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

High-harmonic generation (HHG) has recently emerged as a promising method for generating nonclassical 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 were 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 Schrödinger kitten states through heralding measurements, specifically via photon subtraction in one of the modes influenced by two-mode squeezing. locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon Physics Subject Headings (PhySH)High-order harmonic generationLight-matter interactionQuantum optics