title: Interferometric phase detection at x-ray energies via Fano resonance control.
abstract: Modern x-ray light sources promise access to structure and dynamics of matter in largely unexplored spectral regions. However, the desired information is encoded in the light intensity and phase, whereas detectors register only the intensity. This phase problem is ubiquitous in crystallography and imaging and impedes the exploration of quantum effects at x-ray energies. Here, we demonstrate phase-sensitive measurements characterizing the quantum state of a nuclear two-level system at hard x-ray energies. The nuclei are initially prepared in a superposition state. Subsequently, the relative phase of this superposition is interferometrically reconstructed from the emitted x rays. Our results form a first step towards x-ray quantum state tomography and provide new avenues for structure determination and precision metrology via x-ray Fano interference.
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany.
authors.forename: K P
authors.initials: KP
authors.lastname: Heeg
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ott
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Schumacher
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: H-C
authors.initials: HC
authors.lastname: Wille
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Röhlsberger
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Pfeifer
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Evers