Showing papers in "Physical Review X in 2016"
TL;DR: The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers as discussed by the authors.
Abstract: The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper we present full results from a search for binary black hole merger signals with total masses up to 100M⊙ and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than 5σ over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance, which has a 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations we infer stellar-mass binary black hole merger rates lying in the range 9−240Gpc−3yr−1. These observations are beginning to inform astrophysical predictions of binary black hole formation rates, and indicate that future observing runs of the Advanced detector network will yield many more gravitational wave detections.
1,172 citations
TL;DR: In this paper, the first electronic structure calculation performed on a quantum computer without exponentially costly precompilation is reported, where a programmable array of superconducting qubits is used to compute the energy surface of molecular hydrogen using two distinct quantum algorithms.
Abstract: We report the first electronic structure calculation performed on a quantum computer without exponentially costly precompilation. We use a programmable array of superconducting qubits to compute the energy surface of molecular hydrogen using two distinct quantum algorithms. First, we experimentally execute the unitary coupled cluster method using the variational quantum eigensolver. Our efficient implementation predicts the correct dissociation energy to within chemical accuracy of the numerically exact result. Second, we experimentally demonstrate the canonical quantum algorithm for chemistry, which consists of Trotterization and quantum phase estimation. We compare the experimental performance of these approaches to show clear evidence that the variational quantum eigensolver is robust to certain errors. This error tolerance inspires hope that variational quantum simulations of classically intractable molecules may be viable in the near future.
925 citations
TL;DR: In this article, the authors present a framework for studying transport in integrable systems: hydrodynamics with infinitely many conservation laws, and apply it to the description of energy transport between heat baths, and provide a full description of the current-carrying nonequilibrium steady state and the transition regions in a family of models including the Lieb-Liniger model of interacting Bose gases.
Abstract: Understanding the general principles underlying strongly interacting quantum states out of equilibrium is one of the most important tasks of current theoretical physics. With experiments accessing the intricate dynamics of many-body quantum systems, it is paramount to develop powerful methods that encode the emergent physics. Up to now, the strong dichotomy observed between integrable and nonintegrable evolutions made an overarching theory difficult to build, especially for transport phenomena where space-time profiles are drastically different. We present a novel framework for studying transport in integrable systems: hydrodynamics with infinitely many conservation laws. This bridges the conceptual gap between integrable and nonintegrable quantum dynamics, and gives powerful tools for accurate studies of space-time profiles. We apply it to the description of energy transport between heat baths, and provide a full description of the current-carrying nonequilibrium steady state and the transition regions in a family of models including the Lieb-Liniger model of interacting Bose gases, realized in experiments.
562 citations
TL;DR: In this article, a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands is introduced, which synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping.
Abstract: We introduce a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system’s excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and read out schemes as well.
471 citations
TL;DR: Experiments with ultracold magnetic atoms reveal liquid-like quantum droplets that are 20 times larger than previously observed droplets as discussed by the authors, which is the largest known quantum droplet size.
Abstract: Experiments with ultracold magnetic atoms reveal liquid-like quantum droplets that are 20 times larger than previously observed droplets.
448 citations
TL;DR: In this paper, the authors have determined how to accurately and efficiently treat long-range Van der Waals interactions together with other chemical bonds, new findings that are important for studies of layered materials.
Abstract: Van der Waals interactions are ubiquitous in different materials yet not always described properly by current theories. Now, researchers have determined how to accurately and efficiently treat long-range Van der Waals interactions together with other chemical bonds, new findings that are important for studies of layered materials.
426 citations
TL;DR: The authors showed that small changes to single-cell behavior can cause tissue to transition between a fluid-like and a solid-like state, leading to metastatic cell escape from tumors and embryonic development.
Abstract: 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.
354 citations
TL;DR: It is demonstrated how finite range tunneling can provide considerable computational advantage over classical processors for a crafted problem designed to have tall and narrow energy barriers separating local minima, the D-Wave 2X quantum annealer achieves significant runtime advantages relative to Simulated Annealing.
Abstract: 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).
351 citations
TL;DR: In this paper, the authors make a careful study of the use of metasurfaces to transform the impinging optical wave front, and propose a method to enable advanced control of electromagnetic waves over deeply subwavelength thicknesses.
Abstract: Metasurfaces are engineered systems that enable advanced control of electromagnetic waves over deeply subwavelength thicknesses. Researchers make a careful study of the use of metasurfaces to transform the impinging optical wave front.
347 citations
TL;DR: Bosons and fermions, once thought to be distinct entities, can actually be exchanged via the attachment of flux as mentioned in this paper, which is used to relate different theories that have applications in fields as diverse as condensed matter physics and string theory.
Abstract: 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.
330 citations
TL;DR: In this paper, it was shown that it is always possible to estimate the separation of two stars, no matter how close they are, regardless of how distant they are from each other.
Abstract: Quantum metrology shows that it is always possible to estimate the separation of two stars, no matter how close together they are.
TL;DR: In this paper, the physical properties of triple point fermions have been theoretically analyzed, which can be thought of as a melding of Dirac and Weyl Fermions.
Abstract: 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.
TL;DR: In this paper, a study of an ensemble of connected lossy cavities shows how eigenstates can coalesce to produce new higher-order singularities in multiple-state open systems.
Abstract: 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.
TL;DR: In this article, the anomalous Floquet-Anderson insulator (AFAI) is characterized by a quasienergy spectrum featuring chiral edge modes coexisting with a fully localized bulk.
Abstract: We show that two-dimensional periodically driven quantum systems with spatial disorder admit a unique topological phase, which we call the anomalous Floquet-Anderson insulator (AFAI). The AFAI is characterized by a quasienergy spectrum featuring chiral edge modes coexisting with a fully localized bulk. Such a spectrum is impossible for a time-independent, local Hamiltonian. These unique characteristics of the AFAI give rise to a new topologically protected nonequilibrium transport phenomenon: quantized, yet nonadiabatic, charge pumping. We identify the topological invariants that distinguish the AFAI from a trivial, fully localized phase, and show that the two phases are separated by a phase transition.
TL;DR: A new class of quantum error-correcting codes for a bosonic mode which are advantageous for applications in quantum memories, communication, and scalable computation are constructed from a finite superposition of Fock states weighted with binomial coefficients.
Abstract: 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.
TL;DR: In this paper, 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.
Abstract: 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.
TL;DR: In this paper, the electrical double-layer structure of silica-electrolyte interfaces that control capacitance was revealed. But the authors did not reveal the double layer structure of the capacitors themselves.
Abstract: Double-layer capacitors can be used to harness wind and solar energy, and now new measurements reveals the electrical double-layer structure of silica-electrolyte interfaces that controls capacitance.
TL;DR: In this article, a study of topological transport in quasicrystals was conducted and it was shown that a two-dimensional photonic quasICrystal exhibits a topological insulating phase.
Abstract: Quasicrystals are a class of materials that exhibit long-range order but no periodicity. A study of topological transport in quasicrystals shows that, surprisingly, a two-dimensional photonic quasicrystal exhibits a topological insulating phase.
IBM1
TL;DR: In this paper, the tradeoff between employing quantum and classical resources for computational tasks was investigated, and a hybrid quantum-classical computation may be a hallmark of future technologies in future technologies.
Abstract: Hybrid quantum-classical computation may be a hallmark of future technologies. Researchers investigate the tradeoff between employing quantum and classical resources for computational tasks.
TL;DR: In this article, the existence of type-II Weyl semimetals, which would be both conducting and insulating in different spatial directions, has been shown for the first time.
Abstract: Researchers provide new evidence for the existence of type-II Weyl semimetals, which would be both conducting and insulating in different spatial directions.
TL;DR: In this paper, a theoretical examination explores how Dirac and Weyl semimetals respond to both torsional and unidirectional strain, and shows that mechanical strain can mimic the effects of real electromagnetic fields.
Abstract: In certain materials, mechanical strain can mimic the effects of real electromagnetic fields. A theoretical examination explores how Dirac and Weyl semimetals respond to both torsional and unidirectional strain.
TL;DR: In this article, the authors demonstrate tiny trampoline-like mechanical sensors that are exquisitely sensitive to attonewton forces at room temperature and demonstrate that they can measure extremely small forces.
Abstract: 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.
TL;DR: In this paper, a quantum key distribution network spread over a metropolitan area is shown to be secure against untrustworthy relays, where the relays are assumed to be untrusted.
Abstract: Unconditionally secure communication between remote parties has many applications in finance and industry. Now, a quantum key distribution network spread over a metropolitan area is shown to be secure against untrustworthy relays.
TL;DR: In this article, the authors sharpen the theory of coherence by finding links with interferometry and quantum correlations, which is a fundamental feature of quantum theory and promises to underpin many future quantum technologies.
