Subcycle tomography of quantum light
Phys. Rev. A 113, 043703 – Published 1 April, 2026
DOI: https://doi.org/10.1103/m5ln-m31l
Abstract
A concept for the analysis of quantum light at its most fundamental timescale is provided, namely, at the oscillation cycle of a mode or the inverse frequency of an involved photon. We demonstrate theoretically how local quantum measurements allow one to reconstruct and visualize a quantum field under study at subcycle scales, even when its temporal-mode structure is a priori unknown. Generalized subcycle-resolved field quadratures for each value of the time delay with respect to a sampling pulse and for each value of the carrier-envelope phase of the sampled field are introduced. Generation and tomography of ultrabroadband squeezed states as well as photon-subtracted states derived from them are described, incorporating also single-photon states. We decompose the fields into separable modes that are localized in time and illustrate the dynamics of their contributions in the detection process. Since the temporal sampling requires millions of repetitions for each time delay, an efficient reconstruction scheme is developed based on the Gram-Charlier expansion, allowing us to minimize the amount of different phase values required for a desired precision. Our results represent a cornerstone in the emerging chapter of quantum physics termed time-domain quantum optics.
