We present a general theory of non-Markovian dynamics for open systems of noninteracting fermions (bosons) linearly coupled to thermal environments of noninteracting fermions (bosons). We explore the non-Markovian dynamics by connecting the exact master equations with the nonequilibirum Green’s functions. Environmental backactions are fully taken into account. The non-Markovian dynamics consists of nonexponential decays and dissipationless oscillations. Nonexponential decays are induced by the discontinuity in the imaginary part of the self-energy corrections. Dissipationless oscillations arise from band gaps or the finite band structure of spectral densities. The exact analytic solutions for various non-Markovian thermal environments show that non-Markovian dynamics can be largely understood from the environmental-modified spectra of open systems.

We study nonequilibrium phase transitions in the presence of disorder that locally breaks the symmetry between two equivalent macroscopic states. In low-dimensional equilibrium systems, such random-field disorder is known to have dramatic effects: it prevents spontaneous symmetry breaking and completely destroys the phase transition. In contrast, we show that the phase transition of the one-dimensional generalized contact process persists in the presence of random-field disorder. The ultraslow dynamics in the symmetry-broken phase is described by a Sinai walk of the domain walls between two different absorbing states. We discuss the generality and limitations of our theory, and we illustrate our results by large-scale Monte Carlo simulations.

We apply a new nonparametric Bayesian method for reconstructing the evolution history of the equation of state $w$ of dark energy, based on applying a correlated prior for $w(z)$, to a collection of cosmological data. We combine the latest supernova (SNLS 3 year or Union 2.1), cosmic microwave background, redshift space distortion, and the baryonic acoustic oscillation measurements (including BOSS, WiggleZ, and 6dF) and find that the cosmological constant appears consistent with current data, but that a dynamical dark energy model which evolves from $w<-1$ at $z\sim 0.25$ to $w>-1$ at higher redshift is mildly favored. Estimates of the Bayesian evidence show little preference between the cosmological constant model and the dynamical model for a range of correlated prior choices. Looking towards future data, we find that the best fit models for current data could be well distinguished from the $\Lambda \mathrm{CDM}$ model by observations such as Planck and Euclid-like surveys.

A search for physics beyond the standard model is performed in events with at least three jets and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=7\mathrm{TeV}$. No significant excess of events above the expected backgrounds is observed in $4.98{\mathrm{fb}}^{-1}$ of data collected with the CMS detector at the Large Hadron Collider. The results are presented in the context of the constrained minimal supersymmetric extension of the standard model and more generically for simplified models. For the simplified models of gluino-gluino and squark-squark production, gluino masses below 1.0 TeV and squark masses below 0.76 TeV are excluded in case the lightest supersymmetric particle mass is below 200 GeV. These results significantly extend previous searches.

Using $pp$ collision data corresponding to $1.0{\mathrm{fb}}^{-1}$ integrated luminosity collected by the LHCb detector, two narrow states are observed in the ${\mathit{\Lambda }}_b^0{\pi }^{+}{\pi }^{-}$ spectrum with masses $5911.97\pm 0.12(\mathrm{stat})\pm 0.02(\mathrm{syst})\pm 0.66({\mathit{\Lambda }}_b^0\mathrm{mass})\mathrm{MeV}/c^2$ and $5919.77\pm 0.08(\mathrm{stat})\pm 0.02(\mathrm{syst})\pm 0.66({\mathit{\Lambda }}_b^0\mathrm{mass})\mathrm{MeV}/c^2$. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited ${\mathit{\Lambda }}_b^0$ baryons, ${\mathit{\Lambda }}_b^{*0}(5912)$ and ${\mathit{\Lambda }}_b^{*0}(5920)$.

We report the experimental demonstration of two quantum networking protocols, namely quantum $1\to 3$ telecloning and open-destination teleportation, implemented using a four-qubit register whose state is encoded in a high-quality two-photon hyperentangled Dicke state. The state resource is characterized using criteria based on multipartite entanglement witnesses. We explore the characteristic entanglement-sharing structure of a Dicke state by implementing high-fidelity projections of the four-qubit resource onto lower-dimensional states. Our work demonstrates for the first time the usefulness of Dicke states for quantum information processing.

We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot’s resonant frequency $f_0$. Two distinct jumping modes emerge: a simple jump, which is optimal above $f_0$, is achievable with a squat maneuver, and a peculiar stutter jump, which is optimal below $f_0$, is generated with a countermovement. A simple dynamical model reveals how optimal lift-off results from nonresonant transient dynamics.

Weak electron-phonon coupling in Au and Cu produces a significant thermal resistance when heat flows from a thin Pt layer into a thin Au or Cu layer on picosecond time scales. Metal bilayers ($\mathrm{Pt}/\mathrm{Au}$ and $\mathrm{Pt}/\mathrm{Cu}$) were prepared by magnetron sputter deposition; thermal transport in the bilayers was studied by time domain thermoreflectance in the temperature range $38<T<300\mathrm{K}$. Analysis of heat transfer in the bilayer yields the electron-phonon coupling parameter $g(T)$ of Au and Cu. Our results for $g(T)$ are consistent with the temperature dependence predicted by the two-temperature model of Kaganov et al. [Sov. Phys. JETP 4, 173 (1957)] and help bridge the gap between data obtained using pump-probe spectroscopy at room temperature and electrical measurements at low temperatures.

