The Brain Performs Quantum Computation with Nuclear Spins... The Posner Molecule Hypothesis

Abstract

A study published in Annals of Physics (with an initial draft available on arXiv) proposes a new operational framework for a "nuclear spin quantum brain" that is distinct from the existing microtubule model. The research identifies "Posner molecules" (Ca₉(PO₄)₆), which are calcium phosphate clusters in body fluids, as a unique molecule that protects the nuclear spins of phosphorus (P) atoms from thermal and chemical disturbances, acting as a natural shield for neural qubits. It demonstrates that quantum entanglement states generated within Posner molecules can be preserved for minutes to hours (up to approximately one day), potentially enabling non-local brain synchronization and driving cognitive functions across neurons. [Quantum Biology Society] How exactly the human brain forms consciousness and performs advanced cognitive functions has long remained one of science's most profound mysteries. To explain the quantum actions of neural networks, the microtubule model proposed by Roger Penrose and others has been widely known. Recently, however, a new hypothesis has been proposed—using a completely different approach—suggesting that the brain processes quantum information (qubits) using the nuclear spins of specific molecules, attracting significant attention from the scientific community. The paper "Quantum Cognition: The possibility of processing with nuclear spins in the brain," authored solely by Professor Matthew P. A. Fisher of the Department of Physics at the University of California, Santa Barbara (UC Santa Barbara), presents this revolutionary framework for a nuclear spin-based quantum brain. ■ Posner Molecules: A Natural Protective Shield for Quantum Qubits The biggest challenge for quantum computation is that quantum coherence is easily destroyed by chemical and thermal disturbances in the warm, wet biological environment. Professor Fisher identified the "Posner molecule" (Ca₉(PO₄)₆), a calcium phosphate cluster commonly present in body fluids, as nature's solution to this problem. Physical analysis revealed that these Posner molecules act as a natural shield for neural qubits, thoroughly isolating the nuclear spins of phosphorus (P) atoms from electrical and magnetic disturbances in the external environment. ■ Quantum Entanglement Maintained for Hours Thanks to this robust protection, the quantum entanglement of phosphorus nuclear spins within Posner molecules remains intact for significantly longer than in typical quantum systems. According to the research calculations, due to the rapid rotation of Posner molecules in aqueous solution, dipole magnetic fields are averaged and canceled out, allowing the coherence time (t_coh) of this entanglement to be preserved for minutes or even up to a day (10⁵ seconds). This provides sufficient working memory time for quantum information to be meaningfully stored and processed on a neurophysiological timescale. ■ Non-local Brain Synchronization Across Neural Networks Furthermore, multiple Posner molecules that maintain an entangled state can freely enter presynaptic neurons through mechanisms such as vesicle endocytosis. As these entangled Posner molecules, distributed across various neurons, chemically bind and subsequently melt, they release a shower of calcium ions, triggering further neurotransmitter release. This enables multiple neurons to achieve non-local biochemical synchronization. In other words, it strongly suggests that Posner molecules could ultimately drive the complex computations and cognitive functions of the brain, providing an entirely new biophysical insight into the origins of consciousness and cognitive processes. https://arxiv.org/abs/1508.05929