Benjamin Gras

Discovering QKD eavesdropping strategies under asymmetric and time-varying noise entails joint optimisation over discrete attack structure and continuous parameters under a strict evaluation budget. A minimal two-loop search framework, EvoluCMAES, is employed, in which the topology-mutation operator is the only domain-specific component. In BB84, compact eavesdropping circuits of 4--6 gates are consistently identified from an arbitrary-depth search space, approaching the analytical Pauli-channel cloning-machine bound under bit-flip noise. When reformulated as a sequential decision problem, the resulting policy class with feasibility masking and matched hyperparameters recovers the greedy-Oracle strategy for both BB84 and E91/DIQKD. Under soft feasibility, a regime is observed in which a small increase in detection probability yields a statistically significant improvement over the greedy oracle, indicating that budget-limited search exposes nontrivial attack strategies in the presence of noise asymmetry and temporal variation.