Speaker: Ricardo Puebla Antunes
Affiliation: Centre for Theoretical Atomic, Molecular, and Optical Physics, School of Mathematics and Physics, Queen’s University Belfast, Belfast (UK)
Date: Tuesday, 18 December 2018 at 15:30
Location: Seminar Room, Serrano 121 (CFMAC)
The interaction between a spin-1/2 particle and a bosonic mode is one of the most fundamental models in quantum mechanics and in the description of light-matter systems. In particular, when the interaction between the subsystems comprises a linear exchange of quantum excitations, that is, when the spin state changes by absorbing or emitting only one bosonic excitation, the model is known as quantum Rabi model. This celebrated model is of paramount importance not only for a comprehensive description of light-matter interaction, but also because it describes different physical systems such as trapped ions or circuit QED, and it has thus become a milestone in the development of quantum-based technologies and quantum information processing [1]. There are yet other possible interaction mechanisms between a spin-1/2 particle and a bosonic mode beyond the linear case. For example, it may be possible that the spin state changes at the expense of emitting or absorbing n>1 bosonic excitations. Such a multiphoton interaction dramatically modifies the system’s properties with respect to its linear counterpart, and thus the features of a light-matter interacting system. Although there is no unitary transformation between linear and multiphoton quantum Rabi models, it has been shown that their dynamics are equivalent to a very good approximation in a wide range of parameters [2], also including models featuring spin-boson coupling that changes with the Fock occupation number [3].
Here, I will describe the theoretical framework which allows us to find an approximate equivalence among a family of quantum Rabi models, which holds even in the presence of decoherence processes [3], and provide relevant examples of the equivalence. In particular, our work implies that quantum simulation of multiphoton and nonlinearly-interacting system can be performed also in systems lacking actual multiphoton and nonlinear spin-boson coupling. As these multiphoton and nonlinear models are typically hard to control or even to implement, our work opens new avenues for the simulation and exploration of a large class of fundamentally different quantum models, allowing as well for the inspection of distinct dissipative processes.
[1] D. Braak et al. J. Phys. A: Math. Theor. 49, 300301 (2016); E. Solano Physics 4, 68 (2011)
[2] J. Casanova et al. npj Quantum Information 4, 47 (2018)
[3] R. Puebla et al. arxiv:1810.08465