  Unidirectional light transport in one-dimensional nanomaterials at the
quantum level is a crucial goal to achieve for upcoming computational devices.
We here employ a full-quantum mechanical approach based on master equation to
describe unidirectional light transport through a pair of two-level systems
coupled to a one-dimensional waveguide. By comparing with published
semi-classical results, we find that the nonlinearity of the system is reduced,
thereby reducing also the unidirectional light transport efficiency. Albeit not
fully efficient, we find that the considered quantum system can work as a light
diode with an efficiency of approximately 60%. Our results may be used in
quantum computation with classical and quantized light.
