We discuss a scheme to measure the many-body entanglement growth during quench dynamics with bosonic atoms in optical lattices. By making use of a 1D or 2D setup in which two copies of the same state are prepared, we show how arbitrary order Rényi entropies can be extracted by using tunnel coupling between the copies and measurement of the parity of on-site occupation numbers, as has been performed in recent experiments. We illustrate these ideas for a superfluid-Mott insulator quench in the Bose-Hubbard model, and also for hard-core bosons, and show that the scheme is robust against imperfections in the measurements.

The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use $15\mathrm{kg}\mathrm{day}$ of data acquired in 2006 to set limits on the dark-matter—electron scattering cross section. The strongest bound is obtained at 100 MeV where ${\sigma }_e<3\times {10}^{-38}{\mathrm{cm}}^2$ at 90% C.L., while dark-matter masses between 20 MeV and 1 GeV are bounded by ${\sigma }_e<{10}^{-37}{\mathrm{cm}}^2$ at 90% C.L. This analysis provides a first proof of principle that direct detection experiments can be sensitive to dark-matter candidates with masses well below the GeV scale.

The unbound excited states of the neutron drip-line isotope ${}^{24}\mathrm{O}$ have been investigated via the ${}^{24}\mathrm{O}(p,p^{\prime }){}^{23}\mathrm{O}+n$ reaction in inverse kinematics at a beam energy of $62\mathrm{MeV}/\mathrm{nucleon}$. The decay energy spectrum of ${}^{24}\mathrm{O}^{*}$ was reconstructed from the momenta of ${}^{23}\mathrm{O}$ and the neutron. The spin parity of the first excited state, observed at $E_x=4.65\pm 0.14\mathrm{MeV}$, was determined to be $J^{\pi }=2^{+}$ from the angular distribution of the cross section. Higher-lying states were also observed. The quadrupole transition parameter ${\beta }_2$ of the $2_1^{+}$ state was deduced, for the first time, to be $0.15\pm 0.04$. The relatively high excitation energy and small ${\beta }_2$ value are indicative of the $N=16$ shell closure in ${}^{24}\mathrm{O}$.

We investigate both experimentally and theoretically the far-field diffraction patterns of single circular apertures as a function of their diameters $d$ and at a given illumination wavelength $\lambda$. We observe the transition between the well-known pseudoscalar regime of large holes ($d\gg \lambda$) and the less-known vectorial regime of subwavelength ones ($d\ll \lambda$). Four different diffraction regimes are identified for different $d/\lambda$ regions, each one with its polarization dependence. A thorough comparison with a theoretical model, which takes into account both finite hole size and the dielectric properties of the metal, allows us to explain and understand the physical processes leading to this behavior. Our results reveal the subtle interplay between two competing factors, one related to polarization symmetries associated with surface-plasmon excitations and the other originating in the coupling of the field to the waveguide mode of the aperture.

A Bessel beam without an axial gradient can exert a pulling force on an object [A. Novitsky, C. W. Qiu, and H. Wang, Phys. Rev. Lett. 107, 203601 (2011)]. However, it cannot be called a “tractor beam” per se, as long as the light pulling effect is ultrasensitive to the object’s material and size, a perturbation of which will make the optical traction go away. In this Letter, we investigate and report on the universality for a Bessel beam to be either a material-independent or size-independent optical tractor beam within the dipolar regime. Moreover, a general condition for a nonparaxial laser to be simultaneously a material- and size-independent tractor beam is proposed. These universal pulling effects and conditions are discussed in association with insight on modified far-field scattering, scattering resonances, and induced polarizabilities. Interestingly, we find that the acoustic pulling force exhibits only size independence, owing to the acoustic scattering theory in contrast to the light scattering counterpart. The findings pave the way for the realistic engineering and application of universal tractor beams pulling a wide variety of objects.

We provide experimental and numerical evidence of in-blades vortices in the von Kármán swirling flow. We estimate the associated kinematic $\alpha$-effect tensor and show that it is compatible with recent models of the von Kármán sodium (VKS) dynamo. We further show that depending on the relative frequency of the two impellers, the dominant dynamo mechanism may switch from ${\alpha }^2$ to $\alpha -\Omega$ dynamo. We discuss some implications of these results for VKS experiments.

