What Are the Biological Limits of Microtubule Quantum Effects?… Establishment of the Coherence Utility Criterion

A new physical benchmark shows that quantum coherence in microtubule tubulin networks cannot plausibly scale up to influence neural activity. Modeling tubulin as an open quantum system at body temperature (310 K) gives coherence times of only 13–39 femtoseconds. To affect millisecond-scale brain functions, the coherence would need amplification of about 100,000-fold, requiring roughly 10⁻⁷ watts of power—five orders of magnitude more than the local GTP energy budget (about 6 × 10⁻¹³ W). The work establishes a reproducible thermodynamic and physical criterion for evaluating future quantum coherence hypotheses in the brain, without endorsing or refuting any specific consciousness model.

Study at a glance

Abstract

A study published on bioRxiv introduces a new "coherence utility" criterion required for quantum coherence phenomena within the tubulin networks of microtubules to connect with macroscopic biological functions. Analyzed using open quantum systems and the Thermodynamic Uncertainty Relation (TUR), the results demonstrate that amplifying femtosecond (fs) level coherence to a neural scale would require immense power, exceeding the local GTP energy budget by about five orders of magnitude (100,000 times). This research is not intended to advocate for a specific model of consciousness, but rather establishes a reproducible physical benchmark to evaluate future quantum coherence hypotheses related to the brain and microtubules within strict thermodynamic and physical limits. [Quantum Biology Society] Quantum effects in living organisms are unavoidable at the molecular scale, but a massive temporal gap exists between microscopic molecular dynamics measured in femtoseconds (quadrillionths of a second) and macroscopic biological functions that take microseconds to milliseconds or longer. Overcoming this gap and revealing how quantum phenomena contribute to biological processes is a long-standing challenge in quantum biology. Recently, a study was published that mathematically identifies the physical conditions required for quantum coherence within the microtubules of neural networks to have actual functional relevance. The paper "Beyond Redfield: Thermodynamic Bounds and Non-Perturbative Quantum Dynamics in Tubulin Networks," published on the preprint repository bioRxiv, presents this critical benchmark. A research team consisting of Facundo Firmenich, Pau Firmenich, and León Firmenich from the Centro de Estudios del Sur (CEDESUR) and the Universitat de Barcelona (UB) conducted this rigorous physical verification. ■ Coherence Utility Criterion for Biological Functions The research team modeled the tubulin network of microtubules as an open quantum system interacting with a warm and wet cellular environment. Simulation results confirmed that at physiological temperature (310 K), the equilibrium quantum coherence time of tubulin is only at the level of 13-39 fs (femtoseconds). The team formulated that for this extremely short microscopic coherence to translate into millisecond-scale neural network functions, it must satisfy the coherence utility condition of U=Kτ_coh/τ_func≥1, which requires an extreme quantum-classical amplification process via an amplification factor (K). ■ Thermodynamic Bounds and Verification of the Quantum Brain Hypothesis In particular, calculations applying the Thermodynamic Uncertainty Relation (TUR) indicate that achieving this neural-scale amplification requires a minimum power of approximately 10⁻⁷ W. This is a massive figure that exceeds the local GTP hydrolysis energy budget available to the microtubule tubulin network (about 6 × 10⁻¹³ W) by more than five orders of magnitude (100,000 times). In other words, they thermodynamically proved that it is difficult to explain the process of microtubule quantum effects converting into macroscopic neural signals using existing equilibrium models or simple amplification mechanisms alone. This research is not aimed at advocating or refuting specific quantum consciousness models, such as Orchestrated Objective Reduction (Orch OR). Rather, its greatest significance lies in establishing an objective and reproducible physical benchmark framework that can verify and evaluate various quantum coherence hypotheses of the brain and microtubules, which may be raised in the field of quantum biology in the future, within strict thermodynamic and physical limits. https://www.biorxiv.org/content/10.64898/2026.05.10.724047v1