Volume 12 Issue 11, November 2016

Volume 12 Issue 11

The realization of a quantum kicked top provides evidence for ergodic dynamics and thermalization in a small quantum system consisting of three superconducting qubits.Letter p1037 IMAGE: ROUSHAN, GOOGLE QUANTUM HARDWARE LAB COVER DESIGN: ALLEN BEATTIE

Editorial

Thesis

Books and Arts

Research Highlights

News and Views

  • News & Views |

    A wire moving at constant speed through superfluid helium can considerably exceed the Landau critical velocity.

    • William P. Halperin
  • News & Views |

    Although Dirac fermions in graphene can tunnel through potential barriers without reflection, two experiments show how they can temporarily be trapped inside nanoscale graphene quantum dots.

    • Heejun Yang
  • News & Views |

    Intuition informs a widespread policy of epidemic response, replacing infected workers in classrooms or hospitals with healthy substitutes. But modelling now suggests that this mechanism may be a key factor in the accelerated spread of an epidemic.

    • Thilo Gross
  • News & Views |

    The physical properties of ice are governed by its tetrahedral network of hydrogen bonds and the ice rules that determine the distribution of the protons. Deviations from the tetrahedral structure and violations of these rules can lead to surprising phenomena, such as the ferroelectric state now reported for thin films of epitaxial ice.

    • Ivan A. Ryzhkin
  • News & Views |

    Solar eruptions are triggered by magnetic stress building up in the corona due to the motion of the Sun's dense surface. New observations reveal that these eruptions can, in turn, induce the rotational motion of sunspots.

    • Guillaume Aulanier

Letters

  • Letter |

    Using a technique inspired by Ramsey spectroscopy it is now possible to coherently control free electrons in an electron microscope.

    • Katharina E. Echternkamp
    • , Armin Feist
    • , Sascha Schäfer
    •  & Claus Ropers
  • Letter |

    Josephson plasma waves — electromagnetic waves propagating between layered superconductors — lie at the basis of a broad variety of phenomena. Now, parametric amplification of such waves has been shown by tuning the phase between pump and seed waves.

    • S. Rajasekaran
    • , E. Casandruc
    • , Y. Laplace
    • , D. Nicoletti
    • , G. D. Gu
    • , S. R. Clark
    • , D. Jaksch
    •  & A. Cavalleri
  • Letter |

    An experiment reports the unexpected behaviour of an object in uniform motion in superfluid helium-3 above the Landau critical velocity — the limit above which it can generate excitations at no energy cost.

    • D. I. Bradley
    • , S. N. Fisher
    • , A. M. Guénault
    • , R. P. Haley
    • , C. R. Lawson
    • , G. R. Pickett
    • , R. Schanen
    • , M. Skyba
    • , V. Tsepelin
    •  & D. E. Zmeev
  • Letter |

    Two distinct valleys in the electronic band structure of graphene provide an additional degree of freedom that could be exploited for devices. Conservation of this valley symmetry can now be seen in the quantized conductance of graphene nanoribbons.

    • Minsoo Kim
    • , Ji-Hae Choi
    • , Sang-Hoon Lee
    • , Kenji Watanabe
    • , Takashi Taniguchi
    • , Seung-Hoon Jhi
    •  & Hu-Jong Lee
  • Letter |

    Relativistic Dirac fermions can be locally confirmed in nanoscale graphene quantum dots using electrostatic gating, and directly imaged using scanning tunnelling microscopy before escaping via Klein tunnelling.

    • Juwon Lee
    • , Dillon Wong
    • , Jairo Velasco Jr
    • , Joaquin F. Rodriguez-Nieva
    • , Salman Kahn
    • , Hsin-Zon Tsai
    • , Takashi Taniguchi
    • , Kenji Watanabe
    • , Alex Zettl
    • , Feng Wang
    • , Leonid S. Levitov
    •  & Michael F. Crommie
  • Letter |

    The realization of a quantum kicked top provides evidence for ergodic dynamics and thermalization in a small quantum system consisting of three superconducting qubits.

    • C. Neill
    • , P. Roushan
    • , M. Fang
    • , Y. Chen
    • , M. Kolodrubetz
    • , Z. Chen
    • , A. Megrant
    • , R. Barends
    • , B. Campbell
    • , B. Chiaro
    • , A. Dunsworth
    • , E. Jeffrey
    • , J. Kelly
    • , J. Mutus
    • , P. J. J. O’Malley
    • , C. Quintana
    • , D. Sank
    • , A. Vainsencher
    • , J. Wenner
    • , T. C. White
    • , A. Polkovnikov
    •  & J. M. Martinis
  • Letter |

    The common policy of replacing infected individuals with healthy substitutes can have the effect of accelerating disease transmission. A dynamic network model suggests that standard modelling approaches underplay the effect of network structure.

    • Samuel V. Scarpino
    • , Antoine Allard
    •  & Laurent Hébert-Dufresne

Articles

  • Article |

    A method for analysing STM data enables the recovery of information about quasiparticle scattering in the form of holographic maps. The approach is verified for superconducting cuprates, but may find applications in heavy-fermion materials research.

    • Emanuele G. Dalla Torre
    • , Yang He
    •  & Eugene Demler
  • Article |

    Studies of supercurrent phenomena, such as superconductivity and superfluidity, are usually restricted to cryogenic temperatures, but evidence suggests that a magnon supercurrent can be excited in a Bose–Einstein magnon condensate at room temperature.

    • Dmytro A. Bozhko
    • , Alexander A. Serga
    • , Peter Clausen
    • , Vitaliy I. Vasyuchka
    • , Frank Heussner
    • , Gennadii A. Melkov
    • , Anna Pomyalov
    • , Victor S. L’vov
    •  & Burkard Hillebrands
  • Article |

    Relativistic Dirac fermions can be locally confirmed in nanoscale graphene quantum dots using electrostatic gating, and directly imaged using scanning tunnelling microscopy before escaping via Klein tunnelling.

    • Christopher Gutiérrez
    • , Lola Brown
    • , Cheol-Joo Kim
    • , Jiwoong Park
    •  & Abhay N. Pasupathy
  • Article |

    Multiplex networks are shown to harbour significant correlations between layers. A framework describing the correlations enables multilayer community and link detection, and reveals that they improve navigation — but only when they’re strong.

    • Kaj-Kolja Kleineberg
    • , Marián Boguñá
    • , M. Ángeles Serrano
    •  & Fragkiskos Papadopoulos

Measure for Measure

  • Measure for Measure |

    Nick van Remortel demystifies natural unit systems — and advises what to do when you see a mass expressed in GeV.

    • Nick van Remortel

Correction