Emergence of Nonclassical Light in Laser-Driven Quantum Systems

This paper introduces a fully quantum, analytically tractable theory to explain the emergence of nonclassical light in high-order harmonic generation (HHG). It addresses a gap in understanding the quantum optical character of HHG, which is a widely tunable and bright source of coherent radiation. The theory allows for the predictive design of bright, high-photon-number quantum states at tunable frequencies, opening new avenues for tabletop quantum light sources.