Extreme ultraviolet and X-ray free-electron lasers (FELs) produce short-wavelength pulses with high intensity, ultrashort duration, well-defined polarization and transverse coherence, and have been utilized for many experiments previously possible only at long wavelengths: multiphoton ionization1, pumping an atomic laser2 and four-wave mixing spectroscopy3. However one important optical technique, coherent control, has not yet been demonstrated, because self-amplified spontaneous emission FELs have limited longitudinal coherence4,5,6,7. Single-colour pulses from the FERMI seeded FEL are longitudinally coherent8,9, and two-colour emission is predicted to be coherent. Here, we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and we controlled the asymmetry of the photoelectron angular distribution10,11 by adjusting the phase, with a temporal resolution of 3 as. This opens the door to new short-wavelength coherent control experiments with ultrahigh time resolution and chemical sensitivity.

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We acknowledge the project CENILS (funded by the Central Europe Programme 2007–2013), which provided the wavefront sensor. We acknowledge the support of the Alexander von Humboldt Foundation (Project Tirinto), the Italian Ministry of Research (Project FIRB No. RBID08CRXK and PRIN 2010ERFKXL_006), and funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641789 MEDEA (Molecular Electron Dynamics investigated by IntensE Fields and Attosecond Pulses). K.B., N.D. and J.V. acknowledge support from the US National Science Foundation under grants No. PHY-1430245 and XSEDE-090031. D.I., Y.K. and K.U. are grateful for support from the X-ray Free Electron Laser Priority Strategy Program of MEXT. D.I., K.U. and T.T. are grateful for support from IMRAM, Tohoku University. T.M. and M.M. acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) under grant nos. SFB 925/A1 and A3. A.N.G.G. acknowledges support from the European XFEL. M.N. acknowledges the ERC Starting Research Grant UDYNI, grant agreement no. 307964, EC Seventh Framework Programme.

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  1. Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy

    • K. C. Prince
    • , E. Allaria
    • , C. Callegari
    • , R. Cucini
    • , G. De Ninno
    • , S. Di Mitri
    • , B. Diviacco
    • , E. Ferrari
    • , P. Finetti
    • , D. Gauthier
    • , L. Giannessi
    • , N. Mahne
    • , G. Penco
    • , O. Plekan
    • , L. Raimondi
    • , P. Rebernik
    • , E. Roussel
    • , C. Svetina
    • , M. Trovò
    •  & M. Zangrando
  2. Molecular Model Discovery Laboratory, Department of Chemistry and Biotechnology, Swinburne University of Technology, Melbourne 3122, Australia

    • K. C. Prince
  3. Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, 34149 Basovizza, Italy

    • K. C. Prince
    •  & M. Zangrando
  4. Laboratory of Quantum Optics, University of Nova Gorica, Nova, Gorica 5001, Slovenia

    • G. De Ninno
  5. ENEA C.R. Frascati, 00044 Frascati, Rome, Italy

    • L. Giannessi
  6. University of Trieste, Graduate School of Nanotechnology, 34127 Trieste, Italy

    • C. Svetina
  7. Dipartimento di Fisica, CNR-IFN, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133 Milan, Italy

    • M. Negro
    • , P. Carpeggiani
    • , M. Reduzzi
    •  & G. Sansone
  8. Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia

    • A. N. Grum-Grzhimailo
    • , E. V. Gryzlova
    •  & S. I. Strakhova
  9. Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311, USA

    • K. Bartschat
    • , N. Douguet
    •  & J. Venzke
  10. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan

    • D. Iablonskyi
    • , Y. Kumagai
    • , T. Takanashi
    •  & K. Ueda
  11. Max Planck Institute for Nuclear Physics, Heidelberg 69117, Germany

    • A. Fischer
  12. ISM, Consiglio Nazionale delle Ricerche, 34149 Basovizza, Italy

    • M. Coreno
  13. Physikalisches Institut, Universität Freiburg, 79106 Freiburg, Germany

    • F. Stienkemeier
  14. Institut für Optik und Atomare Physik, TU Berlin, Berlin, Germany

    • Y. Ovcharenko
  15. European XFEL, Albert-Einstein-Ring 19, 22761 Hamburg, Germany

    • T. Mazza
    •  & M. Meyer


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The experiment was conceived by K.C.P., G.S., A.N.G.G. and K.U., and the method of operating FERMI to carry it out was devised by E.A. and L.G. The experiment was prepared and carried out by K.C.P., E.A., C.C., R.C., G.D.N., S.D.M., B.D., E.F., P.F., D.G., L.G., N.M., G.P., O.P., L.R., P.R., E.R., C.S., M.T., M.Z., G.S., P.C., D.I., Y.K., T.T., K.U., A.F., F.S., E.O., T.M., M.N., M.C. and M.M. Theoretical calculations (of machine properties or neon spectra) were performed by E.A., L.G., A.N.G.G., E.V.G., S.I.S., K.B., N.D. and J.V. Detailed data analysis was performed by M.R., P.C. and D.I. The manuscript was drafted by K.C.P. and completed in consultation with all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to K. C. Prince or G. Sansone or K. Ueda.

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