Benchmarking Atomic Ionization Driven by Strong Quantum Light

TL;DR

This paper rigorously benchmarks the interaction of strong quantum light with atoms by solving the fully quantized Schrödinger equation, revealing limitations of existing models and proposing a new framework based on Feynman path integrals.

Contribution

It provides the first ab initio simulations of atom-light interaction with bright squeezed vacuum and introduces a novel theoretical approach to include electron-photon entanglement.

Findings

The Q-representation fails to capture the electron-photon joint energy spectrum.

Ab initio simulations reveal limitations of current theoretical models.

A new Feynman path integral framework accurately describes electron-photon entanglement.

Abstract

The recently available high-intensity quantum light pulses provide novel tools for controlling light-matter interactions. However, the rigor of the theoretical frameworks currently used to describe the interaction of strong quantum light with atoms and molecules remains unverified. Here, we establish a rigorous benchmark by solving the fully quantized time-dependent Schr\"{o}dinger equation for an atom exposed to bright squeezed vacuum light. Our \textit{ab initio} simulations reveal a critical limitation of the widely used $Q$-representation: although it accurately reproduces the total photoelectron spectrum after tracing over photon states, it completely fails to capture the electron-photon joint energy spectrum. To overcome this limitation, we develop a general theoretical framework based on the Feynman path integral that properly incorporates the electron-photon quantum entanglement. Our results provide both quantitative benchmarks and fundamental theoretical insights for the emerging field of strong-field quantum optics.