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NEWSPAPER Behavior of an active nematic droplet with increasing activity (left to right). The more active the droplet, the more it deforms, until it splits. [Luca Giomi and Antonio DeSimone, Phys. Rev. Lett. 114, 147802 (2014)]

PHYSICAL REVIEW LETTERSä Contents Articles published 5 April–11 April 2014

VOLUME 112, NUMBER 14 11 April 2014

General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. Experimental Tests of Classical and Quantum Dimensionality ...... 140401 Johan Ahrens, Piotr Badziąg, Marcin Pawłowski, Marek Żukowski, and Mohamed Bourennane Certifying Separability in Symmetric Mixed States of N Qubits, and Superradiance ...... 140402 Elie Wolfe and S. F. Yelin Coherent Backscattering in Fock Space: A Signature of Quantum Many-Body Interference in Interacting Bosonic Systems 140403 Thomas Engl, Julien Dujardin, Arturo Argüelles, Peter Schlagheck, Klaus Richter, and Juan Diego Urbina Test of Genuine Multipartite Nonlocality without Inequalities ...... 140404 Qing Chen, Sixia Yu, Chengjie Zhang, C. H. Lai, and C. H. Oh On-Demand Dark Soliton Train Manipulation in a Spinor Polariton Condensate ...... 140405 F. Pinsker and H. Flayac Amplification, Redundancy, and Quantum Chernoff Information ...... 140406 Michael Zwolak, C. Jess Riedel, and Wojciech H. Zurek Certifying the Dimension of Classical and Quantum Systems in a Prepare-and-Measure Scenario with Independent Devices 140407 Joseph Bowles, Marco Túlio Quintino, and Nicolas Brunner Quantum Criticality and Dynamical Instability in the Kicked-Top Model ...... 140408 Victor Manuel Bastidas, Pedro Pérez-Fernández, Malte Vogl, and Tobias Brandes Experimental Entanglement Activation from Discord in a Programmable Quantum Measurement ...... 140501 Gerardo Adesso, Vincenzo D’Ambrosio, Eleonora Nagali, Marco Piani, and Fabio Sciarrino How Energy Conservation Limits Our Measurements ...... 140502 Miguel Navascués and Sandu Popescu Device-Independent Certification of High-Dimensional Quantum Systems ...... 140503 Vincenzo D’Ambrosio, Fabrizio Bisesto, Fabio Sciarrino, Johanna F. Barra, Gustavo Lima, and Adán Cabello Asymptotically Optimal Topological Quantum Compiling ...... 140504 Vadym Kliuchnikov, Alex Bocharov, and Krysta M. Svore Measurement-Based Classical Computation ...... 140505 Matty J. Hoban, Joel J. Wallman, Hussain Anwar, Naïri Usher, Robert Raussendorf, and Dan E. Browne Implementation of a Measurement-Device-Independent Entanglement Witness ...... 140506 Ping Xu, Xiao Yuan, Luo-Kan Chen, He Lu, Xing-Can Yao, Xiongfeng Ma, Yu-Ao Chen, and Jian-Wei Pan Can Communication Power of Separable Correlations Exceed That of Entanglement Resource? ...... 140507 Paweł Horodecki, Jan Tuziemski, Paweł Mazurek, and Ryszard Horodecki Classical Nernst engine ...... 140601 Julian Stark, Kay Brandner, Keiji Saito, and Udo Seifert Nonequilibrium Fluctuation-Dissipation Theorem and Heat Production ...... 140602 E. Lippiello, M. Baiesi, and A. Sarracino Parallelized Quantum Monte Carlo Algorithm with Nonlocal Worm Updates ...... 140603 Akiko Masaki-Kato, Takafumi Suzuki, Kenji Harada, Synge Todo, and Naoki Kawashima

(Continued Inside) Selected for a Viewpoint in Physics. Please visit http://physics.aps.org/. By suggesting a few manuscripts each week, we hope to promote reading across fields. Please see our Announcement Phys. Rev. Lett. 98, 010001 (2007).

0031-9007(20140411)112:14;1-Y Contents (Continued)

Elementary Particles and Fields Conformal Field Theories in Fractional Dimensions ...... 141601 Sheer El-Showk, Miguel Paulos, David Poland, Slava Rychkov, David Simmons-Duffin, and Alessandro Vichi Topological Response Theory of Abelian Symmetry-Protected Topological Phases in Two Dimensions ...... 141602 Meng Cheng and Zheng-Cheng Gu Pion Masses in Two-Flavor QCD with η Condensation ...... 141603 Sinya Aoki and Michael Creutz High-Precision Predictions for the Light CP-Even Higgs Boson Mass of the Minimal Supersymmetric Standard Model 141801 T. Hahn, S. Heinemeyer, W. Hollik, H. Rzehak, and G. Weiglein Photoproduction of π0 Mesons off Neutrons in the Nucleon Resonance Region ...... 142001 M. Dieterle et al. (Crystal Ball/TAPS experiment at MAMI, A2 Collaboration)

Nuclear Physics Deformation-Driven p-Wave Halos at the Drip Line: 31Ne ...... 142501 T. Nakamura, N. Kobayashi, Y. Kondo, Y. Satou, J. A. Tostevin, Y. Utsuno, N. Aoi, H. Baba, N. Fukuda, J. Gibelin, N. Inabe, M. Ishihara, D. Kameda, T. Kubo, T. Motobayashi, T. Ohnishi, N. A. Orr, H. Otsu, T. Otsuka, H. Sakurai, T. Sumikama, H. Takeda, E. Takeshita, M. Takechi, S. Takeuchi, Y. Togano, and K. Yoneda Evolution of Collectivity in 72Kr: Evidence for Rapid Shape Transition ...... 142502 H. Iwasaki, A. Lemasson, C. Morse, A. Dewald, T. Braunroth, V. M. Bader, T. Baugher, D. Bazin, J. S. Berryman, C. M. Campbell, A. Gade, C. Langer, I. Y. Lee, C. Loelius, E. Lunderberg, F. Recchia, D. Smalley, S. R. Stroberg, R. Wadsworth, C. Walz, D. Weisshaar, A. Westerberg, K. Whitmore, and K. Wimmer Neutrino Propagation in Nuclear Medium and Neutrinoless Double-β Decay ...... 142503 S. Kovalenko, M. I. Krivoruchenko, and F. Šimkovic

Atomic, Molecular, and Optical Physics Dynamic Dimensionality Identification for Quantum Control ...... 143001 Jonathan Roslund and Herschel Rabitz Fermionic Superradiance in a Transversely Pumped Optical Cavity ...... 143002 J. Keeling, M. J. Bhaseen, and B. D. Simons Umklapp Superradiance with a Collisionless Quantum Degenerate Fermi Gas ...... 143003 Francesco Piazza and Philipp Strack Superradiance of Degenerate Fermi Gases in a Cavity ...... 143004 Yu Chen, Zhenhua Yu, and Hui Zhai Double Photoionization in Ring Molecules: Search of the Cooper Pair Formation ...... 143005 K. Jänkälä, P. Lablanquie, F. Penent, J. Palaudoux, L. Andric, and M. Huttula Ionization of Excited Atoms by Intense Single-Cycle THz Pulses ...... 143006 Sha Li and R. R. Jones Bose-Einstein Condensates with Cavity-Mediated Spin-Orbit Coupling ...... 143007 Y. Deng, J. Cheng, H. Jing, and S. Yi Alignment of D-State Rydberg Molecules ...... 143008 A. T. Krupp, A. Gaj, J. B. Balewski, P. Ilzhöfer, S. Hofferberth, R. Löw, T. Pfau, M. Kurz, and P. Schmelcher Neutral Gas Sympathetic Cooling of an Ion in a Paul Trap ...... 143009 Kuang Chen, Scott T. Sullivan, and Eric R. Hudson Microscopic Superfluidity in 4He Clusters Stirred by a Rotating Impurity Molecule ...... 143401 Angeline Wairegi, Antonio Gamboa, Andrew D. Burbanks, Ernestine A. Lee, and David Farrelly Quantum Control of Molecular Gas Hydrodynamics ...... 143601 S. Zahedpour, J. K. Wahlstrand, and H. M. Milchberg Heralded Single-Phonon Preparation, Storage, and Readout in Cavity Optomechanics ...... 143602 Christophe Galland, Nicolas Sangouard, Nicolas Piro, Nicolas Gisin, and Tobias J. Kippenberg Observation of Entanglement-Dependent Two-Particle Holonomic Phase ...... 143603 J. C. Loredo, M. A. Broome, D. H. Smith, and A. G. White

