Mid-infrared electric field sampling approaching single-photon sensitivity C. Hofer, D. Gerz, M. Högner, T. P. Butler, C. Gaida, T. Heuermann, M. Gebhardt, N. Karpowicz, J. Limpert, F. Krausz and I. Pupeza EPJ Web Conf., 243 (2020) 16001 Published online: 15 October 2020 DOI: 10.1051/epjconf/202024316001