CreatorsPublishersAdvertisers

#The Creative Commons

skeptophilia.com

Skeptophilia

I had a very peculiar thing happen to me while working on my work-in-progress, a fall-of-civilization novel called In the Midst of Lions that I swear was not inspired in any way by 2020. (In fact -- true story -- I first came up with the idea for this book when I was in college. Which was a lot of years ago.)
BOOKS & LITERATURE
Picture for Skeptophilia
APS physics

Characterization of control in a superconducting qutrit using randomized benchmarking

We characterize control of a qutrit implemented in the lowest three energy levels of a capacitively shunted flux-biased superconducting circuit. Randomized benchmarking over the qutrit Clifford group yields an average fidelity of. 98.89. ±. 0.05. %. . For a selected subset of the Clifford group, we perform quantum process tomography...
SCIENCE
APS physics

Universal Limitations on Quantum Key Distribution over a Network

We consider the distribution of secret keys, both in a bipartite and a multipartite (conference) setting, via a quantum network and establish a framework to obtain bounds on the achievable rates. We show that any multipartite private state—the output of a protocol distilling secret key among the trusted parties—has to be genuinely multipartite entangled. In order to describe general network settings, we introduce a multiplex quantum channel, which links an arbitrary number of parties where each party can take the role of sender only, receiver only, or both sender and receiver. We define asymptotic and nonasymptotic local quantum operations and classical communication-assisted secret-key-agreement (SKA) capacities for multiplex quantum channels and provide strong and weak converse bounds. The structure of the protocols we consider, manifested by an adaptive strategy of secret-key and entanglement [Greenberger–Horne–Zeilinger (GHZ) state] distillation over an arbitrary multiplex quantum channel, is generic. As a result, our approach also allows us to study the performance of quantum key repeaters and measurement-device-independent quantum key distribution (MDI-QKD) setups. For teleportation-covariant multiplex quantum channels, we get upper bounds on the SKA capacities in terms of the entanglement measures of their Choi states. We also obtain bounds on the rates at which secret key and GHZ states can be distilled from a finite number of copies of an arbitrary multipartite quantum state. We are able to determine the capacities for MDI-QKD setups and rates of GHZ-state distillation for some cases of interest.
COMPUTERS
TRENDING TOPICS
APS physics

Fast Simulation of Bosonic Qubits via Gaussian Functions in Phase Space

Bosonic qubits are a promising route to building fault-tolerant quantum computers on a variety of physical platforms. Studying the performance of bosonic qubits under realistic gates and measurements is challenging with existing analytical and numerical tools. We present a novel formalism for simulating classes of states that can be represented as linear combinations of Gaussian functions in phase space. This formalism allows us to analyze and simulate a wide class of non-Gaussian states, transformations, and measurements. We demonstrate how useful classes of bosonic qubits—Gottesman-Kitaev-Preskill (GKP), cat, and Fock states—can be simulated using this formalism, opening the door to investigating the behavior of bosonic qubits under Gaussian channels and measurements, non-Gaussian transformations such as those achieved via gate teleportation, and important non-Gaussian measurements such as threshold and photon-number detection. Our formalism enables simulating these situations with levels of accuracy that are not feasible with existing methods. Finally, we use a method informed by our formalism to simulate circuits critical to the study of fault-tolerant quantum computing with bosonic qubits but beyond the reach of existing techniques. Specifically, we examine how finite-energy GKP states transform under realistic qubit phase gates; interface with a continuous-variable cluster state; and transform under non-Clifford t gate teleportation using magic states. We implement our simulation method as a part of the open-source Strawberry Fields python library.
COMPUTERS
APS physics

Emergence of a Sharp Quantum Collective Mode in a One-Dimensional Fermi Polaron

The Fermi-polaron problem of a mobile impurity interacting with fermionic medium emerges in various contexts, ranging from the foundations of Landau’s Fermi-liquid theory to electron-exciton interaction in semiconductors, to unusual properties of high-temperature superconductors. While classically the medium provides only a dissipative environment to the impurity, the quantum picture of polaronic dressing is more intricate and arises from the interplay of few- and many-body aspects of the problem. The conventional expectation for the dynamics of Fermi polarons is that it is dissipative in character, and any excess energy is rapidly emitted away from the impurity as particle-hole excitations. Here we report a strikingly different type of polaron dynamics in a one-dimensional system of the impurity interacting repulsively with the fermions. When the total momentum of the system equals the Fermi momentum, there emerges a sharp collective mode corresponding to long-lived oscillations of the polaronic cloud surrounding the impurity. This mode can be observed experimentally with ultracold atoms using Ramsey interferometry and radio-frequency spectroscopy.
PHYSICS
APS physics

