QUROPE Quantum Information Processing and Communication in Europe

Author(s): C. Reichhardt, C. J. O. Reichhardt, and M. V. Milošević

The study of skyrmions has grown as they have been realized in topologically stable spin-textured magnetic excitations. This overview treats magnetic skyrmions and skyrmion assemblies using a particle-based approach to describe a system in which the energy scales of the skyrmion-skyrmion interactions, sample disorder, temperature, and drive magnitude compete. Pinning and dynamic effects of skyrmions interacting with disordered or ordered substrates are of technological importance for skyrmion applications. Analogs to vortices in type-II superconductors, charge density waves, and colloidal particles are presented.

[Rev. Mod. Phys. 94, 035005] Published Tue Sep 20, 2022

Author(s): Debanjan Chowdhury, Antoine Georges, Olivier Parcollet, and Subir Sachdev

The Sachdev-Ye-Kitaev (SYK) model is a solvable model of a many-body quantum system that has stimulated interest in both condensed matter physics and quantum gravity. This review focuses on the insights provided by the SYK model, which has no quasiparticle excitations, into the physics of Planckian non-Fermi-liquid metals. This is discussed for a range of strongly correlated models and in relation to experiments on strongly correlated materials. Also included is a discussion of recent developments regarding the connections between the SYK model and the quantum theory of black holes.

[Rev. Mod. Phys. 94, 035004] Published Wed Sep 14, 2022

Author(s): Amber Boehnlein, Markus Diefenthaler, Nobuo Sato, Malachi Schram, Veronique Ziegler, Cristiano Fanelli, Morten Hjorth-Jensen, Tanja Horn, Michelle P. Kuchera, Dean Lee, Witold Nazarewicz, Peter Ostroumov, Kostas Orginos, Alan Poon, Xin-Nian Wang, Alexander Scheinker, Michael S. Smith, and Long-Gang Pang

Nuclear physics deals with complex systems, large datasets, and complicated correlations between parameters, which makes the field suitable for the application of machine learning techniques. Machine learning can help classify and analyze data, find hidden correlations, and assist in the design of new experiments and detectors. This Colloquium explains how this will lead to advances in nuclear theory, experimental methods and data acquisition, and accelerator technology.

[Rev. Mod. Phys. 94, 031003] Published Thu Sep 08, 2022

Author(s): Guillermo F. Quinteiro Rosen, Pablo I. Tamborenea, and Tilmann Kuhn

The interaction between light and matter is a subject of ongoing fundamental interest at the intersection of optics and condensed-matter physics. This review discusses how the structuring of light into optical vortices leads to distinctive optical selection rules and coupling to sample geometry, requiring reformulation of the standard theory for interaction of plane-wave light with matter. The interactions of optical vortices with semiconductor nanostructures, quantum rings, and 2D materials are presented. The results suggest further avenues for fundamental investigation as well as current and prospective applications in quantum control, communications, and sensing.

[Rev. Mod. Phys. 94, 035003] Published Thu Aug 25, 2022

Author(s): S. S. Harilal, M. C. Phillips, D. H. Froula, K. K. Anoop, R. C. Issac, and F. N. Beg

Laser-produced plasmas (LPP) are important for fundamental research, industrial, and medical applications. Typical laser intensities used for producing these plasmas are low to moderate, and the plasma conditions change with both space and time, can be spatially inhomogeneous, and have various degrees of ionization states for the ionized material. Measuring these properties is key for understanding, tailoring, and optimizing the plasma conditions. This review provides an overview of optical diagnostic tools employed for the characterization of the LPPs and emphasizes techniques, associated assumptions, and challenges.

[Rev. Mod. Phys. 94, 035002] Published Mon Aug 15, 2022

Author(s): Charley Presigny and Fabrizio De Vico Fallani

The brain is a formidably complex system made of neurons and neuronal ensembles that segregate and integrate information across organized layers at multiple spatial and temporal scales. A physicist’s perspective is provided on modeling the brain as interconnected and multilayered networks that grow into complex organizations for processing information dynamically. The analytical tools for multilayer networks root deeply in statistical physics that render interpretable features connecting network patterns as biomarkers to a mental state or brain diseases.

[Rev. Mod. Phys. 94, 031002] Published Tue Aug 02, 2022

Author(s): Peter Talkner and Peter Hänggi

[Rev. Mod. Phys. 94, 039901] Published Fri Jul 29, 2022

Author(s): C. Cisowski, J. B. Götte, and S. Franke-Arnold

This Colloquium reviews the role of geometric phases in optics from the perspective of fiber bundle theory. The transformation of the polarization of light by discrete optical components illustrates many elements of the theoretical formalism, and an outlook is presented for the study and application of geometric phases in higher dimensions through analyses of higher order Gaussian modes and general vectorial fields.

[Rev. Mod. Phys. 94, 031001] Published Mon Jul 18, 2022

Author(s): Chao-Yang Lu, Yuan Cao, Cheng-Zhi Peng, and Jian-Wei Pan

The Micius satellite, launched from China in August 2016, is the first and only satellite dedicated entirely to quantum experiments. The ultralow loss transmission of photons on most of the path between ground and space enables quantum communication capabilities that are still far from being realized. This review details the commissioning of Micius as a full quantum communications system, and describes the achievement of global-scale quantum key distribution, entanglement distribution, and other fundamental studies, with this unique space-based system.

[Rev. Mod. Phys. 94, 035001] Published Wed Jul 06, 2022

Author(s): Christopher Portmann and Renato Renner

Secure communications is a vital need of the world, and the basic features of quantum mechanics seemingly offer fundamental new tools for achieving this security. But do these tools really work? This review gives due attention to the real-world problems with experimental quantum cryptography, but the heart of the review is an in-depth survey of the analyses developed to prove the security of the basic quantum techniques introduced by Wiesner, Ekert, Bennett, and Brassard. A broader set of cryptographic tasks have quantum aspects which are also discussed here.

[Rev. Mod. Phys. 94, 025008] Published Wed Jun 29, 2022

Author(s): Armin Hochrainer, Mayukh Lahiri, Manuel Erhard, Mario Krenn, and Anton Zeilinger

The double-slit experiment manifests the duality between wave interference and the distinguishability of paths taken by a particle though an apparatus. This article reviews advanced developments of these concepts with pairs of particles, starting with experiments on quantum foundations with photon pairs in the 1990s. These experiments now form the basis for applications in quantum information as well as for spatial imaging and spectroscopy that is performed without ever detecting the photons that interacted with the object.

[Rev. Mod. Phys. 94, 025007] Published Tue Jun 21, 2022

Author(s): Reinhard Genzel

The 2020 Nobel Prize for Physics was shared by Roger Penrose, Andrea Ghez, and Reinhard Genzel. This paper is the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 94, 020501] Published Fri Jun 17, 2022

Author(s): Feng-Kun Guo, Christoph Hanhart, Ulf-G. Meißner, Qian Wang, Qiang Zhao, and Bing-Song Zou

[Rev. Mod. Phys. 94, 029901] Published Mon Jun 13, 2022