title: Direct observation of ultrafast many-body electron dynamics in an ultracold Rydberg gas.
abstract: Many-body correlations govern a variety of important quantum phenomena such as the emergence of superconductivity and magnetism. Understanding quantum many-body systems is thus one of the central goals of modern sciences. Here we demonstrate an experimental approach towards this goal by utilizing an ultracold Rydberg gas generated with a broadband picosecond laser pulse. We follow the ultrafast evolution of its electronic coherence by time-domain Ramsey interferometry with attosecond precision. The observed electronic coherence shows an ultrafast oscillation with a period of 1 femtosecond, whose phase shift on the attosecond timescale is consistent with many-body correlations among Rydberg atoms beyond mean-field approximations. This coherent and ultrafast many-body dynamics is actively controlled by tuning the orbital size and population of the Rydberg state, as well as the mean atomic distance. Our approach will offer a versatile platform to observe and manipulate non-equilibrium dynamics of quantum many-body systems on the ultrafast timescale.
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.|SOKENDAI (The Graduate University for Advanced Studies), Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takei
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.|SOKENDAI (The Graduate University for Advanced Studies), Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Christian
authors.initials: C
authors.lastname: Sommer
authors.affiliation: Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: Claudiu
authors.initials: C
authors.lastname: Genes
authors.affiliation: IPCMS (UMR 7504) and ISIS (UMR 7006), University of Strasbourg and CNRS, 67000 Strasbourg, France.
authors.forename: Guido
authors.initials: G
authors.lastname: Pupillo
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Goto
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.|SOKENDAI (The Graduate University for Advanced Studies), Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Koyasu
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.|Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Chiba
authors.affiliation: Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany.|Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Matthias
authors.initials: M
authors.lastname: Weidemüller
authors.affiliation: Department of Photo-Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan.|SOKENDAI (The Graduate University for Advanced Studies), Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ohmori