Gravity interpretation for the Bethe Ansatz expansion of the N=4 SYM index

The superconformal index of the N = 4 S U ( N ) supersymmetric Yang-Mills theory counts the. -BPS (Bogomol’nyi-Prasad-Sommerfield) states in this theory, and has been used via the. AdS. /. CFT. correspondence to count black hole microstates of. 1. /. 16. -BPS black holes. On one hand, this...
SCIENCE
Nature.com

Publisher Correction: Effect of small heat release and viscosity on thermal-diffusive instability

Correction to: Scientific Reports https://doi.org/10.1038/s41598-021-99163-6, published online 12 October 2021. The original version of this Article contained errors in Equations 24"“26. In Equation 24, "\(\left[ M \right]\)" was omitted from the HTML version. In Equation 25, "\(\left[ {{\varvec{n}} \times \left( {\varvec{V } \times {\varvec{n}}} \right)} \right]\)" was omitted from the...
SCIENCE
APS physics

Collision of dynamic jamming fronts in a dense suspension

Dynamic jamming is a phenomenon whereby a dense suspension switches from a fluidlike to a solidlike state when subjected to sufficient stress and deformation. Large enough systems show that this transition is accompanied by a distinct jamming front. We present an experimental study where two jamming fronts are created simultaneously using two cylinders moving in parallel. We focus our observations on the collision of the jammed regions when the two fronts meet. Surprisingly, our measurements, combining surface texture visualization and time-resolved particle image velocimetry, show the formation of an unjammed region contained within the otherwise jammed suspension.
SCIENCE
APS physics

Opportunities for Long-Range Magnon-Mediated Entanglement of Spin Qubits via On- and Off-Resonant Coupling

The ability to manipulate entanglement between multiple spatially separated qubits is essential for quantum-information processing. Although nitrogen-vacancy (NV) centers in diamond provide a promising qubit platform, developing scalable two-qubit gates remains a well-known challenge. To this end, magnon-mediated entanglement proposals have attracted attention due to their long-range spin-coherent propagation. Optimal device geometries and gate protocols of such schemes, however, have yet to be determined. Here we predict strong long-distance (
SCIENCE
Nature.com

Author Correction: In situ ultrastructures of two evolutionarily distant apicomplexan rhoptry secretion systems

Correction to: Nature Communications https://doi.org/10.1038/s41467-021-25309-9, published online 17 August 2021. Supplementary Movies 1"“5 and Description of Additional Supplementary Files were missing from this article and have now been uploaded. The original article has been corrected. Author information. Author notes. These authors contributed equally: Amandine Guérin, Liam M. Theveny, William David...
SCIENCE
APS physics

Calibration of Flux Crosstalk in Large-Scale Flux-Tunable Superconducting Quantum Circuits

Magnetic flux tunability is an essential feature in most approaches to quantum computing based on superconducting qubits. Independent control of the fluxes in multiple loops is hampered by crosstalk. Calibrating flux crosstalk becomes a challenging task when the circuit elements interact strongly. We present a novel approach to flux crosstalk calibration, which is circuit model independent and relies on an iterative process to gradually improve calibration accuracy. This method allows us to reduce errors due to the inductive coupling between loops. The calibration procedure is automated and implemented on devices consisting of tunable flux qubits and couplers with up to 27 control loops. We devise a method to characterize the calibration error, which is used to show that the errors of the measured crosstalk coefficients are all below 0.17%.
SCIENCE
APS physics

Experimental Evidence for an Attractive p−ϕ Interaction

This Letter presents the first experimental evidence of the attractive strong interaction between a proton and a. meson. The result is obtained from two-particle correlations of combined. p. −. ϕ. ⊕.  . p. ¯. −. ϕ. pairs measured in high-multiplicity. p. p. collisions at. s. =. 13.  .  . TeV.
SCIENCE
Nature.com

Author Correction: Genetic analysis by targeted next-generation sequencing and novel variation identification of maple syrup urine disease in Chinese Han population

Correction to: Scientific Reports https://doi.org/10.1038/s41598-021-98357-2, published online 23 September 2021. The original version of this Article contained an error in the order of the author names, which was incorrectly given as Xiaohua Fang, Xiaofan Zhu, Yin Feng, Ying Bai, Xuechao Zhao, Xiangdong Kong & Ning Liu. The original Article has...
SCIENCE
Nature.com

Correction: Circulating levels of soluble Dipeptidylpeptidase-4 are reduced in human subjects hospitalized for severe COVID-19 infections

International Journal of Obesity (2021)Cite this article. Correction to: International Journal of Obesity https://doi.org/10.1038/s41366-020-00689-y, published online 21 September 2020. The article Circulating levels of soluble Dipeptidylpeptidase-4 are reduced in human subjects hospitalized for severe COVID-19 infections, written by Kristina Schlicht, Nathalie Rohmann, Corinna Geisler, Tim Hollstein, Carina Knappe, Katharina Hartmann,...
PUBLIC HEALTH
APS physics

Thermodynamics of Statistical Anyons

In low-dimensional systems, indistinguishable particles can display statistics that interpolate between bosons and fermions. Signatures of these “anyons” have been detected in two-dimensional quasiparticle excitations of the fractional quantum Hall effect, however experimental access to these quasiparticles remains limited. As an alternative to these “topological anyons,” we propose “statistical anyons” realized through a statistical mixture of particles with bosonic and fermionic symmetry. We show that the framework of statistical anyons is equivalent to the generalized exclusion statistics (GES) pioneered by Haldane, significantly broadening the range of systems to which GES apply. We develop the full thermodynamic characterizations of these statistical anyons, including both equilibrium and nonequilibrium behavior. To develop a complete picture, we compare the performance of quantum heat engines with working mediums of statistical anyons and traditional topological anyons, demonstrating the effects of the anyonic phase in both local equilibrium and fully nonequilibrium regimes. In addition, methods of optimizing engine performance through shortcuts to adiabaticity are investigated, using both linear response and fast-forward techniques.
PHYSICS
Nature.com

Publisher Correction: Neural attentional-filter mechanisms of listening success in middle-aged and older individuals

Correction to: Nature Communications https://doi.org/10.1038/s41467-021-24771-9, published online 26 July 2021. In the original version of this Article, Fig. 2 was inadvertently omitted in the PDF version of the Article. This has now been corrected in the PDF version of the Article. Author information. Author notes. Lorenz Fiedler. Present address: Eriksholm...
MENTAL HEALTH
APS physics

Mott Insulating States with Competing Orders in the Triangular Lattice Hubbard Model

The physics of the triangular lattice Hubbard model exhibits a rich phenomenology, ranging from a metal-insulator transition, intriguing thermodynamic behavior, and a putative spin liquid phase at intermediate coupling, ultimately becoming a magnetic insulator at strong coupling. In this multimethod study, we combine a finite-temperature tensor network method, minimally entangled thermal typical states (METTS), with two Green-function-based methods, connected-determinant diagrammatic Monte Carlo and cellular dynamical mean-field theory, to establish several aspects of this model. We elucidate the evolution from the metallic to the insulating regime from the complementary perspectives brought by these different methods. We compute the full thermodynamics of the model on a width-four cylinder using METTS in the intermediate to strong coupling regime. We find that the insulating state hosts a large entropy at intermediate temperatures, which increases with the strength of the coupling. Correspondingly, and consistently with a thermodynamic Maxwell relation, the double occupancy has a minimum as a function of temperature which is the manifestation of the Pomeranchuk effect of increased localization upon heating. The intermediate coupling regime is found to exhibit both pronounced chiral as well as stripy antiferromagnetic spin correlations. We propose a scenario in which time-reversal symmetry-broken states compete with stripy-spin states at lowest temperatures.
SCIENCE
APS physics

Ultrafast Vibrational Relaxation Dynamics in XUV-Excited Polycyclic Aromatic Hydrocarbon Molecules

Unraveling ultrafast molecular processes initiated by energetic radiation provides direct information on the chemical evolution under extreme conditions. A prominent example is interstellar media where complex molecules such as polycyclic aromatic hydrocarbons (PAHs) are excited by energetic photons. Until recently, ultrafast dynamics following such excitations remained largely unexplored due to the lack of relevant technologies. Here, we use time-resolved mass spectrometry combining ultrashort femtosecond XUV and IR pulses, to investigate the dynamics induced by high-energy photon excitation in PAHs. We demonstrate that excited cations relax through a progressive loss of vibrational selectivity, created at the early-stage dynamics, and which represents the first steps of a complete intramolecular vibrational energy redistribution. This process is in competition with the recently revealed correlation-band dynamics. These results might have direct consequences for the development of XUV molecular physics and other fields such as astrochemistry.
CHEMISTRY
YOU MAY ALSO LIKE