The transition from weak to strong turbulence when passing from large to small scales in magnetohydrodynamic (MHD) turbulence with guide field is a cornerstone of anisotropic turbulence theory. We present the first check of this transition, using the Shell-RMHD, which combines a shell model of perpendicular nonlinear coupling and linear propagation along the guide field. This model allows us to reach Reynolds numbers around ${10}^6$. We obtain surprisingly good agreement with the theoretical predictions, with a reduced perpendicular energy spectrum scaling as $k_{\perp }^{-2}$ at large scales and as $k_{\perp }^{-5/3}$ at small scales, where critical balance between nonlinear and propagation time is reached. However, even in the strong regime, a high level of excitation is found in the weak coupling region of Fourier space, which is due to the rich frequency spectrum of large eddies. A corollary is that the reduced parallel spectral slope is not a definite test of the spectral anisotropy, contrary to standard belief.

SiGe heteroepitaxy on vicinal Si (1 1 10) is studied as a model system for one-dimensional (1D) to three-dimensional growth mode transitions. By in situ scanning tunneling microscopy it is shown that the 1D-3D transition proceeds smoothly from perfectly facetted 1D nanoripples to coarsened superripples, tadpoles, asymmetric domes, and barns without involving coalescence or agglomeration. By extension of the studies to a wide range of SiGe compositions, a 1D-3D growth phase diagram is obtained. Total energy calculations reveal that the observed critical transition volumes are fully consistent with thermodynamic driven strain relaxation.

The pressure-dependent relation between Eu valence and lattice structure in model compound EuO is studied with synchrotron-based x-ray spectroscopic and diffraction techniques. Contrary to expectation, a 7% volume collapse at $\approx 45\mathrm{GPa}$ is accompanied by a reentrant Eu valence transition into a lower valence state. In addition to highlighting the need for probing both structure and electronic states directly when valence information is sought in mixed-valent systems, the results also show that widely used bond-valence methods fail to quantitatively describe the complex electronic valence behavior of EuO under pressure.

Intracellular cargo transport can arise from passive diffusion, active motor-driven transport along cytoskeletal filament networks, and passive advection by fluid flows entrained by such cargo-motor motion. Active and advective transport are thus intrinsically coupled as related, yet different representations of the same underlying network structure. A reaction-advection-diffusion system is used here to show that this coupling affects the transport and localization of a passive tracer in a confined geometry. For sufficiently low diffusion, cargo localization to a target zone is optimized either by low reaction kinetics and decoupling of bound and unbound states, or by a mostly disordered cytoskeletal network with only weak directional bias. These generic results may help to rationalize subtle features of cytoskeletal networks, for example as observed for microtubules in fly oocytes.

We study the contextuality of a three-level quantum system using classical conditional entropy of measurement outcomes. First, we analytically construct the minimal configuration of measurements required to reveal contextuality. Next, an entropic contextual inequality is formulated, analogous to the entropic Bell inequalities derived by Braunstein and Caves [Phys. Rev. Lett. 61, 662 (1988)], that must be satisfied by all noncontextual theories. We find optimal measurements for violation of this inequality. The approach is easily extendable to higher dimensional quantum systems and more measurements. Our theoretical findings can be verified in the laboratory with current technology.

We theoretically demonstrate the possibility of observing the macroscopic Zeno effect for nonlinear waveguides with localized dissipation. We show the existence of stable stationary flows, which are balanced by losses in the dissipative domain. The macroscopic Zeno effect manifests itself in the nonmonotonic dependence of the stationary flow on the strength of the dissipation. In particular, we highlight the importance of the dissipation parameters in observing the phenomenon. Our results are applicable to a large variety of systems, including the condensates of atoms or quasiparticles and optical waveguides.

