Relativistic quantum communication: Energy cost and channel capacities

We consider the communication of classical and quantum information between two arbitrary observers in asymptotically flat spacetimes (possibly containing black holes) investigate what is energy cost for such transmission. By means localized two-level systems, sender receiver can use a scalar field as channel. As we have already shown previous paper, channel has non-vanishing capacity well entanglement-assisted capacities. Here will show that change expectation value system during process be separated in: (i) contribution coming from particle creation due to spacetime, (ii) associated with needed switch-on/off each qubit, {\bf (iii)} term which comes itself. For considered here, extra vanishes. result, if one created qubits some specific task (e.g., computation) also reliably convey its parts no cost. conclude paper by illustrating form capacities contributions paradigmatic cases Minkowski spacetime: (1) inertial motion (2) while uniformly accelerated.