The Quantum Polariton Hamiltonian that Reproduces the Same High-Harmonic Generation Spectra as the Classical Hamiltonian in Strong Laser Fields

This manuscript investigates the possibility of defining a quantum Hamiltonian that leads to the same high-harmonic generation (HHG) spectra as those predicted by Floquet theory in the regime where the number of infrared (IR) pump photons is much larger than the number of emitted UV photons. The key assumption underlying our derivation is that the intensity of the emitted high harmonics is many orders of magnitude smaller than that of the IR laser, and that the emission of the Nnt harmonic results from the absorption of N IR photons.