Toward a Quantum-Acoustic Human-Plant Communication Loop: Integrating Radical-Pair Magnetoreception, Ultrasonic Clicks, and Vagal Neurofeedback

Plants emit ultrasonic clicks (20-80 kHz) under abiotic stress, while their cryptochrome (CRY1/2) flavoproteins host spin-correlated radical pairs sensitive to geomagnetic-scale fields. Humans, in turn, exhibit vagally mediated heart-rate variability (HRV) shifts when presented with low-frequency rhythmic audio and auricular tVNS. We propose a quantum-acoustic feedback loop: (i) plant radical-pair phase biases xylem cavitation dynamics, altering click burst statistics; (ii) clicks are down-mixed and amplitude-modulated to entrain human HRV via an ear-mounted tVNS headset; (iii) human responses modulate blue-light phase delivered to leaves, closing the loop. We formalise the coupling with a two-channel Hamiltonian, derive an entropy-exchange relation, and outline a three-phase experimental protocol.