Semiconductor quantum dots (QDs) have very recently become candidate building blocks of a quantum information technology, after the experimental proof of full single-qubit control. An essential requirement of the quantum information paradigm is the possibility for two qubits to interact coherently in a controlled fashion. Given the recent success in embedding QDs in Photonic Crystal (PHC) devices, photons could provide such a quantum bus, mediating the coherent excitation exchange between two distant dots. Here, we present a comprehensive theoretical analysis of the magnitude and distance dependence of the radiative coupling of two dots in a PHC W1 waveguide, based on Maxwell equations and on the linear excitonic response of the QDs [1].