Active Exploitation of TID Environmental Routing for Key Recovery in Microwave Quantum Channels

This research derives a complete information-theoretic attack chain in whichan adversary actively engineers environmental decoherence modes to exploit thecapacity-weighted routing proposed by the Temporal Information Dynamics (TID)framework for key recovery from a quantum channel. The adversary places a cryo-genic high-Q resonator (thermal occupation ¯n ≈ 0) adjacent to a warm microwavequantum channel (¯n ≫ 1), creating a capacity gradient that, under TID, redirectsinformation from lost photons preferentially toward the adversary’s mode. I computethe per-bit environmental states, verify optimality of the adversary’s measurementvia the Helstrom bound, and derive the mutual information between key bits andadversarial measurements, yielding a Devetak-Winter key rate analysis.A critical finding emerges: the attack is effective only when the quantum biterror rate (QBER) is low. At QBER = 0.5% with 10 dB channel loss, the adversaryextracts 0.328 bits of mutual information per sifted key bit while standard BB84privacy amplification removes only 0.045 bits, yielding 0.283 uncompensated bitsper sifted bit. Paradoxically, higher-quality channels with lower QBER are morevulnerable because reduced privacy amplification leaves less margin against capacity-routed leakage. The crossover occurs at QBER ≈ 6%: below this threshold, theattack breaches security; above it, standard privacy amplification is sufficient.A second critical finding is that this attack surface exists only for microwavequantum communication (superconducting quantum networks), not for standardoptical fibre QKD, because at optical frequencies all environmental modes have¯n ≈ 0 regardless of temperature, eliminating the capacity gradient.All results are conditional on two unproven assumptions: (A1) TID is physicallyvalid and (A2) the decoherence routing basis is the coherent-state basis. The physicalexperiment required to test these assumptions is identified.