QUROPE Quantum Information Processing and Communication in Europe

Author(s): Xiaokun Gu, Yujie Wei, Xiaobo Yin, Baowen Li, and Ronggui Yang

The thermal conductivity of 3D samples is usually intensive. However, this holds only when phonon transport is diffusive and the sample is sufficiently large. In this review, a framework is presented that shows how phonon scattering in 2D materials influences thermal transport properties that depend on geometry, substrate and interlayer coupling, and imperfections. These considerations suggest ways of enabling new thermoelectric materials, thermal conductors or insulators, and perhaps even phononic computing devices.

[Rev. Mod. Phys. 90, 041002] Published Tue Nov 13, 2018

Author(s): Edward Witten

The 2016 APS Medal for Excellence in Physics was given to Edward Witten. This contribution was invited in conjunction with this award. These original notes contain concise explanations of some key results in the axiomatic and algebraic approaches to quantum field theory, which are relevant to quantum entanglement. They serve to put the connection between quantum field theory and quantum information theory on a precise and rigorous footing.

[Rev. Mod. Phys. 90, 045003] Published Tue Oct 23, 2018

Author(s): Gianfranco Bertone and Dan Hooper

The standard model of modern cosmology is unthinkable without dark matter, although direct detections are still missing. A broad perspective of how dark matter was postulated and became accepted is presented, from prehistory, over observations of galaxy clusters, galaxy rotation curves, the search for baryonic dark matter, possible alternative explanations via modified gravity, up to the hunt for dark matter particles. The interplay is described between observational discoveries and theoretical arguments which led finally to the adoption of this paradigm.

[Rev. Mod. Phys. 90, 045002] Published Mon Oct 15, 2018

Author(s): F. Sebastian Bergeret, Mikhail Silaev, Pauli Virtanen, and Tero T. Heikkilä

Superconductivity and magnetism both reflect the strong interactions between electrons in a material. When these two effects either compete or collaborate with each other, a variety of new phenomena occur that can be exploited for use in devices. In this Colloquium the authors discuss the experimental and theoretical aspects of how the transport of spin and charge is affected in actual devices through this competition.

[Rev. Mod. Phys. 90, 041001] Published Thu Oct 11, 2018

Author(s): Anna Maciołek and Siegfried Dietrich

Colloidal particles suspended in a solvent experience solvent-mediated interactions due to the adsorption on the colloidal surface. The range of this interaction is set by the bulk correlation length of the solvent, which diverges with universal scaling properties at the critical point of the solvent. The sensitivity of these solvent-mediated interactions, critical Casimir forces, to the thermodynamic state of the solvent presents opportunities to realize the reversible self-assembly of colloids. This review discusses the experimental observations of reversible aggregation and phase transitions due to solvent-mediated interactions, as well as the various theoretical descriptions of this phenomenon.

[Rev. Mod. Phys. 90, 045001] Published Fri Oct 05, 2018

Author(s): Tatsuma Nishioka

In this review the entanglement and Renyi entropies in quantum field theory are described from different points of view, including the perturbative approach and holographic dualities. The applications of these results to constraining renormalization group flows are presented effectively and illustrated with a variety of examples.

[Rev. Mod. Phys. 90, 035007] Published Mon Sep 17, 2018

Author(s): Luca Pezzè, Augusto Smerzi, Markus K. Oberthaler, Roman Schmied, and Philipp Treutlein

Entanglement is the basis of quantum technologies aimed at revolutionizing measurements, computing, and communications. This article reviews methods to improve measurement precision and sensitivity by harnessing entangled states of many atomic probe particles. The achievements of different experimental entanglement schemes are presented with theoretical analyses of their fundamental and practical limits, discussing prospects for applications in clocks, frequency standards, and measurements of forces and fields.

[Rev. Mod. Phys. 90, 035005] Published Wed Sep 05, 2018

Author(s): Daniel Braun, Gerardo Adesso, Fabio Benatti, Roberto Floreanini, Ugo Marzolino, Morgan W. Mitchell, and Stefano Pirandola

Entangled quantum states can enhance measurement precision. But quantum mechanics harbors other possibilities for enhancing precision, including some that have nothing to do with entanglement. This review surveys various strategies with unentangled probes by which measurements have been improved. Among the approaches considered are those that rely on particle statistics and correlations in highly mixed states. Often nonentangled states are more robust, and these approaches are feasible in current experiments: here the current states of research are shown in cold atoms, nonlinear optics, and nanomechanical oscillators.

[Rev. Mod. Phys. 90, 035006] Published Wed Sep 05, 2018

Author(s): Martin Freer, Hisashi Horiuchi, Yoshiko Kanada-En’yo, Dean Lee, and Ulf-G. Meißner

In most nuclei, protons and neutrons are smoothly distributed throughout the nuclear volume. Exceptions to this rule are molecularlike states, especially in light nuclei, where light nuclear clusters such as alpha particles are present. The most prominent example is the 7.65 MeV Hoyle state in carbon-12 that plays an essential role in the production of carbon in stars in the triple-alpha process. This work reviews progress and prospects in the studies of nuclear clustering, including molecular states in alpha-conjugate and neutron-rich systems.

[Rev. Mod. Phys. 90, 035004] Published Tue Aug 28, 2018

Author(s): Seogjoo J. Jang and Benedetta Mennucci

Photosynthetic bacteria, algae, and plants convert solar energy into biochemical fuel via light-harvesting complexes comprised of proteins and pigments. Pigments absorb photons by exciting electron-hole pairs that move readily to other pigments. How biology utilizes such quantum processes at room temperature to achieve efficiency of energy transfer is of interest to physicists. This article reviews computational and spectroscopic advances in understanding the energy conversion and energy transport of such a magnificent nanorectenna.

[Rev. Mod. Phys. 90, 035003] Published Tue Aug 21, 2018

Author(s): Evelyn Tang and Danielle S. Bassett

Biological networks are notoriously complex to understand and hence challenging to control. The brain is possibly the most sophisticated network in nature and only recently have we started to comprehend the mechanics of its operation and control. This Colloquium reviews the latest theoretical and technological developments in this emergent and exciting area of research.

[Rev. Mod. Phys. 90, 031003] Published Tue Aug 14, 2018

Author(s): M. C. Downer, R. Zgadzaj, A. Debus, U. Schramm, and M. C. Kaluza

Plasma-based electron accelerators rely on excitation of light-speed plasma density waves and associated ultrahigh electric fields to accelerate electrons to ultrarelativistic energy. Intrinsic time and length scales of these plasma waves are typically a few tens of femtoseconds and micrometers and result in ultrashort electron bunches with often even smaller temporal and spatial dimensions. In this article the progress and challenges of diagnosing the plasma waves, the excited fields, and ensuing particle bunches are reviewed.

[Rev. Mod. Phys. 90, 035002] Published Wed Aug 08, 2018

Author(s): D. E. Chang, J. S. Douglas, A. González-Tudela, C.-L. Hung, and H. J. Kimble

Quantum optics has advanced tremendously over the past two decades by combining ultracold atoms with diverse optical systems. However, fundamental and technical issues place constraints that limit further advances. This Colloquium examines new paradigms for strong quantum interactions of matter and light by way of atoms and photons in nanoscopic dielectric lattices, including novel quantum phases of atoms, photons, and phonons.

[Rev. Mod. Phys. 90, 031002] Published Wed Aug 01, 2018