Quantum mechanics predicts that measurements of incompatible observables carry a minimum uncertainty which is independent of technical deficiencies of the measurement apparatus or incomplete knowledge of the state of the system. Nothing yet seems to prevent a single physical quantity, such as one spin component, from being measured with arbitrary precision. Here, we show that an intrinsic quantum uncertainty on a single observable is ineludible in a number of physical situations. When revealed on local observables of a bipartite system, such uncertainty defines an entire class of bona fide measures of nonclassical correlations. For the case of $2\times d$ systems, we find that a unique measure is defined, which we evaluate in closed form. We then discuss the role that these correlations, which are of the “discord” type, can play in the context of quantum metrology. We show in particular that the amount of discord present in a bipartite mixed probe state guarantees a minimum precision, as quantified by the quantum Fisher information, in the optimal phase estimation protocol.

A general framework is proposed to tackle analytically local quantum quenches in integrable impurity systems, combining a mapping onto a boundary problem with the form factor approach to boundary-condition-changing operators introduced by Lesage and Saleur [Phys. Rev. Lett. 80, 4370 (1998)]. We discuss how to compute exactly the following two central quantities of interest: the Loschmidt echo and the distribution of the work done during the quantum quench. Our results display an interesting crossover physics characterized by the energy scale $T_b$ of the impurity corresponding to the Kondo temperature. We discuss in detail the noninteracting case as a paradigm and benchmark for more complicated integrable impurity models and check our results using numerical methods.

We present an efficient and general method to compute vortex-pinning interactions—which arise in neutron stars, superconductors, and trapped cold atoms—at arbitrary separations using real-time dynamics. This method overcomes uncertainties associated with matter redistribution by the vortex position and the related choice of ensemble that plague the typical approach of comparing energy differences between stationary pinned and unpinned configurations: uncertainties that prevent agreement in the literature on the sign and magnitude of the vortex-nucleus interaction in the crust of neutron stars. We demonstrate and validate the method with Gross-Pitaevskii–like equations for the unitary Fermi gas, and demonstrate how the technique of adiabatic state preparation with time-dependent simulation can be used to calculate vortex-pinning interactions in fermionic systems such as the vortex-nucleus interaction in the crust of neutron stars.

We examine the millicharged dark matter scenario from a string theory perspective. In this scenario, kinetic and mass mixings of the photon with extra $U(1)$ bosons are claimed to give rise to small electric charges, carried by dark matter particles, whose values are determined by continuous parameters of the theory. This seems to contradict folk theorems of quantum gravity that forbid the existence of irrational charges in theories with a single massless gauge field. By considering the underlying structure of the $U(1)$ mass matrix that appears in type II string compactifications, we show that millicharges arise exclusively through kinetic mixing, and require the existence of at least two exactly massless gauge bosons.

There is an approximately 9% discrepancy, corresponding to $2.4\sigma$, between two independent constraints on the expansion rate of the Universe: one indirectly arising from the cosmic microwave background and baryon acoustic oscillations and one more directly obtained from local measurements of the relation between redshifts and distances to sources. We argue that by taking into account the local gravitational potential at the position of the observer this tension—strengthened by the recent Planck results—is partially relieved and the concordance of the Standard Model of cosmology increased. We estimate that measurements of the local Hubble constant are subject to a cosmic variance of about 2.4% (limiting the local sample to redshifts $z>0.010$) or 1.3% (limiting it to $z>0.023$), a more significant correction than that taken into account already. Nonetheless, we show that one would need a very rare fluctuation to fully explain the offset in the Hubble rates. If this tension is further strengthened, a cosmology beyond the Standard Model may prove necessary.

Intermediate-energy Coulomb excitation measurements are performed on the $N\ge 40$ neutron-rich nuclei ${}^{66,68}\mathrm{Fe}$ and ${}^{64}\mathrm{Cr}$. The reduced transition matrix elements providing a direct measure of the quadrupole collectivity $B(E2;2_1^{+}\to 0_1^{+})$ are determined for the first time in ${}^{68}\mathrm{Fe}_{42}$ and ${}^{64}\mathrm{Cr}_{40}$ and confirm a previous recoil distance method lifetime measurement in ${}^{66}\mathrm{Fe}_{40}$. The results are compared to state-of-the-art large-scale shell-model calculations within the full $fpgd$ neutron orbital model space using the Lenzi-Nowacki-Poves-Sieja effective interaction and confirm the results of the calculations that show these nuclei are well deformed.

