A topologically protected quantum dynamo effect in a driven spin-boson model

• Published in: Physical Review A
• Main Authors: Bernhardt, Ephraim, Elouard, Cyril, Hur, Karyn Le, Le Hur, Karyn
• Other Authors: Centre de Physique Théorique Palaiseau (CPHT), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Traitement optimal de l'information avec des dispositifs quantiques (QINFO), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Université Grenoble Alpes (UGA)-Inria Lyon, Institut National de Recherche en Informatique et en Automatique (Inria), ANR-20-ERC9-0010,QSTEAM,Thermodynamique quantique stochastique de l'intrication et de la mesure(2020), ANR-18-CE47-0003,BOCA,Simuler le modèle de Bose-Hubbard dans des circuits supraconducteurs(2018)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: resonance; frequency; oscillator; harmonic; boson; coherence; adiabatic; Hamiltonian; cavity; magnetic field; topological; sphere; pole; Bloch sphere; formation; performance; velocity; spin; electromagnetic field; topology; [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph]; [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]; South pole
• Online Access: https://hal.science/hal-03762951; https://doi.org/10.1103/PhysRevA.107.022219

International audience We describe a quantum dynamo effect in a driven system coupled to a harmonic oscillator describing a cavity mode or to a collection of modes forming an Ohmic bosonic bath. When the system Hamiltonian changes in time, this induces a dynamical field in the bosonic modes having resonant frequencies with the driving velocity. This field opposes the change of the external driving field in a way reminiscent of the Faraday effect in electrodynamics, justifying the term `quantum dynamo effect'. For the specific situation of a periodically driven spin-$\frac{1}{2}$ on the Bloch sphere, we show that the work done by rolling the spin from north to south pole can efficiently be converted into a coherent displacement of the resonant bosonic modes, the effect thus corresponds to a work-to-work conversion and allows to interpret this transmitted energy into the bath as work. We study this effect, its performance and limitations in detail for a driven spin-$\frac{1}{2}$ in the presence of a radial magnetic field addressing a relation with topological systems through the formation of an effective charge in the core of the sphere. We show that the dynamo effect is directly related to the dynamically measured topology of this spin-$\frac{1}{2}$ and thus in the adiabatic limit provides a topologically protected method to convert driving work into a coherent field in the reservoir. The quantum dynamo model is realizable in mesoscopic and atomic systems.