Nonequilibrium steady state transport of collective-qubit system in strong coupling regime

We investigate the steady state photon transport in a nonequilibrium collective-qubit model. By adopting the noninteracting blip approximation, which is applicable in the strong photon-qubit coupling regime, we describe the essential contribution of indirect qubit-qubit interaction to the population distribution, mediated by the photonic baths. The linear relations of both the optimal flux and noise power with the qubits system size are obtained. Moreover, the inversed power-law style for the finite-size scaling of the optimal photon-qubit coupling strength is exhibited, which is proposed to be universal.