We experimentally study the ground state coherence properties of cesium atoms in a nanofiber-based two-color dipole trap, localized $\sim 200\mathrm{nm}$ away from the fiber surface. Using microwave radiation to coherently drive the clock transition, we record Ramsey fringes as well as spin echo signals and infer a reversible dephasing time of $T_2^{*}=0.6\mathrm{ms}$ and an irreversible dephasing time of $T_2^{\prime }=3.7\mathrm{ms}$. By modeling the signals, we find that, for our experimental parameters, $T_2^{*}$ and $T_2^{\prime }$ are limited by the finite initial temperature of the atomic ensemble and the heating rate, respectively. Our results represent a fundamental step towards establishing nanofiber-based traps for cold atoms as a building block in an optical fiber quantum network.

We demonstrate 97%, 89%, and 76% transmission of sound amplitude in air through walls perforated with subwavelength holes of areal coverage fractions 0.10, 0.03, and 0.01, respectively, producing 94-, 950-, and 5700-fold intensity enhancements therein. This remarkable level of extraordinary acoustic transmission is achieved with thin tensioned circular membranes, making the mass of the air in the holes effectively vanish. Imaging the pressure field confirms incident-angle independent transmission, thus realizing a bona fide invisible wall. Applications include high-resolution acoustic sensing.

We generate a wide range of hexagonal sheet-based ZnO polymorphs inspired by enumeration of their characteristic underlying nets. Evaluating the bulk and nanofilm stabilities of these structures with ab initio calculations allows for an unprecedented overview of (nano)polymorphism in wurtzite materials. We find a rich low energy nanofilm polymorphism with a totally distinct stability ordering to that in the bulk. From this general basis we provide new insights into structural transitions observed during epitaxial growth and predictions for nanofilm stability with varying strain or thickness.

We present experimental evidence that the sticking probability of ${\mathrm{O}}_2$ on Al(111) depends strongly on the alignment of an ${\mathrm{O}}_2$ molecule relative to the surface. The steric effect was measured with an aligned ${\mathrm{O}}_2$ beam prepared by a hexapole magnet. It has been found that, at translational energies $<0.2\mathrm{eV}$, ${\mathrm{O}}_2$ sticking occurs predominantly when the molecular axis is parallel to the surface, and that the dissociation barrier at the perpendicular geometry is $\sim 0.1\mathrm{eV}$ higher than at the parallel geometry. The present results indicate that the abstraction process, which would occur at the perpendicular geometry, is a minor event at low translational energies.

Identifying the fingerprints of the Mott-Hubbard metal-insulator transition may be quite elusive in correlated metallic systems if the analysis is limited to the single particle level. However, our dynamical mean-field calculations demonstrate that the situation changes completely if the frequency dependence of the two-particle vertex functions is considered: The first nonperturbative precursors of the Mott physics are unambiguously identified well inside the metallic regime by the divergence of the local Bethe-Salpeter equation in the charge channel. In the low-temperature limit this occurs for interaction values where incoherent high-energy features emerge in the spectral function, while at high temperatures it is traceable up to the atomic limit.

First-principles calculations of the spin-orbit coupling in graphene with hydrogen adatoms in dense and dilute limits are presented. The chemisorbed hydrogen induces a giant local enhancement of spin-orbit coupling due to $s{p}^3$ hybridization which depends strongly on the local lattice distortion. Guided by the reduced symmetry and the local structure of the induced dipole moments, we use group theory to propose realistic minimal Hamiltonians that reproduce the relevant spin-orbit effects for both single-side semihydrogenated graphene (graphone) and for a single hydrogen adatom in a large supercell. The principal linear spin-orbit band splittings are driven by the breaking of the local pseudospin inversion symmetry and the emergence of spin flips on the same sublattice.

We present an infrared transmission spectroscopy study of the inter-Landau-level excitations in quasineutral epitaxial graphene nanoribbon arrays. We observed a substantial deviation in energy of the $L_{0(-1)}\to L_{1(0)}$ transition from the characteristic square root magnetic-field dependence of two-dimensional graphene. This deviation arises from the formation of an upper-hybrid mode between the Landau-level transition and the plasmon resonance. In the quantum regime, the hybrid mode exhibits a distinct dispersion relation, markedly different from that expected for conventional two-dimensional systems and highly doped graphene.

We theoretically investigated the anomalous Hall effect (AHE) and spin Hall effect (SHE) transversal to the insulating spacer I, in magnetic tunnel junctions of the form F/I/F where the F’s are ferromagnetic layers and I represents a tunnel barrier. We considered the case of purely ballistic (quantum mechanical) transport. These effects arise because of the asymmetric scattering of evanescent wave functions due to the spin-orbit interaction in the tunnel barrier. The AHE and SHE we investigated have a surface nature due to the proximity effect. Their amplitude is of first order in the scattering potential. This contrasts with ferromagnetic metals wherein these effects are of second (side-jump scattering) and third (skew scattering) order in these potentials. The value of the AHE current in the insulating spacer may be much larger than that in metallic ferromagnetic electrodes. For the antiparallel orientation of the magnetizations in the two F electrodes, a spontaneous Hall current exists even at zero applied voltage.

We demonstrate that the pattern forming partial differential equation derived from the auxin distribution model proposed by Meyerowitz, Traas, and others gives rise to all spiral phyllotaxis properties observed on plants. We show how the advancing pushed pattern front chooses spiral families enumerated by Fibonacci sequences with all attendant self-similar properties, a new amplitude invariant curve, and connect the results with the optimal packing based algorithms previously used to explain phyllotaxis. Our results allow us to make experimentally testable predictions.

We introduce a method for obtaining analytic approximations to the evolution of Markovian open quantum systems. It is based on resumming a generalized Dyson series in a way that ensures optimal convergence even in the absence of a small parameter. The power of this approach is demonstrated by two benchmark examples: the spatial detection of a free particle and the Landau-Zener problem in the presence of dephasing. The derived approximations are asymptotically exact and exhibit errors on the per mill level over the entire parameter range.

Jet reheating via nuclear collisions has recently been proposed as the main mechanism for gamma-ray burst (GRB) emission. In addition to producing the observed gamma rays, collisional heating must generate 10–100 GeV neutrinos, implying a close relation between the neutrino and gamma-ray luminosities. We exploit this theoretical relation to make predictions for possible GRB detections by $\mathrm{\text{IceCube}}+\mathrm{\text{DeepCore}}$. To estimate the expected neutrino signal, we use the largest sample of bursts observed by the Burst and Transient Source Experiment in 1991–2000. GRB neutrinos could have been detected if $\mathrm{\text{IceCube}}+\mathrm{\text{DeepCore}}$ operated at that time. Detection of 10–100 GeV neutrinos would have significant implications, shedding light on the composition of GRB jets and their Lorentz factors. This could be an important target in designing future upgrades of the $\mathrm{\text{IceCube}}+\mathrm{\text{DeepCore}}$ observatory.

We show that the Dirac-Born-Infeld conformal galileons, derived from the world-volume theory of a 3-brane moving in an anti–de Sitter bulk, admit a background, stable under quantum corrections, which violates the null energy condition. The perturbations around this background are stable and propagate subluminally. Unlike other known examples of null energy condition violation, such as ghost condensation and conformal galileons, this theory also admits a stable, Poincaré-invariant vacuum. The $2\to 2$ amplitude satisfies standard analyticity conditions. The full $S$ matrix is likely not analytic, however, since perturbations around deformations of the Poincaré invariant vacuum propagate superluminally.

We present a measurement of the direct $CP$-violating charge asymmetry in $B^{\pm }$ mesons decaying to $J/\psi K^{\pm }$ and $J/\psi {\pi }^{\pm }$ where $J/\psi$ decays to ${\mu }^{+}{\mu }^{-}$, using the full run II data set of $10.4{\mathrm{fb}}^{-1}$ of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. A difference in the yield of $B^{-}$ and $B^{+}$ mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of $A^{J/\psi K}=[0.59\pm 0.37]\%$, which is the most precise measurement to date, and $A^{J/\psi \pi }=[-4.2\pm 4.5]\%$. Both measurements are consistent with standard model predictions.

A first flavor-tagged measurement of the time-dependent $CP$-violating asymmetry in $B_s^0\to \varphi \varphi$ decays is presented. In this decay channel, the $CP$-violating weak phase arises due to $CP$ violation in the interference between $B_s^0\mathrm{\text{−}}{\overline{B}}_s^0$ mixing and the $b\to s\overline{s}s$ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$ and collected at a center-of-mass energy of 7 TeV with the LHCb detector, 880 $B_s^0\to \varphi \varphi$ signal decays are obtained. The $CP$-violating phase is measured to be in the interval $[-2.46,-0.76]\mathrm{rad}$ at a 68% confidence level. The $p$ value of the standard model prediction is 16%.