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arXiv · 2603.01315

Intermodal entanglement in a quantum optical model of HHG due to the back-action on the driving field

Ákos Gombkötő·Péter Ádám·David Theidel·Tamás Kiss
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Abstract

Preparation of nonclassical light with special quantum properties is essential for quantum technologies. High-harmonic generation (HHG) is a process which not only enables the creation of attosecond pulses but also has the potential to generate light with intricate quantum properties. In a recent experiment [PRX Quantum 5. 040319], nonclassical inter-harmonic correlations have been measured from a HHG source between low-order harmonics. In this work, we theoretically investigate entanglement between different harmonics within an effective, phenomenological quantum optical model. This model implements a significant degree of simplification regarding the processes within the target material, treating the material through susceptibilities, as it is usual in quantum optics. Such an approach yields a general description of HHG in the few-harmonic generation regime, permitting the implications that can be derived within it to hold broadly within the domain of validity. We find that entanglement is produced as a result of the often neglected back-action. We can qualitatively reproduce experimentally measured nonclassicalities, which suggests that intermodal entanglement can, to an extent, be considered a universal phenomenon associated with HHG, rather than a result of using specific material targets.

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Ákos Gombkötő, Péter Ádám, David Theidel, Tamás Kiss. 2026-03-01. Intermodal entanglement in a quantum optical model of HHG due to the back-action on the driving field. https://doi.org/10.1103/wf93-dyn6

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