doi:10.1103/PhysRevA.99.013807engZueco, D.García-Ripoll, J.Ultrastrongly dissipative quantum Rabi modelART-2019-110400We discuss both the spectrum and the dynamics of cavity QED in the presence of dissipation beyond the standard perturbative treatment of losses. Using the dynamical polaron ansatz and matrix-product state simulations, we discuss the case where both light-matter g coupling and system-bath interaction are in the ultra-strong-coupling regime. We provide a critical g for the onset of Rabi oscillations. Besides, we demonstrate that the qubit is dressed by the cavity and dissipation. Such a dressing governs the dynamics and, thus, it can be measured. Finally, we sketch an implementation for our theoretical ideas within circuit QED technology.2019http://zaguan.unizar.es/record/7718110.1103/PhysRevA.99.013807http://zaguan.unizar.es/record/77181oai:zaguan.unizar.es:77181info:eu-repo/grantAgreement/ES/DGA/CAM PRICYT/QUITEMAD+S2013-CE-2801info:eu-repo/grantAgreement/ES/DGA/Q-MADinfo:eu-repo/grantAgreement/ES/MINECO/FIS2015-70856-Pinfo:eu-repo/grantAgreement/ES/MINECO/MAT2017-88358-C3-1-Rinfo:eu-repo/grantAgreement/EUR/QUANTERA/SUMOPhysical Review A 99, 1 (2019), 013807 [11 pp]All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess