The next information technology revolution is the quantum computer, promising a performance boost that exceeds any classical devices by exploiting the quantum properties of physical systems. In our multidisciplinary research we connect different fields and arch across different physical platforms, which is essential for the future application and success of such quantum devices. By combining quantum resource theory from quantum information science, numerical simulations of semiconductor microcavities, and unique quantum-optical experiments, we assess the amount of quantum coherence from the superposition of polaritons, the quasiparticles of a hybrid light-matter system. In contrast to previous methods, such quantum features are studied by measuring photon superpositions in the emitted light, thereby confirming actual quantum coherence -- a potential resource for quantum information processing -- within the generated polariton condensate. This collaborative work was recently published as open access article in PRX Quantum and can be found here.