Squeezed states of light after high-harmonic generation in excited atomic systems

TL;DR

This paper theoretically explores how high-harmonic generation in excited atomic systems can produce non-classical light states, including significant squeezing and entanglement, enabling the creation of optical Schrödinger kitten states.

Contribution

It introduces a novel theoretical analysis of squeezed and entangled light states generated via HHG in excited atoms, including heralded Schrödinger kitten states.

Findings

Significant single-mode squeezing observed in driving and harmonic modes

Two-mode squeezing features identified between fundamental and harmonic modes

Generation of optical Schrödinger kitten states through heralding measurements

Abstract

High-harmonic generation (HHG) has recently emerged as a promising method for generating non-classical states of light with frequencies spanning from the infrared up to the extreme ultraviolet regime. In this work, we theoretically investigate the generation of squeezed states of light through HHG processes in atomic systems that had been initially driven to their first excited state. Our study reveals significant single-mode squeezing in both the driving field and low-order harmonic modes. Additionally, we characterize two-mode squeezing features in the generated states, both between fundamental and harmonic modes, and among the harmonic modes themselves. Using these correlations, we demonstrate the generation of optical Schr\"odinger kitten states through heralding measurements, specifically via photon subtraction in one of the modes influenced by two-mode squeezing.