title: Measurement of a vacuum-induced geometric phase.
abstract: Berry's geometric phase naturally appears when a quantum system is driven by an external field whose parameters are slowly and cyclically changed. A variation in the coupling between the system and the external field can also give rise to a geometric phase, even when the field is in the vacuum state or any other Fock state. We demonstrate the appearance of a vacuum-induced Berry phase in an artificial atom, a superconducting transmon, interacting with a single mode of a microwave cavity. As we vary the phase of the interaction, the artificial atom acquires a geometric phase determined by the path traced out in the combined Hilbert space of the atom and the quantum field. Our ability to control this phase opens new possibilities for the geometric manipulation of atom-cavity systems also in the context of quantum information processing.
authors.affiliation: Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Simone
authors.initials: S
authors.lastname: Gasparinetti
authors.affiliation: Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Berger
authors.affiliation: Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Abdufarrukh A
authors.initials: AA
authors.lastname: Abdumalikov
authors.affiliation: Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Marek
authors.initials: M
authors.lastname: Pechal
authors.affiliation: IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Filipp
authors.affiliation: Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Wallraff
mesh_terms: D000465:Algorithms; D008962:Models, Theoretical; D011789:Quantum Theory; D014618:Vacuum
keywords: Berry phase; circuit-QED; transmon; vacuum fluctuations