No assumptions, postulates, or formal structures from the broader framework are required to read or validate the results presented here.