Noisy intermediate-scale quantum algorithms Kishor Bharti, Alba Cervera-Lierta, Thi Ha Kyaw, Tobias Haug, Sumner Alperin-Lea, Abhinav Anand, Matthias Degroote, Hermanni Heimonen, Jakob S. Kottmann, Tim Menke, Wai-Keong Mok, Sukin Sim, Leong-Chuan Kwek, and Alán Aspuru-Guzik Rev. Mod. Phys. 94, 015004 (2022) – Published 15 February 2022 Noisy quantum computers can in principle perform reliable quantum computations, but truly scalable systems require noise levels lower than are presently achieved. Still, moderate-complexity computations can be performed. This review discusses what is possible in this “noisy intermediate scale” quantum (NISQ) era. Topic areas include the simulation of many-body physics and chemistry, combinatorial optimization, and machine learning. It is evident that the NISQ era has produced new paradigms for programming that will be built upon as quantum computers are further perfected. Show Abstract PDFHTML Semitauonic b -hadron decays: A lepton flavor universality laboratory Florian U. Bernlochner, Manuel Franco Sevilla, Dean J. Robinson, and Guy Wormser Rev. Mod. Phys. 94, 015003 (2022) – Published 4 February 2022 While searches for interactions at high-energy experiments have yielded more stringent bounds on new physics, the discovery potential of indirect searches has drawn renewed attention. The standard model predicts that physical processes involving charged leptons should feature lepton flavor universality relations among physical observables. Observation of lepton flavor universality violation would thus establish the presence of new physics beyond the standard model. This article provides a review of lepton flavor universality violation in semileptonic b -hadron decays. It investigates the current measurements and their world averages, and examines the future, outlining the expected evolution of the experimental uncertainties and the prospects for future discoveries. Show Abstract PDFHTML The proton charge radius H. Gao and M. Vanderhaeghen Rev. Mod. Phys. 94, 015002 (2022) – Published 21 January 2022 The proton is responsible for about half the mass in our personal lives. So it is perhaps surprising that little is known about how it got here or how it is bound from its fundamental quark and gluon constituents. This uncertainty is the largest source of error to extracting some fundamental constants of nature. One observable that probes the internal structure of the proton and tests our theoretical description of it is the proton charge radius. The radius is sensitive to quantum electrodynamics and quantum chromodynamics and helps to constrain new physics. This review presents the current status among the four types of experiments to measure the radius: electron scattering, muon scattering, electronic hydrogen spectroscopy, and muonic hydrogen spectroscopy. Show Abstract PDFHTML The climate system and the second law of thermodynamics Martin S. Singh and Morgan E O’Neill Rev. Mod. Phys. 94, 015001 (2022) – Published 6 January 2022 While the first law of thermodynamics is a well-established principle underlying all models of Earth’s climate system, applications of the second law in climate science are active areas of research. This review summarizes how the relationships between Earth’s entropy export and internal entropy production provide insights into Earth’s climate. These applications include heat-engine analogs for atmospheric convection, tropical cyclones, and large-scale atmospheric heat transport. Open issues addressed include the ongoing debate on whether the climate system maximizes entropy production. Show Abstract PDFHTML Matrix product states and projected entangled pair states: Concepts, symmetries, theorems J. Ignacio Cirac, David Pérez-García, Norbert Schuch, and Frank Verstraete Rev. Mod. Phys. 93, 045003 (2021) – Published 17 December 2021 Many-body wave functions can be described effectively by local tensors in matrix product states and projected entangled pair states. This article reviews how these theories provide not only numerical methods but also insights of a more fundamental nature into the structures of states with global entanglement patterns and topological quantum order. Show Abstract PDFHTML Water vapor and lapse rate feedbacks in the climate system Robert Colman and Brian J. Soden Rev. Mod. Phys. 93, 045002 (2021) – Published 30 November 2021 Water vapor is the most important greenhouse gas in Earth’s atmosphere, absorbing more solar terrestrial radiation than any other atmospheric constituent. Because vapor concentrations increase exponentially with temperature, the interaction of water vapor with the vertical thermal structure of the atmosphere introduces a critical positive climate feedback to planetary warming induced by anthropogenic greenhouse gases. This article describes the relevant physical processes, empirical evidence for the feedbacks, representation of these processes in global models of the Earth system, and gaps requiring further research. Show Abstract PDFHTML 1 citation The Fibonacci quasicrystal: Case study of hidden dimensions and multifractality Anuradha Jagannathan Rev. Mod. Phys. 93, 045001 (2021) – Published 9 November 2021 The one-dimensional Fibonacci chain is a toy model central to theoretical studies of the physics of electronic states in quasiperiodic structures. This review surveys the state of the art of methods to study the energy spectra and states of Fibonacci chain models, including exact solutions, renormalization group, perturbation theory, and numerical analysis. Results highlight distinctive properties of Fibonacci chain systems, including projection from higher dimensions, nontrivial topological properties, multifractal states, and hyperuniformity. Questions of current interest include the effects of disorder and interactions and experimental realizations in electronic, cold atom, phononic, and photonic systems. Show Abstract PDFHTML 3 citations Colloquium: Nonthermal pathways to ultrafast control in quantum materials Alberto de la Torre, Dante M. Kennes, Martin Claassen, Simon Gerber, James W. McIver, and Michael A. Sentef Rev. Mod. Phys. 93, 041002 (2021) – Published 14 October 2021 Ultrafast laser pulses can be used to drive materials into nonequilibrium states that have unusual properties and are promising for technological applications. Different classes of phenomena are observed during and after the optical illumination. This Colloquium discusses the recent developments in this field, and the prospects for using these techniques to create materials with novel functionalities in a controlled way. Show Abstract PDFHTML 1 citation Colloquium: Quantum heat transport in condensed matter systems Jukka P. Pekola and Bayan Karimi Rev. Mod. Phys. 93, 041001 (2021) – Published 5 October 2021 As nanotechnology has led to smaller devices and thermal detectors have become more sensitive, the problem of heat transport in the quantum regime has become more important. Initially driven by theory, the field has expanded in recent years as experiments have become feasible to test these theories. As a result, controlling quantum heat currents and constructing heat engines and related devices on the nanoscale may soon become feasible. This Colloquium discusses these developments from both a fundamental and an applied point of view. Show Abstract PDFHTML 11 citations Irreversible entropy production: From classical to quantum Gabriel T. Landi and Mauro Paternostro Rev. Mod. Phys. 93, 035008 (2021) – Published 24 September 2021 Entropy is a fundamental concept in thermodynamics and statistical physics. It governs processes in physics, chemistry, and biology, and its statistical and information theoretical foundations have been supplemented by recent analyses of fluctuations in microscopic and quantum systems. This article presents a review of theoretical and experimental attempts to describe and assess entropy production in a unified manner from the quantum to the classical level. Show Abstract PDFHTML 4 citations Dark matter annihilation to neutrinos Carlos A. Argüelles, Alejandro Diaz, Ali Kheirandish, Andrés Olivares-Del-Campo, Ibrahim Safa, and Aaron C. Vincent Rev. Mod. Phys. 93, 035007 (2021) – Published 16 September 2021 Astrophysical and cosmological evidence suggests that 85% of the mass in the Universe is not visible. This dark matter has yet to be incorporated into the standard model of particle physics. A leading candidate for dark matter is the weakly interacting massive particle. The production of weakly interacting dark matter in the early Universe implies possible ongoing self-annihilation to the standard model particles wherever dark matter exists today. This article provides a review of probes for the annihilation of dark matter into neutrinos over many orders of magnitude of dark matter mass. It reviews the experimental techniques that are used to detect neutrinos, places updated constraints on the dark matter self-annihilation cross section to neutrinos using recently available data, and forecasts the sensitivity of upcoming neutrino experiments. Show Abstract PDFHTML Wall interactions of spin-polarized atoms Zhen Wu Rev. Mod. Phys. 93, 035006 (2021) – Published 9 September 2021 Experiments with polarized atoms in glass cells show that spin polarization and quantum coherence can survive many collisions of the atoms with the walls, depending on the nature of the wall interactions. This article reviews the physics of the wall interactions of spin-polarized atoms and the experience gained over decades in a field still developing and finding applications in a range of quantum technologies. Show Abstract PDFHTML 7 