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- Title
Connecting nth order generalised quantum Rabi models: Emergence of nonlinear spin-boson coupling via spin rotations.
- Authors
Casanova, Jorge; Puebla, Ricardo; Moya-Cessa, Hector; Plenio, Martin B.
- Abstract
We establish an approximate equivalence between a generalised quantum Rabi model and its nth order counterparts, where spin-boson interactions are nonlinear as they comprise a simultaneous exchange of n bosonic excitations. Although there exists no unitary transformation between these models, we demonstrate their equivalence to a good approximation in a wide range of parameters. This shows that nonlinear spin-boson couplings, i.e., nth order quantum Rabi models, are accessible to quantum systems with only linear coupling between boson and spin modes by simply adding spin rotations and after an appropriate transformation. Furthermore, our result prompts novel approximate analytical solutions to the dynamics of the quantum Rabi model in the ultrastrong coupling regime improving previous approaches. Modelling light-matter coupling: a linear key to nonlinear interactions Dynamics of nonlinearly-interacting light-matter systems can be described using just linear terms and spin rotations. An international team of researchers, led by Jorge Casanova at the University of Ulm, managed to draw a connection between a generic model involving nonlinear interactions (i.e., emission/absorption of many photons at the same time from the same particle) with a simpler model involving just linear terms and spin rotation. This connection allows them to approximately simulate the dynamics of nonlinearly-interacting systems without actually including nonlinearities. Models such as the ones studied here describe many disparate quantum systems, and are thus both of fundamental and technological interest; in particular, the authors' discovery would imply that quantum simulation of nonlinearly-interacting system can be performed also in systems lacking actual nonlinear spin-boson coupling.
- Publication
NPJ Quantum Information, 2018, Vol 4, Issue 1, pN.PAG
- ISSN
2056-6387
- Publication type
Article
- DOI
10.1038/s41534-018-0096-9