The Effect of Intense Light on the Energy Levels of Atoms

Dmitriy V. Kupriyanov, Igor M. Sokolov

We examine the optical pumping effect in an ensemble of three-level atoms with a Λ configuration of the energy sublevels excited by parametric luminescence light in the squeezed state. We derive quantum kinetic equations that describe the evolution of the density matrix of atoms irradiated by low-intensity squeezed light with a finite-width spectrum. In particular, we show that because of the quantum statistical properties of the squeezed light there can be a redistribution of atoms among the lower energy sublevels, despite the equality of the intensities of the spectral components of the light that resonantly excites optical transitions in the Λ-system. The relation of the optical pumping effect to the correlation and spatial-temporal spectral properties of squeezed light is discussed in detail. Finally, we show that the effects are closely linked to the finiteness of the width of the squeezed-light spectrum.

Crispin W. Gardiner

Sylvain Nascimbène, Jean Dalibard

An optical flux lattice is a set of light beams that couple different internal states of an atom, thereby producing topological energy bands. Here we present a configuration in which the atoms exhibit a dark state, i.e., an internal state that is not coupled to the light. At large light intensity, the low-energy dynamics is restricted to the dark state, leading to an effective continuum model with a Landau-level-like structure. This structure is dramatically different from that of usual topological optical lattices, which lead to discrete models in the tight-binding limit. For well-chosen atomic species, the proposed system is essentially immune to heating due to photon scattering, making it a highly promising way to emulate the integer or fractional quantum Hall effect.

Zhejun Jiang, Shengzhe Pan, Jianqi Chen +12 more

Nonlinear optical processes, mediated by multiphoton interactions rather than single-photon response, are routinely exploited to enable a range of light-based functionalities in devices and applications. Nonlinear effects are enhanced through higher intensity fields, which is a limiting strategy owing to potential radiation damage. An alternative strategy relies on the fluctuation redistribution typical of quantum light, but experimental demonstrations at the most fundamental level have been limited. Here we report experimental nonlinear tunnelling ionization of isolated atoms, a pivotal nonlinear process that drives high-harmonic generation and forms the basis of attosecond science, boosted by quantum light -- bright squeezed vacuum (BSV). A BSV light with an average pulse energy of 300 nJ achieves an effective intensity equivalent to that of a coherent light with 7.1 {\textmu}J, demonstrating a more than 20-fold quantum boost in nonlinear effect from BSV light. This boost is revealed by matching the peaks of the photoelectron momentum spectra produced by the BSV and coherent light using angular streaking. Furthermore, we demonstrate control of the effective intensity of the BSV by tuning the correlation function at fixed average pulse energy, establishing a robust method to tailor nonlinear processes via quantum statistics rather than classical intensity scaling. These findings may facilitate the development of quantum-controlled strong-field dynamics using tailored quantum light sources.

Crispin W. Gardiner, P. Zoller