citations Large-momentum effective theory Xiangdong Ji, Yizhuang Liu, Yu-Sheng Liu, Jian-Hui Zhang, and Yong Zhao Rev. Mod. Phys. 93, 035005 (2021) – Published 30 August 2021 It is an art to match partons defined in the infinite-momentum frame to QCD lattice simulations. Large-momentum effective theory relates properties of Feynman’s partons to partons of finite momentum, using asymptotic freedom to match the former’s properties in the ultraviolet. Finite-momentum partons are then directly matched to nonperturbative QCD quantities. While reviewing recent developments, this article demonstrates its use in extracting physics from a b i n i t i o lattice calculations. Show Abstract PDFHTML 6 citations Baryogenesis from the weak scale to the grand unification scale Dietrich Bödeker and Wilfried Buchmüller Rev. Mod. Phys. 93, 035004 (2021) – Published 19 August 2021 The standard model of elementary particle physics, once augmented with Sakharov’s conditions, offers several scenarios to explain today’s matter-antimatter asymmetry. This survey evaluates the paths to baryogenesis. Of special interest is that time-reversal violation in neutrino physics, together with large mixings, seems poised to produce the observed asymmetry via leptogenesis. This review occurs at a time when several experiments are on the threshold of a precise measurement of time violation in lepton mixing. Show Abstract PDFHTML 7 citations QCD thermalization: Ab initio approaches and interdisciplinary connections Jürgen Berges, Michal P. Heller, Aleksas Mazeliauskas, and Raju Venugopalan Rev. Mod. Phys. 93, 035003 (2021) – Published 4 August 2021 Evidence suggests that terrestrial accelerators can create energy densities yielding a state of matter called the quark-gluon plasma (QGP). The QGP is the result of thermalization in quantum chromodynamics. Terrestrial accelerators collide protons and nuclei where the initial stages of interactions are far out of equilibrium. This review considers two limits: the weak coupling, high occupation limit and the strong coupling limit. While there is much room between these limits, a universal phenomena used to classify these broad descriptions is presented. This also demonstrates connections to strongly correlated systems in atomic and condensed matter physics, in cosmology, and to a holographic correspondence between strongly coupled theories and their gravitational duals. Show Abstract PDFHTML 26 citations The entropy of Hawking radiation Ahmed Almheiri, Thomas Hartman, Juan Maldacena, Edgar Shaghoulian, and Amirhossein Tajdini Rev. Mod. Phys. 93, 035002 (2021) – Published 21 July 2021 This article describes recent progress on the black hole information problem that involves a new understanding of how to calculate the entropy of the Hawking radiation. Show Abstract PDFHTML 4 citations Dynamics of resonant x-ray and Auger scattering Faris Gel’mukhanov, Michael Odelius, Sergey P. Polyutov, Alexander Föhlisch, and Victor Kimberg Rev. Mod. Phys. 93, 035001 (2021) – Published 8 July 2021 With high brightness and tunable resolution, x-ray synchrotron light sources have enhanced the ability to characterize materials. This experimental and theoretical overview of elastic and inelastic x-ray and resonant Auger element-specific scattering processes enabled by these tools provides an updated and comprehensive perspective on electron-nuclear dynamics together with the structural aspects of a broad variety of materials. Materials characterized using these techniques include liquids, gases, molecules, solids with correlated excitations, Mott insulators, and semiconductors. Show Abstract PDFHTML 16 citations CODATA recommended values of the fundamental physical constants: 2018 Eite Tiesinga, Peter J. Mohr, David B. Newell, and Barry N. Taylor Rev. Mod. Phys. 93, 025010 (2021) – Published 30 June 2021 This review article contains the 2018 self-consistent set of values of the constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA). The CODATA values are based on a least-squares adjustment that takes into account all data available up to the end of 2018. Details of the data selection and methodology are described. Show Abstract PDFHTML 12 citations Near-field radiative heat transfer in many-body systems S.-A. Biehs, R. Messina, P. S. Venkataram, A. W. Rodriguez, J. C. Cuevas, and P. Ben-Abdallah Rev. Mod. Phys. 93, 025009 (2021) – Published 16 June 2021 Near-field radiative heat transfer refers to the transport of thermal energy by electromagnetic radiation between objects separated by less than a thermal wavelength. It involves tunneling processes that can lead to large deviations from Planck’s law for blackbody radiation. These problems are of interest at a fundamental level and for devices that exploit heat transport on the nanoscale. This review summarizes the current state of this important field. Show Abstract PDFHTML 6 citations Equilibrium mechanisms of self-limiting assembly Michael F. Hagan and Gregory M. Grason Rev. Mod. Phys. 93, 025008 (2021) – Published 11 June 2021 Self-assembly is a process in which multiple building blocks spontaneously organize into collective and coherent ordered structures. This process is ubiquitous in soft synthetic and biological systems with examples ranging from lipid membranes, surfactant micelles, virus capsids, and bilayer vesicles to multiprotein filaments. This article provides a review on self-limiting assembly, which is the formation and stability of finite-size equilibrium structures, i.e., assemblies that are larger than the size of the building blocks and smaller than macroscopic bulk phases. Show Abstract PDFHTML Vector bosons and jets in proton collisions Paolo Azzurri, Marek Schönherr, and Alessandro Tricoli Rev. Mod. Phys. 93, 025007 (2021) – Published 3 June 2021 Events with vector bosons produced in association with jets have been studied at hadron colliders and provide high-accuracy tests of the standard model. A good understanding of these processes is of paramount importance for precision measurements, including Higgs physics, and for searches for new physics. This review summarizes the theoretical achievements and the state of the art in the modeling of vector-boson-plus-jet physics. It also presents broad experimental results from the Fermilab Tevatron and the CERN LHC colliders and their comparison with the theory. Show Abstract PDFHTML 20 citations Angle-resolved photoemission studies of quantum materials Jonathan A. Sobota, Yu He, and Zhi-Xun Shen Rev. Mod. Phys. 93, 025006 (2021) – Published 26 May 2021 Angle-resolved photoemission (ARPES) has evolved into a precision probe of electronic structure in momentum space of novel quantum materials. This review of a rapidly expanding field summarizes the technical advances leading to an increasing resolution and understanding of quantum materials, including copper- and iron-based superconductors, low-dimensional systems, topological materials, heavy fermions, and many magnetic systems. ARPES is presented as an accessible tool well situated to make advances in our understanding of the electronic structure of novel quantum materials. Show Abstract PDFHTML 53 citations Circuit quantum electrodynamics Alexandre Blais, Arne L. Grimsmo, S. M. Girvin, and Andreas Wallraff Rev. Mod. Phys. 93, 025005 (2021) – Published 19 May 2021 This review surveys the development over the last 15 years of circuit quantum electrodynamics, the nonlinear quantum optics of microwave electrical circuits. In analogy to cavity quantum electrodynamics, lasers are replaced by rf signal generators, optical cavities by superconducting resonators, and atoms by superconducting qubits. Circuit QED offers enhanced light-matter coupling in which strong quantum optical nonlinearities are observable at the level of individual photons. This new parameter regime leads to unique capabilities for fundamental studies in quantum optics, nearly ideal quantum-limited measurements, and quantum computation. Show Abstract PDFHTML 2 citations Emergent constraints on climate sensitivities Mark S. Williamson, Chad W. Thackeray, Peter M. Cox, Alex Hall, Chris Huntingford, and Femke J. M. M. Nijsse Rev. Mod. Phys. 93, 025004 (2021) – Published 11 May 2021 Emergent constraints (ECs) relate observables of the climate system to equivalent quantities simulated from Earth system models that are related to properties of the future climate. The uncertainties in projections of these properties may be reduced by constraining the modeled quantities to observables. The article examines how such relationships emerge from Earth system models, simple theories for how ECs can be derived from temporal variability in the climate system, and how ECs might be misinterpreted. A wide range of ECs discovered so far are presented as well as a framework for quantifying multiple sources of uncertainty in ECs. An outlook for reducing these uncertainties to quantify global environmental change is also given. Show Abstract PDFHTML 30 citations Finite-temperature transport in one-dimensional quantum lattice models B. Bertini, F. Heidrich-Meisner, C. Karrasch, T. Prosen, R. Steinigeweg, and M. Žnidarič Rev. Mod. Phys. 93, 025003 (2021) – Published 5 May 2021 One-dimensional models of interacting electrons have long served as a testing ground for theoretical and numerical methods. More recently they have become directly relevant for interpreting experiments on spin chains, and ultracold quantum gases. This review gives an overview of progress in this important field, with an emphasis on transport properties at nonzero temperatures, covering both theoretical and numerical approaches. Show Abstract