Quantum objects, sometimes called quantons, often display a characteristic feature that is referred to as wave-particle duality (WPD). Lately, this and other quantum traits have been submitted to intensive research, mainly motivated by the development of quantum information science. As a consequence, the scope of some concepts have been extended and it has been realized that they are not in the exclusive domain of quantum physics. This is particularly clear in optics, where qubits may show up as Jones vectors and WPD has its counterpart as wave-ray duality. WPD was originally addressed by focussing on a single qubit, which was afterwards supplemented with a second one playing the role of a path-marker in an interferometric setup. Fringe contrast, a sign of wavelike behavior, was proved to be diminished in connection with the e ectiveness of the marker, the inducer of particle-like behavi...