(Continued on Preceding Page) Selected for a Viewpoint in Physics. Please visit http://physics.aps.org/. By suggesting a few manuscripts each week, we hope to promote reading across fields. Please see our Announcement Phys. Rev. Lett. 98, 010001 (2007) Contents (Continued)

Quantum Walks of Correlated Photon Pairs in Two-Dimensional Waveguide Arrays ...... 143604 Konstantinos Poulios, Robert Keil, Daniel Fry, Jasmin D. A. Meinecke, Jonathan C. F. Matthews, Alberto Politi, Mirko Lobino, Markus Gräfe, Matthias Heinrich, Stefan Nolte, Alexander Szameit, and Jeremy L. O’Brien

Nonlinear Dynamics, Fluid Dynamics, Classical Optics, etc. Light Transport and Localization in Two-Dimensional Correlated Disorder ...... 143901 Gaurasundar M. Conley, Matteo Burresi, Filippo Pratesi, Kevin Vynck, and Diederik S. Wiersma Macroscopic Effects in Noncollinear High-Order Harmonic Generation ...... 143902 C. M. Heyl, P. Rudawski, F. Brizuela, S. N. Bengtsson, J. Mauritsson, and A. L’Huillier Experimental Demonstration of a Coherent Perfect Absorber with PT Phase Transition ...... 143903 Yong Sun, Wei Tan, Hong-qiang Li, Jensen Li, and Hong Chen Laboratory Demonstration of Spatial-Coherence Analysis of a Blackbody through an Up-Conversion Interferometer .... 143904 J.-T. Gomes, L. Delage, R. Baudoin, L. Grossard, L. Bouyeron, D. Ceus, F. Reynaud, H. Herrmann, and W. Sohler Chimera States: The Existence Criteria Revisited ...... 144101 Gautam C. Sethia and Abhijit Sen Universal Quantum Graphs ...... 144102 Z. Pluhař and H. A. Weidenmüller Chimeralike States in an Ensemble of Globally Coupled Oscillators ...... 144103 Azamat Yeldesbay, Arkady Pikovsky, and Michael Rosenblum Negative Refraction and Energy Funneling by Hyperbolic Materials: An Experimental Demonstration in Acoustics ..... 144301 Victor M. García-Chocano, Johan Christensen, and José Sánchez-Dehesa Upscale Energy Transfer in Three-Dimensional Rapidly Rotating Turbulent Convection ...... 144501 Antonio M. Rubio, Keith Julien, Edgar Knobloch, and Jeffrey B. Weiss Recurrent Bursts via Linear Processes in Turbulent Environments ...... 144502 Geert Brethouwer, Philipp Schlatter, Yohann Duguet, Dan S. Henningson, and Arne V. Johansson Surface Nanobubbles Nucleate Microdroplets ...... 144503 Xuehua Zhang, Henri Lhuissier, Chao Sun, and Detlef Lohse Shock-Wave Compression and Joule-Thomson Expansion ...... 144504 Wm. G. Hoover, Carol G. Hoover, and Karl P. Travis Numerical Simulation of a Self-Similar Cascade of Filament Instabilities in the Surface Quasigeostrophic System ...... 144505 R. K. Scott and D. G. Dritschel

Plasma and Beam Physics Nonuniformly Driven Two-Plasmon-Decay Instability in Direct-Drive Implosions ...... 145001 W. Seka, J. F. Myatt, R. W. Short, D. H. Froula, J. Katz, V. N. Goncharov, and I. V. Igumenshchev Čerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection ...... 145002 M. V. Goldman, D. L. Newman, G. Lapenta, L. Andersson, J. T. Gosling, S. Eriksson, S. Markidis, J. P. Eastwood, and R. Ergun Radiation-Reaction Trapping of Electrons in Extreme Laser Fields ...... 145003 L. L. Ji, A. Pukhov, I. Yu. Kostyukov, B. F. Shen, and K. Akli Observations of Continuum Depression in Warm Dense Matter with X-Ray Thomson Scattering ...... 145004 L. B. Fletcher, A. L. Kritcher, A. Pak, T. Ma, T. Döppner, C. Fortmann, L. Divol, O. S. Jones, O. L. Landen, H. A. Scott, J. Vorberger, D. A. Chapman, D. O. Gericke, B. A. Mattern, G. T. Seidler, G. Gregori, R. W. Falcone, and S. H. Glenzer Electron-Ion Equilibration in Ultrafast Heated Graphite ...... 145005 T. G. White, N. J. Hartley, B. Borm, B. J. B. Crowley, J. W. O. Harris, D. C. Hochhaus, T. Kaempfer, K. Li, P. Neumayer, L. K. Pattison, F. Pfeifer, S. Richardson, A. P. L. Robinson, I. Uschmann, and G. Gregori Direct Detection of Resonant Electron Pitch Angle Scattering by Whistler Waves in a Laboratory Plasma ...... 145006 B. Van Compernolle, J. Bortnik, P. Pribyl, W. Gekelman, M. Nakamoto, X. Tao, and R. M. Thorne Ab Initio Simulations for the Ion-Ion Structure Factor of Warm Dense Aluminum ...... 145007 Hannes R. Rüter and Ronald Redmer

Optically Controlled Solid-Density Transient Plasma Gratings ...... 145008 S. Monchocé, S. Kahaly, A. Leblanc, L. Videau, P. Combis, F. Réau, D. Garzella, P. D’Oliveira, Ph. Martin, and F. Quéré

Condensed Matter: Structure, etc. Onsager-Kraichnan Condensation in Decaying Two-Dimensional Quantum Turbulence ...... 145301 T. P. Billam, M. T. Reeves, B. P. Anderson, and A. S. Bradley Finite Size Analysis of Zero-Temperature Jamming Transition under Applied Shear Stress by Minimizing a Thermodynamic-Like Potential ...... 145502 Hao Liu, Xiaoyi Xie, and Ning Xu Fermi-Pasta-Ulam Physics with Nanomechanical Graphene Resonators: Intrinsic Relaxation and Thermalization from Flexural Mode Coupling ...... 145503 Daniel Midtvedt, Alexander Croy, Andreas Isacsson, Zenan Qi, and Harold S. Park Plasticity Initiation and Evolution during Nanoindentation of an Iron–3% Silicon Crystal ...... 145504 Ling Zhang and Takahito Ohmura Glass Transitions in a Monatomic Liquid with Two Glassy States ...... 145701 Andrew Gordon and Nicolas Giovambattista Relationships between Atomic Diffusion Mechanisms and Ensemble Transport Coefficients in Crystalline Polymorphs 145901 Benjamin J. Morgan and Paul A. Madden Effects of Rotational-Symmetry Breaking on Physisorption of Ortho- and Para-H2 on Ag(111) ...... 146101 Toshiki Sugimoto and Katsuyuki Fukutani Wetting of Elastic Solids on Nanopillars ...... 146102 M. Ignacio, Y. Saito, P. Smereka, and O. Pierre-Louis Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum ...... 146103 Jakub D. Baran, Henrik Grönbeck, and Anders Hellman

Condensed Matter: Electronic Properties, etc. First-Principles Calculation of Atomic Forces and Structural Distortions in Strongly Correlated Materials ...... 146401 I. Leonov, V. I. Anisimov, and D. Vollhardt Coexistence of Spin Density Waves and Superconductivity in ðTMTSFÞ2PF6 ...... 146402 Arjun Narayanan, Andhika Kiswandhi, David Graf, James Brooks, and Paul Chaikin Inducing a Lifshitz Transition by Extrinsic Doping of Surface Bands in the Topological Crystalline Insulator Pb1−xSnxSe 146403 I. Pletikosić, G. D. Gu, and T. Valla Fractal Energy Spectrum of a Polariton Gas in a Fibonacci Quasiperiodic Potential ...... 146404 D. Tanese, E. Gurevich, F. Baboux, T. Jacqmin, A. Lemaître, E. Galopin, I. Sagnes, A. Amo, J. Bloch, and E. Akkermans Time Reversal Symmetric Topological Exciton Condensate in Bilayer HgTe Quantum Wells ...... 146405 Jan Carl Budich, Björn Trauzettel, and Paolo Michetti Finite-Temperature Conductivity and Magnetoconductivity of Topological Insulators ...... 146601 Hai-Zhou Lu and Shun-Qing Shen High-Field Terahertz Bulk Photovoltaic Effect in Lithium Niobate ...... 146602 C. Somma, K. Reimann, C. Flytzanis, T. Elsaesser, and M. Woerner Floquet Theory of Electron Waiting Times in Quantum-Coherent Conductors ...... 146801 David Dasenbrook, Christian Flindt, and Markus Büttiker Green’s Functions from Real-Time Bold-Line Monte Carlo Calculations: Spectral Properties of the Nonequilibrium Anderson Impurity Model ...... 146802 Guy Cohen, Emanuel Gull, David R. Reichman, and Andrew J. Millis One-Dimensional Weak Antilocalization Due to the Berry Phase in HgTe Wires ...... 146803 M. Mühlbauer, A. Budewitz, B. Büttner, G. Tkachov, E. M. Hankiewicz, C. Brüne, H. Buhmann, and L. W. Molenkamp

