Photon pumping in a weakly-driven quantum cavity-spin system

TL;DR

This paper demonstrates a novel photon pumping effect in a driven quantum cavity-spin system, showing high efficiency and robustness of frequency conversion even outside the adiabatic regime, with implications for quantum coherence preservation.

Contribution

It reveals a new photon pumping phenomenon in a nonadiabatic regime and links it to Floquet state delocalization and multifractality, expanding understanding of quantum cavity-spin dynamics.

Findings

Photon frequency conversion efficiency up to 80%.

Pumping persists in nonadiabatic, weak, and strong drive regimes.

Floquet states exhibit multifractal delocalization.

Abstract

We investigate the photon pumping effect in a topological model consisting of a periodically driven spin-1/2 coupled to a quantum cavity mode out of the adiabatic limit. In the strong-drive adiabatic limit, a quantized frequency conversion of photons is expected as the temporal analog of the Hall current. We numerically establish a novel photon pumping phenomenon in the experimentally accessible nonadiabatic driving regime for a broad region of the parameter space. The photon frequency conversion efficiency exhibits strong fluctuations and high efficiency that can reach up 80% of the quantized value for commensurate frequency combinations. We link the pumping properties to the delocalization of the corresponding Floquet states which display multifractal behavior as the result of hybridization between localized and delocalized sectors. Finally we demonstrate that the quantum coherence properties of the initial state are preserved during the frequency conversion process in both the strong and ultra-weak-drive limit.