Developing more efficient solar cells has long been a goal of scientists, given the current energy crisis. A theoretical study of black phosphorous, a material useful as an infrared photodetector, shows that it can make a more efficient solar cell in the presence of strain.

[Phys. Rev. X 6, 031046] Published Tue Sep 27, 2016

]]>Probing electronic states on ultrafast timescales is critical for studies of chemical reactions. A tabletop method for performing time-resolved x-ray emission spectroscopy is presented and tested using a polypyridyl iron complex.

[Phys. Rev. X 6, 031047] Published Tue Sep 27, 2016

]]>Quantum computers promise to shed light on many areas of research that have proven too computationally expensive even for current supercomputers. Researchers show how a hybrid quantum-classical approach can be used to simulate strongly correlated materials, such as high-temperature superconductors and transition-metal oxides.

[Phys. Rev. X 6, 031045] Published Wed Sep 21, 2016

]]>A compact scheme can directly modulate the phase of a laser without a bulky external modulator.

[Phys. Rev. X 6, 031044] Published Tue Sep 20, 2016

]]>Bosons and fermions, once thought to be distinct entities, can actually be exchanged via the attachment of flux. This observation is used to relate different theories that have applications in fields as diverse as condensed matter physics and string theory.

[Phys. Rev. X 6, 031043] Published Mon Sep 19, 2016

]]>The structural stability of solar-cell absorbing materials is critical to ensure efficient solar cells. Experiments show how a hybrid perovskite material can be degraded by visible light much more easily than conventional semiconductors such as silicon.

[Phys. Rev. X 6, 031042] Published Thu Sep 15, 2016

]]>Multiqubit measurements will play a vital role in quantum information processing. A new experiment constructs complex measurements on three superconducting qubits and develops important tools toward characterizing them.

[Phys. Rev. X 6, 031041] Published Wed Sep 14, 2016

]]>Error correction is a fundamental aspect of quantum codes. Researchers theoretically show that even 5- and 7-qubit codes can yield universal fault-tolerant computation with relatively low overhead.

[Phys. Rev. X 6, 031039] Published Tue Sep 13, 2016

]]>Superconductors carry current without resistance, but excessive current destroys superconductivity. An investigation of this natural “speed limit” gives a better understanding of the properties of copper-oxide-based, high-temperature superconductors.

[Phys. Rev. X 6, 031040] Published Tue Sep 13, 2016

]]>Networks are everywhere: social networks, linked neurons in the brain, and maps of traffic patterns. A long-standing goal has been to divide networks into relevant “communities,” and now researchers demonstrate a better method for doing so.

[Phys. Rev. X 6, 031038] Published Mon Sep 12, 2016

]]>A newly discovered optical vortex forms a ring around many intense laser pulses but was never noticed before.

[Phys. Rev. X 6, 031037] Published Fri Sep 09, 2016

]]>Communication that relies on quantum carriers, like single photons, can achieve a level of privacy unattainable by classical communication methods. In a new experiment, single microwave photons are used as carriers of quantum information in a manner robust to loss.

[Phys. Rev. X 6, 031036] Published Tue Sep 06, 2016

]]>The interfaces between materials are often rich in physical phenomena such as emergent magnetic properties. A new study analyzes the low-temperature properties of the interface between two oxides controlled by cationic defect formation.

[Phys. Rev. X 6, 031035] Published Tue Aug 30, 2016

]]>Quantum metrology shows that it is always possible to estimate the separation of two stars, no matter how close together they are.

[Phys. Rev. X 6, 031033] Published Mon Aug 29, 2016

]]>In high-dimensional data, where the number of measurements can be far smaller than the number of unknown variables, extracting statistical information can be challenging. Scientists theoretically show how classical statistics can be generalized for such “big data.”

[Phys. Rev. X 6, 031034] Published Mon Aug 29, 2016

]]>Bosonic optoelectronic excitations known as polaritons may play crucial roles in futuristic quantum technologies. Researchers investigate the phase coupling between coherent quantum states of polaritons held at roughly 10 degrees above absolute zero.

[Phys. Rev. X 6, 031032] Published Fri Aug 26, 2016

]]>Inducing superconductivity in the surface of a three-dimensional topological insulator has long been a goal of condensed-matter physics. A new experiment realizes this process in a thin film of samarium hexaboride.

