Photon-statistics force in ultrafast electron dynamics

In strong-field physics and attosecond science, intense light induces ultrafast electron dynamics. Such ultrafast dynamics of electrons in matter is at the core of phenomena such as high-harmonic generation, where these dynamics lead to the emission of extreme-ultraviolet bursts with attosecond duration. So far, all ultrafast dynamics of matter were understood to purely originate from the classical vector potential of the driving light, disregarding the influence of the quantum nature of light. Here we show theoretically that the dynamics of matter driven by bright (intense) light significantly depend on the quantum state of the driving light through its quantum noise, which induces an effective photon-statistics force. To provide a unified framework for the analysis and control over such a force, we extend the strong-field approximation theory to account for non-classical driving light. Our quantum strong-field approximation theory shows that in high-harmonic generation, experimentally feasible squeezing of the driving light can shift and shape electronic trajectories and attosecond pulses at the scale of hundreds of attoseconds. Our work presents a new degree of freedom for attosecond spectroscopy, by relying on non-classical electromagnetic fields, and more generally, introduces a direct connection between attosecond science and quantum optics. Strong-field approximation theory is extended to account for non-classical driving light. This extended theory predicts that ultrafast dynamics of strongly light-driven matter significantly depends on the quantum state of the driving light, particularly on its photon statistics.