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Structured dephasing from a massive scalar memory field: exact treatment, model-selection pitfalls, exclusion limits, and two kinematic signatures

Enrico Maresca

Published Aug 23, 2026• 0 citations
Publisher

Abstract

Structured dephasing from a massive scalar memory field What this is -> A model of quantum decoherence, and the record of what happenedwhen it was tested against itself. An earlier version of this work proposed that a qubit's loss of coherence isshaped by an auxiliary scalar field acting as an "informational memory", andreported that an oscillatory decay law fitted simulated data far better than thestandard exponential and stretched-exponential laws. This version retracts thatevidence and reports what survives. What went wrong -> The statistical advantage was an artefact. The simulated databegan at a coherence value above 1 — physically impossible — which no admissiblecompeting model could follow. Once the coherence function is correctlynormalised, the proposed law drops from first to fourth place. Worse, datagenerated by an ordinary structured boson bath, containing no memory field of anykind, are fitted equally well by the same law. Goodness of fit cannot tell the twoapart. Fitted oscillation frequencies are biased estimators of the field mass byroughly 50%. What else failed -> Memory measures do not single the field out either. Atmatched decoherence, an ordinary narrow Lorentzian pseudomode is thirteen timesmore non-Markovian than the field. And the system–field mutual information turnsout to be a function of the coherence alone, for *every* dephasing environment —measuring it is measuring the coherence again in different units. The"informational" reading is not supported and has been dropped. Whether it was already dead -> If the field were fundamental and coupled tomatter density, a spectral threshold in the GHz band would require a Compton rangeof centimetres, exactly where torsion-balance experiments are most sensitive. Aqubit's differential charge under such a coupling — the two states contain the sameatoms and differ only by the transition energy — falls short of observability byabout 35 orders of magnitude. As new fundamental physics, the model is excludedoutright. What survives, and it is testable -> Read instead as an effective mode of thedevice's own environment — a phonon branch, a packaging mode, a structureddefect bath — the model needs no new physics and makes two sharp predictions.The noise spectrum acquires a hard threshold with a square-root edge, absent insmooth Lorentzian environments and resolvable by CPMG noise spectroscopy at the 1%level. And for two qubits at separation *r*, the cross-spectrum is the self-spectrummodulated by sinc(*kr*), whose zeros overdetermine the band edge and theseparation, and whose correlation reverses sign with distance — exchanging whichBell state is protected. Ordinary crosstalk is monotonic in separation and cannotreverse. Why it may be worth reading anyway. -> The methodological lesson generalises wellbeyond this model: in non-Markovian decoherence, fit quality is close to worthlessas evidence, because too many physically different environments produce the samecurve. What discriminates is structure — thresholds, zeros, sign changes — notgoodness of fit. The three admissibility constraints derived here (boundedcoherence, quadratic short-time onset, and the plateau implied by a spectral gap)are cheap to apply and reject most published fitting forms. All numerical results are reproducible: code, seeds, figures and a verificationsuite are included. Status: preprint, not peer reviewed. All data are simulated; nothing hereestablishes that the predicted signatures exist in any real device. The paperstates what would have to be observed, and what would have to be excluded, forthem to count.

DOI
10.5281/zenodo.22062675

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Structured dephasing from a massive scalar memory field What this is -> A model of quantum decoherence, and the record of what happenedwhen it was tested against itself. An earlier version of this work proposed that a qubit's loss of coherence isshaped by an auxiliary scalar field acting as an "informational memory", andreported that an oscillatory decay law fitted simulated data far better than thestandard exponential and stretched-exponential laws. This version retracts thatevidence and reports what survives. What went wrong -> The statistical advantage was an artefact. The simulated databegan at a coherence value above 1 — physically impossible — which no admissiblecompeting model could follow. Once the coherence function is correctlynormalised, the proposed law drops from first to fourth place. Worse, datagenerated by an ordinary structured boson bath, containing no memory field of anykind, are fitted equally well by the same law. Goodness of fit cannot tell the twoapart. Fitted oscillation frequencies are biased estimators of the field mass byroughly 50%. What else failed -> Memory measures do not single the field out either. Atmatched decoherence, an ordinary narrow Lorentzian pseudomode is thirteen timesmore non-Markovian than the field. And the system–field mutual information turnsout to be a function of the coherence alone, for every dephasing environment —measuring it is measuring the coherence again in different units. The"informational" reading is not supported and has been dropped. Whether it was already dead -> If the field were fundamental and coupled tomatter density, a spectral threshold in the GHz band would require a Compton rangeof centimetres, exactly where torsion-balance experiments are most sensitive. Aqubit's differential charge under such a coupling — the two states contain the sameatoms and differ only by the transition energy — falls short of observability byabout 35 orders of magnitude. As new fundamental physics, the model is excludedoutright. What survives, and it is testable -> Read instead as an effective mode of thedevice's own environment — a phonon branch, a packaging mode, a structureddefect bath — the model needs no new physics and makes two sharp predictions.The noise spectrum acquires a hard threshold with a square-root edge, absent insmooth Lorentzian environments and resolvable by CPMG noise spectroscopy at the 1%level. And for two qubits at separation r, the cross-spectrum is the self-spectrummodulated by sinc(kr), whose zeros overdetermine the band edge and theseparation, and whose correlation reverses sign with distance — exchanging whichBell state is protected. Ordinary crosstalk is monotonic in separation and cannotreverse. Why it may be worth reading anyway. -> The methodological lesson generalises wellbeyond this model: in non-Markovian decoherence, fit quality is close to worthlessas evidence, because too many physically different environments produce the samecurve. What discriminates is structure — thresholds, zeros, sign changes — notgoodness of fit. The three admissibility constraints derived here (boundedcoherence, quadratic short-time onset, and the plateau implied by a spectral gap)are cheap to apply and reject most published fitting forms. All numerical results are reproducible: code, seeds, figures and a verificationsuite are included. Status: preprint, not peer reviewed. All data are simulated; nothing hereestablishes that the predicted signatures exist in any real device. The paperstates what would have to be observed, and what would have to be excluded, forthem to count.
We propose an effective field-theoretic framework for open quantum systems in which decoherence dynamics are influenced by an auxiliary scalar field acting as an informational memory degree of freedom. This additional field induces intrinsically non-Markovian behavior, leading to structured noise spectra and deviations from standard exponential decay. The resulting reduced dynamics are governed by a non-local memory kernel, capturing temporal correlations beyond conventional approaches. We show that the model predicts oscillatory modulations in coherence decay and provides improved fits to simulated qubit data compared to both exponential and stretched-exponential models. The framework also reproduces nontrivial residual structures and spectral features that are not accounted for in standard decoherence theories. To test these predictions, we propose an experimental protocol using superconducting qubits, where systems initialized under identical environmental conditions but with different controlled histories exhibit distinguishable decoherence dynamics. This history dependence offers a potential experimental signature of the proposed mechanism. Overall, this work provides a phenomenological extension of decoherence theory and highlights the role of memory effects and informational degrees of freedom in open quantum systems, suggesting new directions for both theoretical and experimental investigation.
I propose a mechanism for actively suppressing quantum decoherence by engineering a structuredspin environment that modifies the propagation of environmental fluctuations. Unlike conventionalapproaches that attempt to decouple the qubit from its surroundings, my framework leverages thesame spin-boson interaction responsible for decoherence to reshape the noise spectrum at its origin.Using an effective field theory description, I show that a dense, correlated spin shell generates aself-energy correction to a coupled bosonic mode (e.g., phonons or magnons), producing an emergentmass gap and exponential attenuation of fluctuations within a characteristic length δ ∼ 1/√nSχS.I derive the resulting enhancement of coherence time T2, validate the mechanism with numericalsimulations including 1/f, white, and spin-bath noise, and identify an optimal density regime nS ∼1019–1020 cm−3 where net protection occurs. The enhancement is non-monotonic, reaching factorsof 5–15 under realistic conditions.A decisive experimental signature is the ordering:Tordered2 > T bare2 > T disordered2which cannot be explained by conventional uncorrelated spin-bath models.
Directed Recoherence in Structured Non-Markovian Environments presents a rigorously defined operating regime of open quantum system dynamics in which environmental memory leads not to oscillatory revivals, but to directed, monotonic recoherence toward a long-lived metastable coherence plateau. The work introduces a minimal and physically standard two-bath pure-dephasing model composed of a broadband Markovian noise bath and a narrowband non-Markovian reference bath. Within this framework, a dimensionless recoherence parameter R = λ_R² / [ γ_N Γ (1 + (δ/Γ)² ) ] is shown to govern a sharp transition between ordinary decoherence and a directed recoherence regime. When R exceeds a threshold of order unity, the system exhibits a single coherence minimum followed by monotonic recoherence and a metastable phase-locked plateau over experimentally relevant timescales. Exact closed-form solutions for the coherence dynamics are derived, alongside falsifiable predictions including bounded phase deviation relative to the reference bath. Numerical simulations confirm the existence of a critical threshold and distinguish this regime from known non-Markovian revivals, decoherence-free subspaces, driven steady states, and many-body prethermalization. The manuscript reframes Self-Initiated Phase Re-Coherence (SIPR) not as a new physical principle, but as a previously under-characterized regime within standard quantum open-system theory. Potential experimental realizations are discussed for superconducting qubits with Purcell-filtered environments and trapped ions with engineered sidebands. A companion conceptual document explores the epistemic and interpretational implications of measurement, observation, and environmental structure without modifying the physical results presented here.
Record-Conditioned Reduction and the Decoherence Cliff This paper proposes a falsifiable reconstruction-based account of quantum measurement. Its central claim is that the loss of interference is not merely a smooth Markovian decay, but a first-passage phenomenon: coherence persists until a reconstructive admissibility threshold is crossed. Purpose Building on the causal-segment structure of Article 19, the paper interprets measurement as the moment when a coherent reconstruction can no longer remain admissible because the record has accumulated enough information to distinguish the branches. Main Idea A superposition remains reconstructively admissible while the branch information is below a threshold. Once the accumulated record crosses that boundary, the coherent segment closes and the system undergoes record-conditioned reduction. The Decoherence Cliff The visibility of interference is identified with the survival probability of a first-passage process. This predicts a characteristic “cliff”: a sharp loss of visibility around a critical number of elementary causal steps. The cliff location is governed by: Nc = Iadm / Îmut where Îmut is the per-step mutual Fisher information and Iadm is the total admissibility threshold. Empirical Content The model predicts a threshold law rather than a simple exponential decay. Its distinctive signature is a sharp transition whose location scales with the coherence window, together with a Fano-factor structure different from ordinary Markovian decoherence. Relation to Decision Theory The admissibility threshold is later identified with the branch entropy H(p), giving Iadm = ln 2 for a balanced superposition. This turns the cliff location into a parameter-free prediction in the ideal pure-branch case. Status The paper is a preprint-level proposal in the foundations of quantum mechanics. Its strongest content is the falsifiable replacement of smooth decoherence by a first-passage admissibility threshold. Its remaining burden is to establish the strong impossibility result against signed-increment or hidden Markovian reformulations. Conclusion This paper reframes measurement as the crossing of a reconstructive admissibility boundary. If correct, reduction is not an added postulate but the observable cliff produced when a coherent causal segment ceases to be globally admissible.
Decoherence is often modeled using Markovian master equations that predict exponential suppression of coherence and are frequently used as effective bounds on quantum behavior in complex environments. Such descriptions, however, correspond to the singular physical limit of vanishing environmental memory. Here we formulate decoherence using a general time-nonlocal decoherence functional determined solely by the environmental force correlation function, with Markovian dynamics recovered explicitly as a limiting case. For arbitrary stationary environments with finite temporal correlations, we show that the decoherence functional exhibits quadratic short-time growth that is model-independent within the finite-memory class considered. Consequently, the decoherence time defined operationally-without assuming exponential decay-scales as the square root of the environmental correlation time, independent of the detailed form of the bath correlation kernel. These results are illustrated analytically for Gaussian-correlated, soft power-law, and Ornstein-Uhlenbeck environments. In the Ornstein-Uhlenbeck case, the non-Markovian dynamics admit an exact analytical closure, yielding a closed evolution equation for the coherence. Exact numerical simulations based on a pseudomode mapping confirm the predicted scaling and show that exponential decoherence emerges only in the memoryless limit. Beyond coherence decay, we distinguish decoherence rates from observable loss of quantum signatures by analyzing purity and von Neumann entropy dynamics. We show that suppression of a specific coherence element need not coincide with irreversible entropy production. Finally, we introduce an inferred-memory perspective in which the environmental correlation time is treated as an operationally extractable parameter from dynamical data.