We propose a model for the intrinsic quantum criticality of $\beta \mathrm{\text{−}}{\mathrm{YbAlB}}_4$, in which a vortex in momentum space gives rise to a new type of Fermi surface singularity. The unquenched angular momentum of the $|J=7/2,m_J=\pm 5/2⟩$ Yb $4f$ states generates a momentum-space line defect in the hybridization between $4f$ and conduction electrons, leading to a quasi-two-dimensional Fermi surface with a $k_{\perp }^4$ dispersion and a singular density of states proportional to $E^{-1/2}$. We discuss the implications of this line node in momentum space for our current understanding of quantum criticality and its interplay with topology.

$\beta \mathrm{\text{−}}{\mathrm{YbAlB}}_4$ is the unique heavy fermion superconductor that exhibits unconventional quantum criticality without tuning in a strongly intermediate valence state. Despite the large coherence temperature, set by the peak of the longitudinal resistivity, our Hall effect measurements reveal that resonant skew scattering from incoherent local moments persists down to at least $\sim 40\mathrm{K}$, where the Hall coefficient exhibits a distinct minimum signaling another formation of coherence. The observation strongly suggests that the hybridization between $f$ moments and conduction electrons has a two-component character with distinct Kondo or coherence scales $T_K$ of $\sim 40\mathrm{K}$ and 200 K; this is confirmed by the magnetic field dependence of ${\rho }_{xy}$.

Tail states in organic semiconductors have a significant influence on device performances by acting as traps in charge transport. We present a study of the controlled passivation of acceptor tail states in fullerene ${\mathrm{C}}_{60}$ by the addition of electrons introduced by molecular $n$ doping. Using ultralow doping, we are able to successively fill the traps with charges and examine the changes in conductivity, activation energy, mobility, and Fermi-level position. Passivation of the traps leads to an increase of the electron mobility in ${\mathrm{C}}_{60}$ by more than 3 orders of magnitude, to reach $0.21{\mathrm{cm}}^2/(\mathrm{V}\mathrm{s})$.

By means of nuclear spin-lattice relaxation rate $T_1^{-1}$, we follow the spin dynamics as a function of the applied magnetic field in two gapped quasi-one-dimensional quantum antiferromagnets: the anisotropic spin-chain system ${\mathrm{NiCl}}_2\mathrm{\text{−}}4\mathrm{SC}({\mathrm{NH}}_2{)}_2$ and the spin-ladder system $({\mathrm{C}}_5{\mathrm{H}}_{12}\mathrm{N}{)}_2\mathrm{Cu}{\mathrm{Br}}_4$. In both systems, spin excitations are confirmed to evolve from magnons in the gapped state to spinons in the gapless Tomonaga-Luttinger-liquid state. In between, $T_1^{-1}$ exhibits a pronounced, continuous variation, which is shown to scale in accordance with quantum criticality. We extract the critical exponent for $T_1^{-1}$, compare it to the theory, and show that this behavior is identical in both studied systems, thus demonstrating the universality of quantum-critical behavior.

One of the most striking aspects of the 11-year sunspot cycle is that there have been times in the past when some cycles went missing, a most well-known example of this being the Maunder minimum during 1645–1715. Analyses of cosmogenic isotopes (${}^{14}\mathrm{C}$ and ${}^{10}\mathrm{Be}$) indicated that there were about 27 grand minima in the last 11 000 yrs, implying that about $2.7\%$ of the solar cycles had conditions appropriate for forcing the Sun into grand minima. We address the question of how grand minima are produced and specifically calculate the frequency of occurrence of grand minima from a theoretical dynamo model. We assume that fluctuations in the poloidal field generation mechanism and in the meridional circulation produce irregularities of sunspot cycles. Taking these fluctuations to be Gaussian and estimating the values of important parameters from the data of the last 28 solar cycles, we show from our flux transport dynamo model that about $1–4\%$ of the sunspot cycles may have conditions suitable for inducing grand minima.

We provide a characterization of tunneling between coupled topological insulators in 2D and 3D under the influence of a ferromagnetic layer. We explore conditions for such systems to exhibit integer quantum Hall physics and localized fractional charge, also taking into account interaction effects for the 2D case. We show that the effects of tunneling are topologically equivalent to a certain deformation or folding of the sample geometry. Our key advance is the realization that the quantum Hall or fractional charge physics can appear in the presence of only a single magnet unlike previous proposals which involve magnetic domain walls on the surface or edges of topological insulators, respectively. We give illustrative topological folding arguments to prove our results and show that for the 2D case our results are robust even in the presence of interactions.

