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arXiv:2602.02868

Quantum Information Flow in Microtubule Tryptophan Networks

Lea Gassab, Onur Pusuluk, Travis J. A. Craddock

quant-phphysics.bio-phSubmitted Feb 2, 2026• Announced Feb 4, 2026
arXivHTMLPDF

Abstract

Networks of aromatic amino acid residues within microtubules, particularly those formed by tryptophan, may serve as pathways for optical information flow. Ultraviolet excitation dynamics in these networks are typically modeled with effective non-Hermitian Hamiltonians. By extending this approach to a Lindblad master equation that incorporates explicit site geometries and dipole orientations, we track how correlations are generated, routed, and dissipated, while capturing both energy dissipation and information propagation among coupled chromophores. We compare localized injections, fully delocalized preparations, and eigenmode-based initial states. To quantify the emerging quantum-informational structure, we evaluate the $L_1$ norm of coherence, the correlated coherence, and the logarithmic negativity within and between selected chromophore sub-networks. The results reveal a strong dependence of both the direction and persistence of information flow on the type of initial preparation. Superradiant components drive the rapid export of correlations to the environment, whereas subradiant components retain them and slow their leakage. Embedding single tubulin units into larger dimers and spirals reshapes pairwise correlation maps and enables site-selective routing. Scaling to larger ordered lattices strengthens both export and retention channels, whereas static energetic and structural disorder suppresses long-range transport and reduces overall correlation transfer. These findings provide a Lindbladian picture of information flow in cytoskeletal chromophore networks and identify structural and dynamical conditions that transiently preserve nonclassical correlations in microtubules.

Journal reference
Entropy 28(2), 204 (2026)
DOI
10.3390/e28020204

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Networks of aromatic amino acid residues within microtubules, particularly those formed by tryptophan, may serve as pathways for optical information flow. Ultraviolet excitation dynamics in these networks are typically modeled with effective non-Hermitian Hamiltonians. By extending this approach to a Lindblad master equation that incorporates explicit site geometries and dipole orientations, we track how correlations are generated, routed, and dissipated, while capturing both energy dissipation and information propagation among coupled chromophores. We compare localized injections, fully delocalized preparations, and eigenmode-based initial states. To quantify the emerging quantum-informational structure, we evaluate the L1L_1L1​ norm of coherence, the correlated coherence, and the logarithmic negativity within and between selected chromophore sub-networks. The results reveal a strong dependence of both the direction and persistence of information flow on the type of initial preparation. Superradiant components drive the rapid export of correlations to the environment, whereas subradiant components retain them and slow their leakage. Embedding single tubulin units into larger dimers and spirals reshapes pairwise correlation maps and enables site-selective routing. Scaling to larger ordered lattices strengthens both export and retention channels, whereas static energetic and structural disorder suppresses long-range transport and reduces overall correlation transfer. These findings provide a Lindbladian picture of information flow in cytoskeletal chromophore networks and identify structural and dynamical conditions that transiently preserve nonclassical correlations in microtubules.
The hard problem of consciousness, together with the expectation that quantum states should decohere rapidly in the warm and noisy brain, has long challenged quantum approaches to mind, including the orchestrated objective reduction framework. Even so, recent reports of room-temperature superradiance and long-range energy migration in tryptophan networks within microtubules have kept open the possibility that some quantum correlations might be transiently protected in biological settings. In a minimal open XXZ spin-chain model evolved with the Lindblad master equation, stronger nearest-neighbor coupling consistently increased peak transient pairwise entanglement across several topologies and bath conditions. Among the tested environments, the combined bath, which included non-Markovian memory and collective subradiant channels, produced the most favorable balance between entanglement amplitude and coherence lifetime. On a strictly hypothetical Level-C translational reading, these findings suggest two broad intervention levers: increasing effective coupling through cytoskeletal remodeling and reducing per-site dissipation through microtubule stabilization. Within that speculative frame, the Cheung Glutamatergic Regimen is considered as a possible route to the first lever, whereas low-dose lithium orotate and pulsed fisetin are considered as possible routes to the second. Three scheduling frameworks are outlined: daily combined maintenance, cyclic proliferation-consolidation, and baseline stabilization with as-needed plasticity boosts. Testable predictions include changes in gamma-band EEG during insight tasks, altered anesthetic emergence profiles, and shifts in microtubule optical behavior in vitro. This remains a thought experiment only and not medical advice. Any real-world investigation would require formal supervision and stringent safety monitoring because of known risks, including serotonin syndrome.Keywords: quantum biology, microtubule coherence, transient entanglement, glutamatergic plasticity, cognitive enhancement, open quantum systems
Microtubules host dense ultraviolet-absorbing aromatic networks, suggesting an opportunity to engineer their optical response for biotechnology. Here we assess the feasibility of tuning microtubule fluorescence by combining an excitonic radiative-coupling model with molecular-dynamics-derived microtubule-like assemblies and steady-state absorbance and fluorescence measurements in microplate geometries. Simulations quantify how positional and orientational fluctuations reshape radiative rates and quantum yield, and predict how perturbing the tryptophan network by removing a specific site, adding an extra tryptophan at candidate binding pockets, or using mixed modification fractions can modulate emission. Experiments on porcine tubulin dimers and taxol-stabilized microtubules support these trends: polymerization enhances microtubule quantum yield at 280 nm and yields bounded changes at 295 nm due to scattering, while added L-tryptophan reproducibly quenches microtubules at both wavelengths. Together, theory and experiment provide evidence for chemically addressable tuning of microtubule quantum yield and motivate design rules for engineered microtubule photonics.
Quantum approaches to consciousness remain controversial, partly because any putative quantum state in the brain is expected to decohere rapidly in a warm, hydrated, and noisy environment. The present manuscript does not attempt to solve that biological problem directly. Instead, it treats microtubule-related interpretation as a deliberately hypothetical analogy and asks a narrower Level-A question: under what generic open-system conditions can transient pairwise entanglement be enlarged in small noisy XXZ spin chains? In a minimal open XXZ spin-chain model evolved with the Lindblad master equation, stronger nearest-neighbor coupling consistently increased peak transient pairwise entanglement across several topologies and bath conditions. Among the tested environments, the memory-envelope condition gave the longest purity half-life, the collective condition increased late-time purity, and the combined bath is best described as a balanced compromise among selected diagnostics under the chosen parameters rather than as an optimized trade-off. The model is not a physical model of microtubules: it omits full 13-protofilament geometry, dynamic instability, microtubule-associated proteins, hydration structure, ionic screening, and realistic tubulin-scale calibration. On a strictly hypothetical Level-C reading, the two abstract model levers, stronger effective coupling and lower per-site dissipation, may be compared with broad classes of biological perturbation, such as glutamatergic plasticity and cytoskeletal stabilization, but not with named regimens or compounds as clinical routes to enhancement. No dosing schedule, clinical regimen, or cognitive-enhancement recommendation follows from the simulation. The proper experimental sequence is in vitro first, then animal work only if warranted, and human pilot work only after convergent preclinical support and safety review. Testable preclinical predictions include altered tryptophan-network fluorescence lifetimes, exciton migration signatures, superradiance-related optical behavior, and anesthetic sensitivity in controlled preparations. Negative in vitro optical or biophysical results would substantially weaken the biological relevance of the analogy. The manuscript should therefore be read as a reproducible toy-model study with a speculative microtubule analogy, not as evidence that pharmacological modulation can enhance cognition through quantum microtubule effects.
The tryptophan residues in tubulin αβαβαβ-dimers form an ordered aromatic network that has been proposed to support quantum exciton transport even under physiological environmental noise. Existing studies of this system mostly assume white-noise dephasing, but the statistical properties of the protein-solvent bath coupled to tryptophan sites remain uncharacterised under physiological conditions. Here we characterise this fluctuation bath via all-atom molecular dynamics simulations of a solvated tubulin dimer at 310 K, combining high-frequency and long-time trajectories with 10 fs and 10 ps sampling intervals. The resulting autocorrelation of the site-energy fluctuations is tri-exponential, with three well-separated decay modes: sub-100-fs and picosecond fluctuations driven by water dynamics, and a nanosecond mode originating from protein conformational rearrangements. All three modes fall deep within the non-Markovian regime. We further demonstrate that the slow protein mode introduces strong quasi-static disorder, which results in Anderson localisation, while the two fast water modes frequently tune chromophore pairs through resonance, enabling environment-assisted quantum transport (ENAQT). On the full eight-site network, the coloured-noise bath confines excitons predominantly to strongly coupled proximal tryptophan pairs, in marked contrast to the more uniform delocalisation predicted by the standard white-noise Haken-Strobl model. Our workflow generalises to other pigment-protein systems with solvent-exposed chromophores.
We developed a minimal open-quantum-systems pipeline in QuTiP to examine how nearest-neighbor coupling, lattice topology, and multilayer bath structure shape transient entanglement and coherence lifetime in finite XXZ spin chains. The model used N = 4 to 6 qubits evolving under the Lindblad master equation from a product coherent initial state. Four topologies were tested—chain, ring, ladder, and helical_segment—together with five bath variants: local Markovian, Trp_collective, correlated dephasing, non-Markovian memory kernel, and a full combination of all bath layers. Coupling strength J was swept systematically.Across all configurations, stronger J produced a monotonic increase in peak nearest-neighbor concurrence, indicating faster correlation spread before local dissipation took over. Non-Markovian memory kernels and collective subradiant channels provided the strongest protection of coherence, with the memory kernel extending purity half-life most effectively and the collective bath raising late-time purity most strongly. By contrast, adding bonds or increasing N shortened half-life under local noise, consistent with an additive-channel effect. The combined bath gave the best overall balance between transient entanglement and the duration of the coherence window. A parallel classical Kuramoto comparator showed qualitatively similar coupling dependence, suggesting that many observed trends are not uniquely quantum but reflect a broader interaction-versus-noise competition.These results are strictly Level-A findings: numerical outcomes of the Lindblad equation applied to small toy chains with illustrative noise rates. Any mapping to microtubule lattices or to possible pharmacological levers, such as plasticity-driven connectivity changes or microtubule-stabilizing agents, remains hypothetical and is not validated by in vivo evidence. The pipeline is intended as a reproducible computational baseline for isolating mechanistic levers in open quantum networks.
Abstract We examine the quantum coherence properties of tubulin heterodimers arranged into the protofilaments of cytoskeletal microtubules. In the physical model proposed by the authors, the microtubule interiors are treated as high-Q quantum electrodynamics (QED) cavities that can support decoherence-resistant entangled states under physiological conditions, with decoherence times of the order of O(10−6)\mathcal {O}(10^{-6})O(10−6) O ( 10 - 6 ) s. We identify strong electric dipole interactions between tubulin dimers and ordered water dipole quanta within the microtuble interior as the mechanism responsible for the extended coherence times. Classical nonlinear (pseudospin) σ\sigma σ σ -models describing solitonic excitations are reinterpreted as emergent quantum-coherent—or possibly pointer—states, arising from incomplete collapse of dipole-aligned quantum states. These solitons mediate dissipation-free energy transfer along microtubule filaments. We discuss logic-gate-like behaviour facilitated by microtubule-associated proteins, and outline how such structures may enable scalable, ambient-temperature quantum computation, with the fundamental unit of information storage realized as a quDit encoded in the tubulin dipole state. We further describe a process akin to “decision-making” that emerges following an external stimulus, whereby optimal, energy-loss-free signal and information transport pathways are selected across the microtubular network. Finally, we propose experimental approaches—including Rabi-splitting spectroscopy and entangled surface plasmon probes—to validate the use of biomatter as a substrate for scalable quantum computation.