Abstract: Coherence is a fundamental feature of quantum theory and promises to underpin many future quantum technologies. By studying processes where it is not a necessary resource, researchers sharpen the theory of coherence finding links with interferometry and quantum correlations.
TL;DR: The behavior of smooth FPT densities, for which all moments are finite, is explained and universal yet generally non-Poissonian long-time asymptotics for a broad variety of transport processes are demonstrated.
Abstract: Target search processes can be found in a variety of fields spanning animal science, disease spreading, geophysics, and molecular signaling in biology. A theoretical analysis of the distribution of particles arriving at a target a certain distance away from their origin is presented.
TL;DR: In this article, the electron-phonon coupling and the corresponding energy exchange are investigated experimentally and by ab initio theory in nonequilibrium states of the free-electron metal aluminium.
Abstract: The electron-phonon coupling and the corresponding energy exchange are investigated experimentally and by ab initio theory in nonequilibrium states of the free-electron metal aluminium. The temporal evolution of the atomic mean-squared displacement in laser-excited thin freestanding films is monitored by femtosecond electron diffraction. The electron-phonon coupling strength is obtained for a range of electronic and lattice temperatures from density functional theory molecular dynamics simulations. The electron-phonon coupling parameter extracted from the experimental data in the framework of a twotemperature model (TTM) deviates significantly from the ab initio values. We introduce a nonthermal lattice model (NLM) for describing nonthermal phonon distributions as a sum of thermal distributions of the three phonon branches. The contributions of individual phonon branches to the electron-phonon coupling are considered independently and found to be dominated by longitudinal acoustic phonons. Using all material parameters from first-principles calculations except the phonon-phonon coupling strength, the prediction of the energy transfer from electrons to phonons by the NLM is in excellent agreement with time-resolved diffraction data. Our results suggest that the TTM is insufficient for describing the microscopic energy flow even for simple metals like aluminium and that the determination of the electronphonon coupling constant from time-resolved experiments by means of the TTM leads to incorrect values. In contrast, the NLM describing transient phonon populations by three parameters appears to be a sufficient model for quantitatively describing electron-lattice equilibration in aluminium. We discuss the general applicability of the NLM and provide a criterion for the suitability of the two-temperature approximation for other metals.
TL;DR: In this paper, the spin-orbit interactions of electrons directly at the interface between graphene and transition-metal dichalcogenides were studied, leading to intriguing phenomena such as topological insulating states.
Abstract: Spin-orbit interactions are responsible for intriguing phenomena such as topological insulating states. Now, scientists study the spin-orbit interactions of electrons directly at the interface between graphene and transition-metal dichalcogenides.
TL;DR: Using lattice models populated with Dirac electrons, the authors presented a numerically exact investigation of the metal-insulator transition, which is an important aspect of quantum mechanics, and showed that the transition can be computed numerically.
Abstract: The metal-insulator transition is an important aspect of quantum mechanics. Using lattice models populated with Dirac electrons, researchers present a numerically exact investigation of this transition.
TL;DR: This work establishes an infinite family of quantum speed limits valid for unitary and nonunitary evolutions, based on an elegant information geometric formalism, and provides instances of novel bounds which are tighter than any established one based on the conventional quantum Fisher information.
Abstract: The attempt to gain a theoretical understanding of the concept of time in quantum mechanics has triggered significant progress towards the search for faster and more efficient quantum technologies. One of such advances consists in the interpretation of the time-energy uncertainty relations as lower bounds for the minimal evolution time between two distinguishable states of a quantum system, also known as quantum speed limits. We investigate how the nonuniqueness of a bona fide measure of distinguishability defined on the quantum-state space affects the quantum speed limits and can be exploited in order to derive improved bounds. Specifically, we establish an infinite family of quantum speed limits valid for unitary and nonunitary evolutions, based on an elegant information geometric formalism. Our work unifies and generalizes existing results on quantum speed limits and provides instances of novel bounds that are tighter than any established one based on the conventional quantum Fisher information. We illustrate our findings with relevant examples, demonstrating the importance of choosing different information metrics for open system dynamics, as well as clarifying the roles of classical populations versus quantum coherences, in the determination and saturation of the speed limits. Our results can find applications in the optimization and control of quantum technologies such as quantum computation and metrology, and might provide new insights in fundamental investigations of quantum thermodynamics.
TL;DR: 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 as discussed by the authors.
Abstract: 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.