We study quantum states produced by optimal phase covariant quantum cloners. We argue that cloned quantum superpositions are not macroscopic superpositions in the spirit of Schrödinger’s cat, despite their large particle number. This is indicated by calculating several measures for macroscopic superpositions from the literature, as well as by investigating the distinguishability of the two superposed cloned states. The latter rapidly diminishes when considering imperfect detectors or noisy states and does not increase with the system size. In contrast, we find that cloned quantum states themselves are macroscopic, in the sense of both proposed measures and their usefulness in quantum metrology with an optimal scaling in system size. We investigate the applicability of cloned states for parameter estimation in the presence of different kinds of noise.

Quantum computation that combines the coherence stabilization virtues of decoherence-free subspaces and the fault tolerance of geometric holonomic control is of great practical importance. Some schemes of adiabatic holonomic quantum computation in decoherence-free subspaces have been proposed in the past few years. However, nonadiabatic holonomic quantum computation in decoherence-free subspaces, which avoids a long run-time requirement but with all the robust advantages, remains an open problem. Here, we demonstrate how to realize nonadiabatic holonomic quantum computation in decoherence-free subspaces. By using only three neighboring physical qubits undergoing collective dephasing to encode one logical qubit, we realize a universal set of quantum gates.

The stochastic gravitational-wave background (SGWB) is expected to arise from the superposition of many independent and unresolved gravitational-wave signals of either cosmological or astrophysical origin. The spectral content of the SGWB carries signatures of the physics that generated it. We present a Bayesian framework for estimating the parameters associated with different SGWB models using data from gravitational-wave detectors. We apply this technique to recent results from LIGO to produce the first simultaneous 95% confidence level limits on multiple parameters in generic power-law SGWB models and in SGWB models of compact binary coalescences. We also estimate the sensitivity of the upcoming second-generation detectors such as Advanced LIGO or Virgo to these models and demonstrate how SGWB measurements can be combined and compared with observations of individual compact binary coalescences in order to build confidence in the origin of an observed SGWB signal. In doing so, we demonstrate a novel means of differentiating between different sources of the SGWB.

We report a measurement of the bottom-strange meson mixing phase ${\beta }_s$ using the time evolution of $B_s^0\to J/\psi (\to {\mu }^{+}{\mu }^{-})\varphi (\to K^{+}{K}^{-})$ decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to $9.6{\mathrm{fb}}^{-1}$ of integrated luminosity. We report confidence regions in the two-dimensional space of ${\beta }_s$ and the $B_s^0$ decay-width difference $\Delta {\Gamma }_s$ and measure ${\beta }_s\in [-\pi /2,-1.51]\cup [-0.06,0.30]\cup [1.26,\pi /2]$ at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of ${\beta }_s$, we also determine $\Delta {\Gamma }_s=0.068\pm 0.026(\mathrm{stat})\pm 0.009(\mathrm{syst}){\mathrm{ps}}^{-1}$ and the mean $B_s^0$ lifetime ${\tau }_s=1.528\pm 0.019(\mathrm{stat})\pm 0.009(\mathrm{syst})\mathrm{ps}$, which are consistent and competitive with determinations by other experiments.

The two-photon transition $\psi (3686)\to \gamma \gamma J/\psi$ is studied in a sample of $1.06\times {10}^8$ $\psi (3686)$ decays collected by the BESIII detector. The branching fraction is measured to be $\mathbf{(}3.1\pm 0.6(\mathrm{stat}{)}_{-1.0}^{+0.8}(\mathrm{syst})\mathbf{)}\times {10}^{-4}$ using $J/\psi \to e^{+}{e}^{-}$ and $J/\psi \to {\mu }^{+}{\mu }^{-}$ decays, and its upper limit is estimated to be $4.5\times {10}^{-4}$ at the $90\%$ confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the $\psi (3686)$ decay plane and the $J/\psi$ polarization in this decay are also studied. In addition, the product branching fractions of sequential $E1$ transitions $\psi (3686)\to \gamma {\chi }_{cJ}$ and ${\chi }_{cJ}\to \gamma J/\psi (J=0,1,2)$ are reported.

Recent calculations suggest that the rate of neutron capture by ${}^{130}\mathrm{Sn}$ has a significant impact on late-time nucleosynthesis in the $r$ process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the $N=82$ closed shell, so $r$-process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the ($d$,$p$) reaction has been studied in inverse kinematics using a 630 MeV beam of ${}^{130}\mathrm{Sn}$ ($4.8\mathrm{MeV}/\mathrm{u}$) and a $({\mathrm{CD}}_2{)}_n$ target. An array of Si strip detectors, including the Silicon Detector Array and an early implementation of the Oak Ridge Rutgers University Barrel Array, was used to detect reaction products. Results for the ${}^{130}\mathrm{Sn}(d,\text{}p){}^{131}\mathrm{Sn}$ reaction are found to be very similar to those from the previously reported ${}^{132}\mathrm{Sn}(d,\text{}p){}^{133}\mathrm{Sn}$ reaction. Direct-semidirect ($n$,$\gamma$) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates.