Information and physics are closely and fascinatingly intertwined. Their relations become even more interesting when we leave a non-relativistic quantum mechanics for more exiting venues. My notes are planned as a guided tour for the first steps along that road, and at the same time as an illustration of the basic notions of quantum information theory in more exotic settings. I start from a brief introduction to causality restrictions on the distributed measurements: the limitations that are imposed by final propagation velocity of the physical interactions. It is followed by the relativistic transformations of the states of massive particles and photons, from which we can deduce what happens to qubits which are realized as the discrete degrees of freedom. Building on this, I discuss the distinguishability of quantum signals, and briefly touch communication channels and the bipartite entanglement. Creation of the entanglement in scattering processes will be touched only briefly, while the fascinating experimental results on the entanglement in particle physics are discussed in the contribution by Beatrix Hiesmayr.