We demonstrate a simple pulse shaping technique designed to improve the fidelity of spin-dependent force operations commonly used to implement entangling gates in trapped ion systems. This extension of the Mølmer-Sørensen gate can theoretically suppress the effects of certain frequency and timing errors to any desired order and is demonstrated through Walsh modulation of a two qubit entangling gate on trapped atomic ions. The technique is applicable to any system of qubits coupled through collective harmonic oscillator modes.

The asymmetric inclusion process is a lattice-gas model which replaces the “fermionic” exclusion interactions of the asymmetric exclusion process by “bosonic” inclusion interactions. Combining together probabilistic and Monte Carlo analyses, we showcase the model’s rich statistical complexity—which ranges from “mild” to “wild” displays of randomness: Gaussian load and draining, Rayleigh outflow with linear aging, inverse-Gaussian coalescence, intrinsic power-law scalings and power-law fluctuations and condensation.

We observe evidence for $CP$ violation in the decay $D^{+}\to K_S^0{\pi }^{+}$ using a data sample with an integrated luminosity of $977{\mathrm{fb}}^{-1}$ collected by the Belle detector at the KEKB $e^{+}{e}^{-}$ asymmetric-energy collider. The $CP$ asymmetry in the decay is measured to be $(-0.363\pm 0.094\pm 0.067)\%$, which is 3.2 standard deviations away from zero, and is consistent with the expected $CP$ violation due to the neutral kaon in the final state.

We report on crossed-beam experiments and quantum-mechanical calculations performed on the $\mathrm{CO}(j=0)+{\mathrm{H}}_2(j=0)\to \mathrm{CO}(j=1)+{\mathrm{H}}_2(j=0)$ system. The experimental cross sections determined in the threshold region of the $\mathrm{CO}(j=0\to j=1)$ transition at $3.85{\mathrm{cm}}^{-1}$ show resonance structures in good qualitative agreement with the theoretical ones. These results suggest that the potential energy surface which describes the $\mathrm{CO}\mathrm{\text{−}}{\mathrm{H}}_2$ van der Waals interaction should be reinvestigated for good quantitative agreement.

We present a scheme for achieving macroscopic quantum superpositions in optomechanical systems by using single photon postselection and detecting them with nested interferometers. This method relieves many of the challenges associated with previous optical schemes for measuring macroscopic superpositions and only requires the devices to be in the weak coupling regime. It requires only small improvements on currently achievable device parameters and allows the observation of decoherence on a time scale unconstrained by the system’s optical decay time. Prospects for observing novel decoherence mechanisms are discussed.

We demonstrate, through experiment and theory, enhanced high-frequency current oscillations due to magnetically-induced conduction resonances in superlattices. Strong increase in the ac power originates from complex single-electron dynamics, characterized by abrupt resonant transitions between unbound and localized trajectories, which trigger and shape propagating charge domains. Our data demonstrate that external fields can tune the collective behavior of quantum particles by imprinting configurable patterns in the single-particle classical phase space.

We study the properties of spin systems realized by cold polar molecules interacting via dipole-dipole interactions in two dimensions. Using a spin wave theory, that allows for the full treatment of the characteristic long-distance tail of the dipolar interaction, we find several anomalous features in the ground state correlations and the spin wave excitation spectrum, which are absent in their counterparts with short-range interaction. The most striking consequence is the existence of true long-range order at finite temperature for a two-dimensional phase with a broken $U(1)$ symmetry.

We report on the nonlinear coupling between the mechanical modes of a nanotube resonator. The coupling is revealed in a pump-probe experiment where a mode driven by a pump force is shown to modify the motion of a second mode measured with a probe force. In a second series of experiments, we actuate the resonator with only one oscillating force. Mechanical resonances feature exotic line shapes with reproducible dips, peaks, and jumps when the measured mode is commensurate with another mode with a frequency ratio of either 2 or 3. Conventional line shapes are recovered by detuning the frequency ratio using the voltage on a nearby gate electrode. The exotic line shapes are attributed to strong coupling between the mechanical modes. The possibility to control the strength of the coupling with the gate voltage holds promise for various experiments, such as quantum manipulation, mechanical signal processing, and the study of the quantum-to-classical transition.