Photon bunching in high-harmonic emission controlled by quantum light

TL;DR

This paper demonstrates that quantum-optical states can influence high-harmonic emission in semiconductors, revealing photon bunching and suggesting new ways to control and enhance attosecond spectroscopy using quantum correlations.

Contribution

It introduces an experimental method to transduce quantum-optical properties through strong-field nonlinearities in high-harmonic generation, a novel approach in quantum photonics.

Findings

High-harmonic emission exhibits super-Poissonian photon statistics.

Perturbation with a squeezed vacuum induces photon bunching in emitted harmonics.

Quantum states can coherently control high-harmonic generation at short wavelengths.

Abstract

Attosecond spectroscopy comprises several techniques to probe matter through electrons and photons. One frontier of attosecond methods is to reveal complex phenomena arising from quantum-mechanical correlations in the matter system, in the photon fields and among them. Recent theories have laid the groundwork for understanding how quantum-optical properties affect high-field photonics, such as strong-field ionization and acceleration of electrons in quantum-optical fields, and how entanglement between the field modes arises during the interaction. Here we demonstrate a new experimental approach that transduces some properties of a quantum-optical state through a strong-field nonlinearity. We perturb high-harmonic emission from a semiconductor with a bright squeezed vacuum field resulting in the emission of sidebands of the high-harmonics with super-Poissonian statistics, indicating that the emitted photons are bunched. Our results suggest that perturbing strong-field dynamics with quantum-optical states is a viable way to coherently control the generation of these states at short wavelengths, such as extreme ultraviolet or soft X-rays. Quantum correlations will be instrumental to advance attosecond spectroscopy and imaging beyond the classical limits.