Theoretical physics articles within Nature Communications

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  • Article |

    Topological phases are unusual states of matter whose properties are robust against small perturbations. Using a photonic quantum walk system, Kitagawaet al. simulate one-dimensional topological phases and reveal novel topological phenomena far from the static or adiabatic regimes.

    • Takuya Kitagawa
    • , Matthew A. Broome
    •  & Andrew G. White

  • Article |

    The electromotive force is a well established phenomenon that is induced by a varying magnetic field. Here, Tanabeet al. report a compelling experimental confirmation of its spin-induced analogue, the spinmotive force.

    • K. Tanabe
    • , D. Chiba
    •  & T. Ono

  • Article |

    Quantum phase transitions are generally associated with many-body quantum systems undergoing changes between different phases. This study examines the connection between such phase transitions and quantum information processing, and finds that different quantum phases can have different computational power.

    • Jian Cui
    • , Mile Gu
    •  & Vlatko Vedral

  • Article |

    Percolation transitions indicate the threshold above which a network can operate. This work examines a general class of models known as hierarchical networks, and shows they can be made to percolate explosively, if they share features of so-called 'small-world' networks.

    • Stefan Boettcher
    • , Vijay Singh
    •  & Robert M. Ziff

  • Article |

    Stochastic processes play an important role in a broad range of scientific problems. This study demonstrates that a large class of such processes are most efficiently simulated by quantum mechanical models, thus reducing the complexity required to simulate them using classical models.

    • Mile Gu
    • , Karoline Wiesner
    •  & Vlatko Vedral

  • Article |

    The spin–orbit interaction affects the electronic structure of many solids to give rise to a host of unusual phenomena. Bahramyet al.theoretically examine its role in the non-centrosymmetric compound BiTeI, and find that under the application of pressure, it leads to topologically insulating behaviour.

    • M.S. Bahramy
    • , B.-J. Yang
    •  & N. Nagaosa

  • Article |

    The dynamics of isolated quantum systems can either be strongly correlated with their initial state, or chaotic, as they relax into thermal equilibrium. Olshaniiet al. present a simple, exactly solvable model that captures the transition between these two limiting cases, and suggests it may have some universal features.

    • Maxim Olshanii
    • , Kurt Jacobs
    •  & Vladimir A. Yurovsky

  • Article
    | Open Access

    Although they offer significant promise, practical implementations of quantum key distribution are often not as rigorous as theory predicts. This study demonstrates how two instances of such discrepancies can be resolved by taking advantage of an enotropic formulation of the uncertainty principle.

    • Marco Tomamichel
    • , Charles Ci Wen Lim
    •  & Renato Renner

  • Article
    | Open Access

    Quantum mechanics predicts that objects can simultaneously exist in a superposition of two states. Kneeet al.propose and demonstrate experimentally a protocol which fully confirms this prediction, by testing the so-called Leggett–Garg inequality in a non-invasive manner.

    • George C. Knee
    • , Stephanie Simmons
    •  & Simon C. Benjamin

  • Article
    | Open Access

    In the theory of general relativity time flows at different rates depending on the space–time geometry. Here, a drop in the visibility of a quantum 'clock' interference in a gravitational potential is predicted, which cannot be explained without the general relativistic notion of time.

    • Magdalena Zych
    • , Fabio Costa
    •  & Časlav Brukner

  • Article
    | Open Access

    Quantum-mechanical predictions are generally probabilistic. Here, assuming freely chosen measurements, it is shown that enhanced predictions are not possible and, thus, randomness is inherent in quantum theory: a result that has applications in fields such as quantum cryptography.

    • Roger Colbeck
    •  & Renato Renner

  • Article |

    Pagerank is widely used to rank web content; however, it is unknown how network topology affects its performance. The authors demonstrate that, in random networks, pagerank is sensitive to perturbations in topology, whereas scale-free networks contain a few super-stable nodes whose ranking is exceptionally stable.

    • Gourab Ghoshal
    •  & Albert-László Barabási

  • Article
    | Open Access

    In some iron-based materials, unconventional superconductivity can emerge near a quantum phase transition where long-range magnetic order vanishes. Giovannettiet al.show that the magnetic quantum phase transition in an iron pnictide superconductor is very close to the quantum tricritical point.

    • Gianluca Giovannetti
    • , Carmine Ortix
    •  & José Lorenzana

  • Article |

    Anyons are particles with fractional statistics that interpolate between bosons and fermions, and are thought to exist in low-dimensional systems. Keilmannet al. propose an experimental system to create anyons in one-dimensional optical lattices using assisted Raman tunnelling.

    • Tassilo Keilmann
    • , Simon Lanzmich
    •  & Marco Roncaglia

  • Article |

    Quantum-enhanced measurements use quantum mechanical effects to enhance measurement sensitivity of classical quantities; but the required quantum states are generally highly entangled and difficult to produce. In this study, the use of entangled states is avoided allowing Heisenberg-limited measurements.

    • Daniel Braun
    •  & John Martin

  • Article |

    The nonlocality of a quantum state is often difficult to predict. Here, Cavalcanti and colleagues devise a method based on networks that makes this characterization much easier, revealing that the nonlocality of a quantum state depends on the context of the measurement.

    • Daniel Cavalcanti
    • , Mafalda L. Almeida
    •  & Antonio Acín

  • Article |

    Error correction in quantum computing can be implemented using transversal gates, which in turn rely on the availability of so-called magic states. The authors experimentally show that it is possible to improve the fidelity of these states by distilling five of them into one.

    • Alexandre M. Souza
    • , Jingfu Zhang
    •  & Raymond Laflamme

  • Article |

    Direct quantum state tomography—deducing the state of a system from measurements—is mostly unfeasible due to the exponential scaling of measurement number with system size. The authors present two new schemes, which scale linearly in this respect, and can be applied to a wide range of quantum states.

    • Marcus Cramer
    • , Martin B. Plenio
    •  & Yi-Kai Liu

  • Article |

    Two principles have recently been proposed as attempts to provide physical axioms for quantum mechanics: causality and macroscopic locality. Cavalcanti and colleagues show here that the two are not equivalent, giving confidence in information causality as a constraint for correlations obtained in experiments.

    • Daniel Cavalcanti
    • , Alejo Salles
    •  & Valerio Scarani

  • Article |

    Routing packets on the growing and changing underlying structure of the Internet is challenging and currently based only on local connectivity. Here, a global Internet map is devised: with a greedy forwarding algorithm, it is robust with respect to network growth, and allows speeds close to the theoretical best.

    • Marián Boguñá
    • , Fragkiskos Papadopoulos
    •  & Dmitri Krioukov

  • Article |

    Electrons in metals at extremely high magnetic fields show interesting quantum structures. The authors measure the angle-dependent Nernst effect with high precision and show that, for bismuth, Coulomb interactions between the electrons become important in this ultraquantum regime.

    • Huan Yang
    • , Benoît Fauqué
    •  & Kamran Behnia

  • Article |

    The magnetic flux lines in a superconductor present intricate patterns, whose origins are seldom understood. Here the authors link them to geometrical effects by means of the 'hairy ball' theorem, which states that for a vector field on a sphere there will always be at least one singularity.

    • Mark Laver
    •  & Edward. M. Forgan

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