Abstract

We separate information availability from the resources needed to execute recovery in specified finite quantum-radiation models. An energy-labelled three-packet Clifford channel has unrestricted optimal half-diamond recovery error $3(1-p)/4$, where $p$ is the full-transmission probability. Under atomic single-pass delivery of $q$-qubit packets, its even-family optimum at capacity $q$ is $3/4-p/4$, whereas capacity $q+1$ attains unrestricted recovery. A controlled-$Z$ modification has a matching $q$-slot decoder. The reference state is explicitly locally Clifford-equivalent to the Smolin state; its unlocking mechanism is inherited.

We prove a sector-feasibility criterion for energy-preserving isometries and its stronger counterpart for state-independent prescribed probabilities. A repeated emission model has a unique terminal core, coherent vacuum opportunities, internal unitaries, and a loss-closed multiparticle packet space. Its absorption tail is bounded by a binomial tail, and its mean absorption time is at most $K/r_{\ast }$. An explicit collect-and-invert protocol has a complete-channel recovery bound with an event-wise memory ledger. Five ordinary emissions give a prepared-state entropy sequence $0,1,2,2,1,0$, without a terminal drain.

A localized-message transport family gives exact unrestricted recovery and analytically evaluated streaming channels. For inter-emission entangling dynamics, we specify coherent simulation, four complete decoder programmes, numerical semidefinite-program validation, and failure-preserving archival procedures. This computational supplement is not reported as executed: no numerical dynamics result, passing archive, solver certificate, or compilation record is asserted. The proved results are finite-model statements, not a derivation of Hawking radiation, generic scrambling, or gravitational islands.