Weak value measurements have recently given rise to a great amount of interest in both the possibility of measurement amplification and the chance for further quantum mechanics foundations investigation. In particular, a question emerged about weak values being proof of the incompatibility between quantum mechanics and noncontextual hidden variables theories (NCHVTs). A test to provide a conclusive answer to this question was given by Pusey [Phys. Rev. Lett. 113, 200401 (2014)], where a theorem was derived showing the NCHVT incompatibility with the observation of anomalous weak values under specific conditions. In this Letter we realize this proposal, clearly pointing out the connection between weak values and the contextual nature of quantum mechanics.

We propose to increase the fidelity of two-qubit resonator-induced phase gates in circuit QED by the use of narrow-band single-mode squeezing. We show that there exists an optimal squeezing angle and strength that erases qubit “which-path” information leaking out of the cavity and thereby minimizes qubit dephasing during these gates. Our analytical results for the gate fidelity are in excellent agreement with numerical simulations of a cascaded master equation that takes into account the dynamics of the source of squeezed radiation. With realistic parameters, we find that it is possible to realize a controlled-phase gate with a gate time of 200 ns and average infidelity of $10^{-5}$.

We derive the exact mass-coupling relation of the simplest multiscale quantum integrable model, i.e., the homogeneous sine-Gordon model with two mass scales. The relation is obtained by comparing the perturbed conformal field theory description of the model valid at short distances to the large distance bootstrap description based on the model’s integrability. In particular, we find a differential equation for the relation by constructing conserved tensor currents, which satisfy a generalization of the $\mathrm{\Theta }$ sum rule Ward identity. The mass-coupling relation is written in terms of hypergeometric functions.

In this Letter we provide a complete holographic reconstruction of the cubic couplings in the minimal bosonic higher spin theory in ($d+1$)-dimensional anti– de Sitter space. For this purpose, we also determine the operator-product expansion coefficients of all single-trace conserved currents in the $d$-dimensional free scalar $O(N)$ vector model, and we compute the tree-level three-point Witten diagram amplitudes for a generic cubic interaction of higher spin gauge fields in the metriclike formulation.

We observe interference in the light scattered from trapped ${{}^{40}\mathrm{Ca}}^{+}$ ion crystals. By varying the intensity of the excitation laser, we study the influence of elastic and inelastic scattering on the visibility of the fringe pattern and discriminate its effect from that of the ion temperature and wave-packet localization. In this way we determine the complex degree of coherence and the mutual coherence of light fields produced by individual atoms. We obtain interference fringes from crystals consisting of two, three, and four ions in a harmonic trap. Control of the trapping potential allows for the adjustment of the interatomic distances and thus the formation of linear arrays of atoms serving as a regular grating of microscopic scatterers.

We show that the resonance shifts in the fluorescence of a cold gas of rubidium atoms substantially differ from those of thermal atomic ensembles that obey the standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements of the resonance shifts in a steady-state response in light propagation.

A sideband cooling strategy that incorporates (i) the dynamics induced by structured (non-Markovian) environments in the target and auxiliary systems and (ii) the optimally time-modulated interaction between them is developed. For the context of cavity optomechanics, when non-Markovian dynamics are considered in the target system, ground state cooling is reached at much faster rates and at a much lower phonon occupation number than previously reported. In contrast to similar current strategies, ground state cooling is reached here for coupling-strength rates that are experimentally accessible for the state-of-the-art implementations. After the ultrafast optimal-ground-state-cooling protocol is accomplished, an additional optimal control strategy is considered to maintain the phonon number as close as possible to the one obtained in the cooling procedure. Contrary to the conventional expectation, when non-Markovian dynamics are considered in the auxiliary system, the efficiency of the cooling protocol is undermined.

The contact angle of a liquid drop moving on a real solid surface depends on the speed and direction of motion of the three-phase contact line. Many experiments have demonstrated that pinning on surface defects, thermal activation and viscous dissipation impact contact line dynamics, but so far, efforts have failed to disentangle the role of each of these dissipation channels. Here, we propose a unifying multiscale approach that provides a single quantitative framework. We use this approach to successfully account for the dynamics measured in a classic dip-coating experiment performed over an unprecedentedly wide range of velocity. We show that the full contact line dynamics up to the liquid film entrainment threshold can be parametrized by the size, amplitude and density of nanometer-scale defects. This leads us to reinterpret the contact angle hysteresis as a dynamical crossover rather than a depinning transition.

Comprehensive studies of lattice dynamics in the ferromagnetic semiconductor EuO have been performed by a combination of inelastic x-ray scattering, nuclear inelastic scattering, and ab initio calculations. A remarkably large broadening of the transverse acoustic phonons was discovered at temperatures above and below the Curie temperature $T_C=69\mathrm{K}$. This result indicates a surprisingly strong momentum-dependent spin-phonon coupling induced by the spin dynamics in EuO.

We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about $180\mathrm{kV}/\mathrm{cm}$. Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These “strong” ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid $[{\mathrm{P}}_{6,6,6,14}][\mathrm{Cl}]$ points to ion association effects. This “weak” ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models.

Charge carrier localization in extended atomic systems has been described previously as being driven by disorder, point defects, or distortions of the ionic lattice. Here we show for the first time by means of first-principles computations that charge carriers can spontaneously localize due to a purely electronic effect in otherwise perfectly ordered structures. Optimally tuned range-separated density functional theory and many-body perturbation calculations within the $GW$ approximation reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange-induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies, and the optimally tuned range parameter itself all become independent of polymer length as it exceeds the critical localization length. Moreover, we find that lattice disorder and the formation of a polaron result from the charge localization in contrast to the traditional view that lattice distortions precede charge localization. Our results can explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses.

The relatively low magnetocrystalline anisotropy (MCA) in strongly correlated manganites $(\mathrm{La},\mathrm{Sr}){\mathrm{MnO}}_3$ has been a major hurdle for implementing them in spintronic applications. Here we report an unusual, giant enhancement of in-plane MCA in 6 nm ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ (LSMO) films grown on (001) ${\mathrm{SrTiO}}_3$ substrates when the top 2 nm is patterned into periodic stripes of 100 or 200 nm width. Planar Hall effect measurements reveal an emergent uniaxial anisotropy superimposed on one of the original biaxial easy axes for unpatterned LSMO along $⟨110⟩$ directions, with a 50-fold enhanced anisotropy energy density of $5.6\times {10}^6\mathrm{erg}/{\mathrm{cm}}^3$ within the nanostripes, comparable to the value for cobalt. The magnitude and direction of the uniaxial anisotropy exclude shape anisotropy and the step edge effect as its origin. High resolution transmission electron microscopy studies reveal a nonequilibrium strain distribution and drastic suppression in the $c$-axis lattice constant within the nanostructures, which is the driving mechanism for the enhanced uniaxial MCA, as suggested by first-principles density functional calculations.

Randomness is both a useful way to model natural systems and a useful tool for engineered systems, e.g., in computation, communication, and control. Fully random transformations require exponential time for either classical or quantum systems, but in many cases pseudorandom operations can emulate certain properties of truly random ones. Indeed, in the classical realm there is by now a well-developed theory regarding such pseudorandom operations. However, the construction of such objects turns out to be much harder in the quantum case. Here, we show that random quantum unitary time evolutions (“circuits”) are a powerful source of quantum pseudorandomness. This gives for the first time a polynomial-time construction of quantum unitary designs, which can replace fully random operations in most applications, and shows that generic quantum dynamics cannot be distinguished from truly random processes. We discuss applications of our result to quantum information science, cryptography, and understanding the self-equilibration of closed quantum dynamics.

We present a QCD calculation of the $u$, $d$, and $s$ scalar quark contents of nucleons based on 47 lattice ensembles with $N_f=2+1$ dynamical sea quarks, 5 lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and pion masses down to 120 MeV. Using the Feynman-Hellmann theorem, we obtain $f_{ud}^N=0.0405(40)(35)$ and $f_s^N=0.113(45)(40)$, which translates into ${\sigma }_{\pi N}=38(3)(3)\mathrm{MeV}$, ${\sigma }_{sN}=105(41)(37)\mathrm{MeV}$, and $y_N=0.20(8)(8)$ for the sigma terms and the related ratio, where the first errors are statistical and the second errors are systematic. Using isospin relations, we also compute the individual up and down quark contents of the proton and neutron (results in the main text).

Precision measurements of superallowed Fermi $\beta$-decay transitions, particularly for the lightest superallowed emitters ${}^{10}\mathrm{C}$ and ${}^{14}\mathrm{O}$, set stringent limits on possible scalar current contributions to the weak interaction. In the present work, a discrepancy between recent measurements of the ${}^{10}\mathrm{C}$ half-life is addressed through two high-precision half-life measurements, via $\gamma$-ray photopeak and $\beta$ counting, that yield consistent results for the ${}^{10}\mathrm{C}$ half-life of $T_{1/2}=19.2969\pm 0.0074\mathrm{s}$ and $T_{1/2}=19.3009\pm 0.0017\mathrm{s}$, respectively. The latter is the most precise superallowed $\beta$-decay half-life measurement reported to date and the first to achieve a relative precision below ${10}^{-4}$. A fit to the world superallowed $\beta$-decay data including the ${}^{10}\mathrm{C}$ half-life measurements reported here yields $b_F=-0.0018\pm 0.0021$ (68% C.L.) for the Fierz interference term and $C_S/C_V=+0.0009\pm 0.0011$ for the ratio of the weak scalar to vector couplings assuming left-handed neutrinos.

We present an experiment using a sample of laser-cooled Rb atoms to show that cross-phase modulation schemes continue to benefit from electromagnetically induced transparency (EIT) even as the transparency window is made narrower than the signal bandwidth (i.e., for signal pulses much shorter than the response time of the EIT system). Addressing concerns that narrow EIT windows might not prove useful for such applications, we show that while the peak phase shift saturates in this regime, it does not drop, and the time-integrated effect continues to scale inversely with EIT window width. This integrated phase shift is an important figure of merit for tasks such as the detection of single-photon-induced cross-phase shifts. Only when the window width approaches the system’s dephasing rate $\gamma$ does the peak phase shift begin to decrease, leading to an integrated phase shift that peaks when the window width is equal to $4\gamma$.

Dispersive shock waves and solitons are fundamental nonlinear excitations in dispersive media, but dispersive shock wave studies to date have been severely constrained. Here, we report on a novel dispersive hydrodynamic test bed: the effectively frictionless dynamics of interfacial waves between two high viscosity contrast, miscible, low Reynolds number Stokes fluids. This scenario is realized by injecting from below a lighter, viscous fluid into a column filled with high viscosity fluid. The injected fluid forms a deformable pipe whose diameter is proportional to the injection rate, enabling precise control over the generation of symmetric interfacial waves. Buoyancy drives nonlinear interfacial self-steepening, while normal stresses give rise to the dispersion of interfacial waves. Extremely slow mass diffusion and mass conservation imply that the interfacial waves are effectively dissipationless. This enables high fidelity observations of large amplitude dispersive shock waves in this spatially extended system, found to agree quantitatively with a nonlinear wave averaging theory. Furthermore, several highly coherent phenomena are investigated including dispersive shock wave backflow, the refraction or absorption of solitons by dispersive shock waves, and the multiphase merging of two dispersive shock waves. The complex, coherent, nonlinear mixing of dispersive shock waves and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.