We study multi-qubit quantum channels that can be represented as a product of one-mode fermionic attenuation channels. An explicit formula for the classical capacity $C_1$ and for the minimum output entropy $S_{ min}$ of these channels is proposed. We compute $S_{ min}$ analytically for any number of qubits under assumption that the minimum is achieved on a Gaussian input. Apart from that, a simple numerical method for evaluating $S_{ min}$ is developed. The method is applicable to any channels that are sufficiently noisy. For fermionic product channels the proposed formula for $S_{ min}$ agrees with the numerical results with a precision about $10^{ -9}$.
Categories: quant-ph