Phase-Load--Saturating QKD: Basin Exhaustion as a Security Primitive

We propose a quantum key distribution (QKD) paradigm in which security derives from phase-space capacity exhaustion rather than basis secrecy or computational hardness. Building on attractor-dominated dynamics observed in driven quantum systems, we introduce Phase-Load--Saturating QKD (PLS-QKD): Alice intentionally occupies the tangential degrees of freedom of the signal manifold up to a calibrated capacity, so that any additional coherent coupling by an eavesdropper (Eve)---including tangential, weak, or deferred-measurement attacks---forces the system out of the admissible basin. Bob detects security violations as macroscopic loss of locking rather than small error-rate increases. We formalize the threat model, define security via basin exclusion, and sketch concrete photonic and continuous-variable realizations. This approach offers a phase-space--native route to quantum security and addresses coherent, tangential attacks that evade standard QKD assumptions.