Edge Physics of the Quantum Spin Hall Insulator from a Quantum Dot Excited by Optical Absorption ...... 146804 Romain Vasseur and Joel E. Moore Optical Birefringence and Dichroism of Cuprate Superconductors in the THz Regime ...... 147001 Y. Lubashevsky, LiDong Pan, T. Kirzhner, G. Koren, and N. P. Armitage Superconductivity on the Brink of Spin-Charge Order in a Doped Honeycomb Bilayer ...... 147002 Oskar Vafek, James M. Murray, and Vladimir Cvetkovic Tuning Magnetic Coupling in Sr2IrO4 Thin Films with Epitaxial Strain ...... 147201 A. Lupascu, J. P. Clancy, H. Gretarsson, Zixin Nie, J. Nichols, J. Terzic, G. Cao, S. S. A. Seo, Z. Islam, M. H. Upton, Jungho Kim, D. Casa, T. Gog, A. H. Said, Vamshi M. Katukuri, H. Stoll, L. Hozoi, J. van den Brink, and Young-June Kim Lattice-Site-Specific Spin Dynamics in Double Perovskite Sr2CoOsO6 ...... 147202 Binghai Yan, Avijit Kumar Paul, Sudipta Kanungo, Manfred Reehuis, Andreas Hoser, Daniel M. Többens, Walter Schnelle, Robert C. Williams, Tom Lancaster, Fan Xiao, Johannes S. Möller, Stephen J. Blundell, William Hayes, Claudia Felser, and Martin Jansen Crystals of Bound States in the Magnetization Plateaus of the Shastry-Sutherland Model ...... 147203 Philippe Corboz and Frédéric Mila Antiferromagnetic Domain Wall Motion Induced by Spin Waves ...... 147204 Erlend G. Tveten, Alireza Qaiumzadeh, and Arne Brataas Femtosecond Dynamics of Momentum-Dependent Magnetic Excitations from Resonant Inelastic X-Ray Scattering in CaCu2O3 ...... 147401 Valentina Bisogni, Stefanos Kourtis, Claude Monney, Kejin Zhou, Roberto Kraus, Chinnathambi Sekar, Vladimir Strocov, Bernd Büchner, Jeroen van den Brink, Lucio Braicovich, Thorsten Schmitt, Maria Daghofer, and Jochen Geck Suris Tetrons: Possible Spectroscopic Evidence for Four-Particle Optical Excitations of a Two-Dimensional Electron Gas 147402 A. V. Koudinov, C. Kehl, A. V. Rodina, J. Geurts, D. Wolverson, and G. Karczewski Laser Excitation of Lattice-Driven Anharmonic Magnetization Dynamics in Dielectric FeBO3 ...... 147403 D. Afanasiev, I. Razdolski, K. M. Skibinsky, D. Bolotin, S. V. Yagupov, M. B. Strugatsky, A. Kirilyuk, Th. Rasing, and A. V. Kimel Long-Time Correlation in Non-Markovian Dephasing of an Exciton-Phonon System in InAs Quantum Dots ...... 147404 H. Tahara, Y. Ogawa, F. Minami, K. Akahane, and M. Sasaki Ultrafast Switching of the Electric Polarization and Magnetic Chirality in BiFeO3 by an Electric Field ...... 147601 Satadeep Bhattacharjee, Dovran Rahmedov, Dawei Wang, Jorge Íñiguez, and L. Bellaiche Investigation of Surface Magnetic Noise by Shallow Spins in Diamond ...... 147602 T. Rosskopf, A. Dussaux, K. Ohashi, M. Loretz, R. Schirhagl, H. Watanabe, S. Shikata, K. M. Itoh, and C. L. Degen