[Phys. Rev. X 6, 031031] Published Thu Aug 25, 2016

]]>Superconductivity is a fascinating property in which electrical resistance drops to zero. An investigation into the energy stored in the long-range Coulomb interaction in cuprates furthers understanding of these materials’ high-temperature superconductivity.

[Phys. Rev. X 6, 031027] Published Wed Aug 24, 2016

]]>Light-matter interactions play critical roles in many areas of physics. A new study shows how the paths of electrons liberated from molecules can be effectively measured to extremely high temporal and spatial resolutions.

[Phys. Rev. X 6, 031029] Published Wed Aug 24, 2016

]]>Noise is a fundamental aspect of experimental procedures, and achieving reliable quantum computing requires compensating for errors. Scientists show that certain types of errors can be calibrated out in a 7-qubit quantum error-correcting code in a system of trapped ions.

[Phys. Rev. X 6, 031030] Published Wed Aug 24, 2016

]]>Some of the remarkable behaviors of strongly correlated metals may be controlled by quantum phase transitions. An exact numerical method is used to reveal the properties of a model exhibiting a quantum phase transition between an isotropic and a nematic metal.

[Phys. Rev. X 6, 031028] Published Tue Aug 23, 2016

]]>Quantum information processing of the future may rely on controlling systems of interacting atoms or ions. A theoretical proposal shows how a lattice of ionic crystals can demonstrate critical phases that are neither fully disordered nor fully ordered.

[Phys. Rev. X 6, 031025] Published Mon Aug 22, 2016

]]>Differentiating between Dirac composite fermions and the Halperin-Lee-Read state has long been difficult. Now, a theoretical demonstration shows that the Nernst effect—a type of thermoelectric transport measurement—can be used to test the Dirac nature of composite fermions.

[Phys. Rev. X 6, 031026] Published Mon Aug 22, 2016

]]>A progressive loss of phase information (i.e., decoherence) is fundamental to many physical systems since they evolve over time. Researchers present a way of deriving master equations to dynamically characterize disordered quantum systems with finite dimensions.

[Phys. Rev. X 6, 031023] Published Fri Aug 19, 2016

]]>The central nervous system is a prime example of a complex network. Scientists derive the statistics associated with the interactions between pairs of binary units representing individual neurons.

[Phys. Rev. X 6, 031024] Published Fri Aug 19, 2016

]]>Researchers provide new evidence for the existence of type-II Weyl semimetals, which would be both conducting and insulating in different spatial directions.

[Phys. Rev. X 6, 031021] Published Wed Aug 17, 2016

]]>Observing the effects of quantum phenomena requires relatively long state lifetimes. In a new experiment, ultracold dysprosium atoms are used to demonstrate that spin-orbit coupling persists for 10 to 100 times longer than in other atoms.

[Phys. Rev. X 6, 031022] Published Wed Aug 17, 2016

]]>A Rydberg atom immersed in a dense cloud of ultracold neutral atoms can undergo two chemical processes.

[Phys. Rev. X 6, 031020] Published Wed Aug 10, 2016

]]>Majorana particles are favored in quantum computing, which promises exponential increases in processing speed compared with classical protocols. Now, researchers propose using Majoranas to perform a magic gate that is more resistant to system noise.

[Phys. Rev. X 6, 031019] Published Mon Aug 08, 2016

]]>Pulses of light are made up of quantum particles called photons. A novel way of making individual photons interact could pave the way toward generating photonic “molecules” and even more complex states of light.

[Phys. Rev. X 6, 031017] Published Thu Aug 04, 2016

]]>The field of gravitational-wave astronomy celebrated its first direct detection of a binary black hole merger in 2015. Researchers study what can and cannot be learned through observations of the stochastic background of distant gravitational-wave signals.

[Phys. Rev. X 6, 031018] Published Thu Aug 04, 2016

]]>Preparing, manipulating, and reading out Majorana zero modes is important for quantum computing. A theoretically developed set of milestone experiments, if conducted successfully, may pave the way for fault-tolerant “topological” quantum information processing.

[Phys. Rev. X 6, 031016] Published Wed Aug 03, 2016

]]>Quantum annealing is a quantum enhanced heuristic optimization algorithm that exploits quantum tunneling. New work shows that it can significantly outperform its classical analog (simulated annealing) as well as the most popular classical algorithm for simulating quantum annealing (quantum Monte Carlo).

[Phys. Rev. X 6, 031015] Published Mon Aug 01, 2016

]]>A chiral object cannot be superimposed onto its mirror image—a geometric definition of chirality. A new theoretical study introduces a definition of electromagnetic chirality.

[Phys. Rev. X 6, 031013] Published Thu Jul 28, 2016

]]>Sensing magnetic fields is a key aspect in many areas of study such as biomedical imaging and geophysics. Researchers demonstrate all-optical solid-state magnetometry that is sensitive to magnetic fields weaker than 100 nT.

[Phys. Rev. X 6, 031014] Published Thu Jul 28, 2016

]]>Phase transitions are ubiquitous in nature and can occur in out-of-equilibrium situations. The key role of short-range fluctuations in dissipative phase transitions is theoretically demonstrated and can be experimentally reproduced in the future using trapped ions, Rydberg states of atoms, or microwave circuits.

[Phys. Rev. X 6, 031011] Published Wed Jul 27, 2016

]]>Metals, semiconductors, and insulators all exhibit the spin Seebeck effect, in which a temperature gradient results in current flow. Now, researchers advance our understanding of how the spin Seebeck effect depends on temperature and material properties.

[Phys. Rev. X 6, 031012] Published Wed Jul 27, 2016

]]>It is commonly believed that quantum tunneling is necessary for a quantum speedup in quantum annealing, but a theoretical demonstration shows that quantum tunneling is not always the most efficient way to yield a quantum speedup.

[Phys. Rev. X 6, 031010] Published Thu Jul 21, 2016

]]>Complex networks like neural maps and the internet are characterized by a large number of connected nodes. A new algorithm shows how three-dimensional networks can be computationally simplified by tiling an abstract surface.

[Phys. Rev. X 6, 031009] Published Wed Jul 20, 2016

]]>[Phys. Rev. X 6, 039901] Published Tue Jul 19, 2016

]]>A quantum computer is used to efficiently model a quantum chemical system to extremely high accuracy.

[Phys. Rev. X 6, 031007] Published Mon Jul 18, 2016

]]>Obtaining large quantities of drinkable water via desalinization is often an expensive, complex process. A theoretical method for obtaining clean water from waste is presented, drawing on inspiration from the human kidney.

[Phys. Rev. X 6, 031008] Published Mon Jul 18, 2016

]]>Optimal quantum error-correction codes are necessary to extend the lifetime of quantum memories. A new error-correction code to rectify photon loss, gain, and dephasing errors in electromagnetic cavities is presented.

[Phys. Rev. X 6, 031006] Published Thu Jul 14, 2016

]]>Dynamic networks are common in complex systems, and coarse-graining their evolving structure is a key step to understanding them. General mathematical tools for identifying the theoretical limits of such methods are presented.

[Phys. Rev. X 6, 031005] Published Wed Jul 13, 2016

]]>By bathing a superconducting qubit in squeezed light, researchers have been able to confirm a decades-old prediction for the resulting phase-dependent spectrum of resonance fluorescence.

[Phys. Rev. X 6, 031004] Published Mon Jul 11, 2016

]]>Quasiparticles with no direct analogs in the standard model have been recently revealed in experiments. Researchers theoretically analyze the physical properties of triple point fermions, which can be thought of as a melding of Dirac and Weyl fermions.

[Phys. Rev. X 6, 031003] Published Thu Jul 07, 2016

]]>In quantum circuits, electrical fluctuations render the behavior of the components interdependent, calling for new circuit rules. Now, researchers establish such rules for simple quantum components.

[Phys. Rev. X 6, 031002] Published Tue Jul 05, 2016

]]>Cells that are electrically active and that also produce light for easy voltage monitoring could lead to new studies of heart arrhythmias and possibly bio-computing.

[Phys. Rev. X 6, 031001] Published Fri Jul 01, 2016

]]>A scanning probe detects the quantum states of photons in a microwave circuit, providing the information needed for quantum simulations.

[Phys. Rev. X 6, 021044] Published Thu Jun 30, 2016

]]>Solid-state materials are invariably plagued by disorder in real-world experiments. In a numerical study, researchers investigate the semimetal phases of Dirac and Weyl semimetals characterized by disorder.

[Phys. Rev. X 6, 021042] Published Wed Jun 29, 2016

]]>Hybrid quantum-classical computation may be a hallmark of future technologies. Researchers investigate the tradeoff between employing quantum and classical resources for computational tasks.

[Phys. Rev. X 6, 021043] Published Wed Jun 29, 2016

]]>Entanglement purification, a vital enabler for practical quantum networks, has been shown to be feasible with secluded nuclear memories in diamond.

[Phys. Rev. X 6, 021040] Published Wed Jun 22, 2016

]]>Current liquid-crystal research will pave the way for next-generation electro-optical displays. Researchers experimentally and theoretically characterize the fluctuation modes of a new phase of liquid crystals.

[Phys. Rev. X 6, 021041] Published Wed Jun 22, 2016

]]>The intrinsic electric field that exists in certain classes of materials plays a key role in many fields of electronics. Researchers reveal and correct a shortcoming in the way that the electric polarization has been modeled in a technologically important class of these materials.

[Phys. Rev. X 6, 021038] Published Mon Jun 20, 2016

]]>Richard Feynman suggested that it takes a quantum computer to simulate large quantum systems, but a new study shows that a classical computer can work when the system has loss and noise.

[Phys. Rev. X 6, 021039] Published Mon Jun 20, 2016

]]>Intense X-ray free electron laser pulses can completely obliterate molecules, but the process also sheds light on the energetic ions that are created. Researchers experimentally and theoretically investigate how 5-iodouacil responds to x-ray free electron laser radiation.

[Phys. Rev. X 6, 021035] Published Thu Jun 16, 2016

]]>Evolutionary adaptation is commonly thought of as arising from reproduction. A new thermodynamic perspective on self-organization far from thermal equilibrium links the biological world and other systems governed by the same general physical principles.

[Phys. Rev. X 6, 021036] Published Thu Jun 16, 2016

]]>Systems of interacting photons are an intriguing arena for studying nonequilibrium many-body physics. Researchers theoretically investigate computational tools to validate experimental data and pave the way for studies using quantum simulators.

[Phys. Rev. X 6, 021037] Published Thu Jun 16, 2016

]]>Next-generation energy technologies may rely on nanoporous supercapacitors for storing energy. Simulations and theoretical analysis are used to determine how to achieve the highest possible capacitance in supercapacitors.

[Phys. Rev. X 6, 021034] Published Tue Jun 14, 2016

]]>New simulations of an alternate fusion reactor design reveal that it can be stable against turbulent fluctuations.

[Phys. Rev. X 6, 021033] Published Tue Jun 07, 2016

]]>Explaining high-temperature superconductivity relies on understanding the degrees of freedom present in electronic states. A theoretical investigation shows how rotational symmetry can be violated in FeSe.

[Phys. Rev. X 6, 021032] Published Fri Jun 03, 2016

]]>Understanding the speed with which a quantum system can evolve between distinguishable states has applications in quantum technology. A new theoretical study demonstrates a general family of quantum speed limits that can be applied to any physical process.

[Phys. Rev. X 6, 021031] Published Thu Jun 02, 2016

]]>The Mott metal-to-insulator transition is an important phenomenon in condensed matter physics. Researchers take a direct look at this transition, using ytterbium atoms in an optical lattice to realize an extended-symmetry insulator, to better understand fermionic many-body systems.

[Phys. Rev. X 6, 021030] Published Wed Jun 01, 2016

]]>Intrinsic noise is unavoidable in quantum devices and represents a hindrance to implementing quantum computation. Despite the presence of noise, a quantum-annealing algorithm that involves quantum tunneling may provide computational advantages over simulated annealing.

[Phys. Rev. X 6, 021028] Published Tue May 31, 2016

]]>Superconductivity is the phenomenon in which, below a certain temperature, a metal loses all resistance to current flow. Using a simple model, theorists show that it is possible to drive a fermionic band insulator into a superconductor.

[Phys. Rev. X 6, 021029] Published Tue May 31, 2016

]]>An impurity and a bath of free bosons can be coupled, which results in the impurity trapping the bosons. Researchers use exact and numerical calculations to parametrize this phenomenon.

[Phys. Rev. X 6, 021027] Published Wed May 25, 2016

]]>A predicted type of atom-light crystal could host phonon-like excitations, allowing for new ways to simulate the physics of solids.

[Phys. Rev. X 6, 021026] Published Tue May 24, 2016

]]>A recently discovered class of two-dimensional semiconductors exhibits a novel degree of freedom known as valley pseudospin. New results show that a weak magnetic field can significantly extend the depolarization time of this pseudospin.

[Phys. Rev. X 6, 021024] Published Fri May 20, 2016

]]>Dilute atomic gases with tunable interactions are tools that can be used to understand many-body physics. Scientists study the interplay between two-body evaporation and three-body recombination in ultracold cesium and lithium gases.

[Phys. Rev. X 6, 021025] Published Fri May 20, 2016

]]>Motors that perform work can be powered by either a chemical fuel or time-dependent changes in their surrounding environment. A theoretical analysis shows that these two classes of motors are thermodynamically equivalent.

[Phys. Rev. X 6, 021022] Published Wed May 18, 2016

]]>Recurrent neuronal networks constitute the biological substrate of high-level brain functions such as memory and reasoning. Researchers use energy-efficient, neurally inspired hardware to show how network heterogeneity affects the dynamics of such systems.

[Phys. Rev. X 6, 021023] Published Wed May 18, 2016

]]>Collision and transport phenomena are difficult to describe in many dense, strongly interacting laboratory and astrophysical plasmas. Now, researchers experimentally study collisional dynamics in dilute plasmas of ${}^{88}$Sr ions barely one degree above absolute zero.

[Phys. Rev. X 6, 021021] Published Tue May 17, 2016

]]>The internet is filled with memes that have “gone viral.” A study of meme popularity uses an analytically tractable model that sheds light on the fundamental drivers of meme popularity in social networks.

[Phys. Rev. X 6, 021019] Published Fri May 13, 2016

]]>X-ray photons can be used as unique probes to understand the properties of elementary excitations. A theoretical study demonstrates that a complex x-ray scattering technique captures richer spectral information than simpler two-particle correlation functions in cuprate superconductors.

[Phys. Rev. X 6, 021020] Published Fri May 13, 2016

]]>In quantum mechanics, Heisenberg’s uncertainty principle prevents the determination of precise, simultaneous measurements of two quantities. A new approach extracts position and momentum information from the same group of entangled photons by dramatically undersampling the system.

[Phys. Rev. X 6, 021018] Published Thu May 12, 2016

]]>Free-space laser links have been used to synchronize optical clocks with an unprecedented uncertainty of femtoseconds.

[Phys. Rev. X 6, 021016] Published Wed May 11, 2016

]]>Topological edge states are observed inside a large band gap on the surface of ZrTe${}_{5}$ crystals, paving the way for topological quantum computing devices.

[Phys. Rev. X 6, 021017] Published Tue May 10, 2016

]]>Microwave cavities are widely used to control closed few-level systems in the context of quantum information processing. Now, they also appear as a powerful probe for quantum tunneling in hybrid nanocircuits.

[Phys. Rev. X 6, 021014] Published Mon May 09, 2016

]]>Linking the properties of a material’s bulk and surface is often challenging and limited to low-dimensional systems. Now, researchers theoretically demonstrate a bulk-boundary correspondence for a class of three-dimensional insulators, namely symmetry-protected topological phases of matter.

[Phys. Rev. X 6, 021015] Published Mon May 09, 2016

]]>Researchers discover a unique topological phase present in a periodically driven, two-dimensional system: All of its bulk Floquet states are localized by disorder while its edges support propagating chiral modes.

[Phys. Rev. X 6, 021013] Published Fri May 06, 2016

]]>[Phys. Rev. X 6, 020001] Published Wed May 04, 2016

]]>[Phys. Rev. X 6, 029902] Published Tue May 03, 2016

]]>Shining a laser onto a microscopic object coated with a superfluid film induces flows that can generate a controlled force.

[Phys. Rev. X 6, 021012] Published Fri Apr 29, 2016

]]>Understanding metastatic cell escape from tumors and embryonic development requires a detailed understanding of how cells move collectively inside dense tissues. Scientists show that small changes to single-cell behavior can cause tissue to transition between a fluidlike and a solidlike state.

[Phys. Rev. X 6, 021011] Published Thu Apr 21, 2016

]]>[Phys. Rev. X 6, 029901] Published Tue Apr 19, 2016

]]>Topological insulators combine aspects of metals, semiconductors, and insulators and also show unusual electric properties. A theoretical study reveals that they also exhibit unconventional magnetism as a result of electron transitions normally forbidden by energy conservation.

[Phys. Rev. X 6, 021010] Published Mon Apr 18, 2016

]]>Naturally occurring crystals are classified by spacetime symmetries, and now researchers theoretically expand this classification, with the aim of topologically classifying band insulators.

[Phys. Rev. X 6, 021008] Published Fri Apr 15, 2016

]]>A mathematical technique for comparing large symbol sets suggests that less frequently used words are mainly responsible for the evolution of the English language over the past two centuries.

[Phys. Rev. X 6, 021009] Published Fri Apr 15, 2016

]]>An investigation into how lipids diffuse in the presence of varying protein:lipid number ratios reveals that protein crowding results in drastically different lipid and protein diffusion due to the strengthened impact of correlated motion.

[Phys. Rev. X 6, 021006] Published Tue Apr 12, 2016

]]>Understanding the physics in multiple-state open systems is critical in many fields of physics. A study of an ensemble of connected lossy cavities shows how eigenstates can coalesce to produce new higher-order singularities.

[Phys. Rev. X 6, 021007] Published Tue Apr 12, 2016

]]>Fault-tolerant topological quantum computation has long been a goal of physicists. A theoretical proposal shows how Majorana zero modes can be used in a universal quantum computer in a manner that avoids precise timing requirements.

[Phys. Rev. X 6, 021005] Published Fri Apr 08, 2016

]]>Interactions between atomic ions and valence electrons are fundamental to the properties of all materials. A new investigation visualizes and quantifies electron-lattice interactions in aluminum heated by an infrared laser pulse.

[Phys. Rev. X 6, 021003] Published Wed Apr 06, 2016

]]>High-temperature superconductivity in cuprates is an ongoing mystery. Scientists show that two electronic phases of the cuprate La${}_{2-x}$Sr${}_{x}$CuO${}_{4}$ are in fact separate.

[Phys. Rev. X 6, 021004] Published Wed Apr 06, 2016

]]>Accurately measuring extremely small forces is important in many fields of physics, materials science, and engineering. Researchers demonstrate tiny “trampoline’’ mechanical sensors that are exquisitely sensitive to attonewton forces at room temperature.

[Phys. Rev. X 6, 021001] Published Fri Apr 01, 2016

]]>Modern society is permeated by systems with many numbers of nodes and connections (e.g., rail networks, airports). A theoretical study of the multiplex network consisting of European Union air routes and the London rail transportation system demonstrates the fragility of such a network.

[Phys. Rev. X 6, 021002] Published Fri Apr 01, 2016

]]>An analysis of data spanning 29 orders of magnitude in gravitational-wave frequency provides insights into the physics of the early cosmos.

[Phys. Rev. X 6, 011035] Published Thu Mar 31, 2016

]]>Multiple interaction layers are a fact of life in real-world networks. Scientists model how well networks can be represented using superpositions of layers assembled using either AND or OR logic.

[Phys. Rev. X 6, 011036] Published Thu Mar 31, 2016

]]>Studies of molecular motors and their cargo moving within cells have revealed that they can be trapped for long periods of times. Researchers show that this trapping can occur when the motors encounter intersections of cytoskeletal filaments within cells.

[Phys. Rev. X 6, 011037] Published Thu Mar 31, 2016

]]>A variety of linelike structures in orientationally ordered materials are identified by researchers as umbilic lines, a natural set of geometric singularities that reveal the topological structure of these materials.

[Phys. Rev. X 6, 011033] Published Mon Mar 28, 2016

]]>$U(1)$ quantum spin liquids represent quantum phases of matter associated with different electric and magnetic particles. A theoretical study shows how these phases can be distinguished in the presence of time-reversal symmetry.

[Phys. Rev. X 6, 011034] Published Mon Mar 28, 2016

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