| Abstract: | High-harmonic generation (HHG) is an extreme nonlinear optical process producing attosecond
light pulses. In this talk, I will present recent works fusing quantum optics and attosecond science
by introducing a quantum description of both driving and emitted fields in HHG. Theoretically, I
will show that the HHG spectrum is sensitive to the quantum state of light: bright squeezed vacuum
extends the HHG cutoff, modifies electron dynamics via an effective photon‑statistics force, and
can imprint squeezing onto high harmonics. Experimentally, I will present the first generation of
XUV attosecond pulses with controllable quantum properties. Driving HHG with a coherent field
perturbed by a variable‑delay squeezed vacuum, we control the quantum state of high harmonics
and reconstruct it using a novel in‑situ quantum state tomography method. This constitutes the first
quantum state reconstruction of attosecond pulses and enables attosecond‑resolved reconstruction
of quantum fluctuations in matter, demonstrated by resolving how quantum light fluctuations
imprint onto tunneling‑barrier fluctuations during HHG |