Soft Matter, Biological, and Interdisciplinary Physics Triplet Correlations Dominate the Transition from Simple to Tetrahedral Liquids ...... 147801 Murari Singh, Debdas Dhabal, Andrew Huy Nguyen, Valeria Molinero, and Charusita Chakravarty Spontaneous Division and Motility in Active Nematic Droplets ...... 147802 Luca Giomi and Antonio DeSimone High-Velocity Drag Friction in Granular Media near the Jamming Point ...... 148001 Yuka Takehara and Ko Okumura Nonmonotonic Effects of Migration in Subdivided Populations ...... 148101 Pierangelo Lombardo, Andrea Gambassi, and Luca Dall’Asta Emergent Spatial Structures in Flocking Models: A Dynamical System Insight ...... 148102 Jean-Baptiste Caussin, Alexandre Solon, Anton Peshkov, Hugues Chaté, Thierry Dauxois, Julien Tailleur, Vincenzo Vitelli, and Denis Bartolo Range Expansion of Heterogeneous Populations ...... 148103 Matthias Reiter, Steffen Rulands, and Erwin Frey Synchronization and Liquid Crystalline Order in Soft Active Fluids ...... 148104 M. Leoni and T. B. Liverpool

Dynamics of Sheared Ellipses and Circular Disks: Effects of Particle Shape ...... 148301 Somayeh Farhadi and Robert P. Behringer Quantum Simulation of Collective Proton Tunneling in Hexagonal Ice Crystals ...... 148302 Christof Drechsel-Grau and Dominik Marx Adsorption and Pattern Recognition of Polymers at Complex Surfaces with Attractive Stripelike Motifs ...... 148303 Monika Möddel, Wolfhard Janke, and Michael Bachmann Theory and Simulations of Electrocatalyst-Coated Semiconductor Electrodes for Solar Water Splitting ...... 148304 Thomas J. Mills, Fuding Lin, and Shannon W. Boettcher Controlling the Position of Traveling Waves in Reaction-Diffusion Systems ...... 148305 Jakob Löber and Harald Engel Slowing Down of Accelerated Structural Relaxation in Ultrathin Polymer Films ...... 148306 Qiyun Tang, Wenbing Hu, and Simone Napolitano Resonant Acoustic Propagation and Negative Density in Liquid Foams ...... 148307 Juliette Pierre, Benjamin Dollet, and Valentin Leroy Enhanced Flow in Small-World Networks ...... 148701 Cláudio L. N. Oliveira, Pablo A. Morais, André A. Moreira, and José S. Andrade

Errata Publisher’s Note: Self-Assembly of Bicomponent Molecular Monolayers: Adsorption Height Changes and Their Consequences [Phys. Rev. Lett. 112, 117602 (2014)] ...... 149901 E. Goiri, M. Matena, A. El-Sayed, J. Lobo-Checa, P. Borghetti, C. Rogero, B. Detlefs, J. Duvernay, J. E. Ortega, and D. G. de Oteyza Erratum: Standard Model Predictions for B → Klþl− with Form Factors from Lattice QCD [Phys. Rev. Lett. 111, 162002 (2013)] ...... 149902 Chris Bouchard, G. Peter Lepage, Christopher Monahan, Heechang Na, and Junko Shigemitsu (HPQCD Collaboration) Publisher’s Note: Interaction of Relativistic Electron-Vortex Beams with Few-Cycle Laser Pulses [Phys. Rev. Lett. 112, 134801 (2014)] ...... 149903 Armen G. Hayrapetyan, Oliver Matula, Andrea Aiello, Andrey Surzhykov, and Stephan Fritzsche

Selected for a Viewpoint in Physics. Please visit http://physics.aps.org/. By suggesting a few manuscripts each week, we hope to promote reading across fields. Please see our Announcement Phys. Rev. Lett. 98, 010001 (2007).

The American Physical Society’s free online publication, Physics (http://physics.aps.org/), provides thought- provoking analysis and spotlights exceptional research.