Quantum Key Distribution in Multi-Valued Logic: Using Entangled Qutrits for Unconditional Security

This paper presents two novel quantum key distribution (QKD) protocols operating in three-valued (qutrit-based) logic. Protocol I demonstrates a simplified QKD scheme that avoids quantum qubit transmission, relying instead on entangled qutrit pairs to achieve unconditional security between one sender and one receiver. Protocol II generalises this framework to n = 3ᵐ receivers using a maximally entangled (m+n) -qutrit state. The key efficiency η = (n+1) / (n+m) exceeds 50% and improves with the number of users. Both protocols achieve unconditional security. This work constitutes the first reported QKD protocol designed natively for three-valued quantum logic.