Cuevas, ÁlvaroLópez Carreño, Juan CamiloSilva, BlancaDe Giorgi, MilenaSuárez-Forero, Daniel GSánchez Muñoz, CarlosFieramosca, AntonioCardano, FilippoMarrucci, LorenzoTasco, VittoriannaBiasiol, Giorgiodel Valle, ElenaDominici, LorenzoBallarini, DarioGigli, GiuseppeMataloni, PaoloLaussy, Fabrice PSciarrino, FabioSanvitto, Daniele2018-09-252018-09-252018-04-20Cuevas, Á, Carreño, JCL, Silva, B, De Giorgi, M, Suárez-Forero, DG, Muñoz, CS, Fieramosca, A, Cardano, F, Marrucci, L, Tasco, V, Biasiol, G, Del Valle, E, Dominici, L, Ballarini, D, Gigli, G, Mataloni, P, Laussy, FP, Sciarrino, F, Sanvitto, D. (2018) 'First observation of the quantized exciton-polariton field and effect of interactions on a single polariton', Science Advances, 4 (4) eaao6814 doi: 10.1126/sciadv.aao68142375-25482972561610.1126/sciadv.aao6814http://hdl.handle.net/2436/621715© 2018 The Authors. Published by Science. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1126/sciadv.aao6814Polaritons are quasi-particles that originate from the coupling of light with matter and that demonstrate quantum phenomena at the many-particle mesoscopic level, such as Bose-Einstein condensation and superfluidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behavior has remained fully accounted for by classical and mean-field theories. We report the first experimental demonstration of a genuinely quantum state of the microcavity polariton field, by swapping a photon for a polariton in a two-photon entangled state generated by parametric downconversion. When bringing this single-polariton quantum state in contact with a polariton condensate, we observe a disentangling with the external photon. This manifestation of a polariton quantum state involving a single quantum unlocks new possibilities for quantum information processing with interacting bosons.application/PDFenQuantum physicspolaritonsentanglementquantum technologyJournal articleScience Advanceseaao6814