  With the rapid deployment of quantum computers and quantum satellites, there
is a pressing need to design and deploy quantum and hybrid classical-quantum
networks capable of exchanging classical information. In this context, we
conduct the foundational study on the impact of a mixture of classical and
quantum noise on an arbitrary quantum channel carrying classical information.
The rationale behind considering such mixed noise is that quantum noise can
arise from different entanglement and discord in quantum transmission
scenarios, like different memories and repeater technologies, while classical
noise can arise from the coexistence with the classical signal. Towards this
end, we derive the distribution of the mixed noise from a classical system's
perspective, and formulate the achievable channel capacity over an arbitrary
distributed quantum channel in presence of the mixed noise. Numerical results
demonstrate that capacity increases with the increase in the number of photons
per usage.
