We demonstrate the transition of a coupled electron shuttle from a stable to a strongly nonlinear response at room temperature. Within this transition we observe the coupled shuttle’s response to change from Coulomb controlled to conventional field emission. This parametric process is fully reversible and occurs within a broad frequency range. In combination, the large current and wide frequency band enable energy harvesting applications. The experimental data and the numerical calculations both indicate that the source of the nonlinearity is given by the electromechanical coupling of electron shuttling.

We present a measurement of form-factor-independent angular observables in the decay $B^0\to K^{*}(892{)}^0{\mu }^{+}{\mu }^{-}$. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared $q^2$ in the range $0.1<q^2<19.0{\mathrm{GeV}}^2/c^4$. Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one $q^2$ bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

We demonstrate highly efficient switching of optical signals between two optical fibers controlled by a single atom. The key element of our experiment is a whispering-gallery-mode bottle microresonator, which is coupled to a single atom and interfaced by two tapered fiber couplers. This system reaches the strong coupling regime of cavity quantum electrodynamics, leading to a vacuum Rabi splitting in the excitation spectrum. We systematically investigate the switching efficiency of our system, i.e., the probability that the fiber-optical switch redirects the light into the desired output. We obtain a large redirection efficiency reaching a raw fidelity of more than 60% without postselection. Moreover, by measuring the second-order correlation functions of the output fields, we show that our switch exhibits a photon-number-dependent routing capability.

In many complex systems, large events are believed to follow power-law, scale-free probability distributions so that the extreme, catastrophic events are unpredictable. Here, we study coupled chaotic oscillators that display extreme events. The mechanism responsible for the rare, largest events makes them distinct, and their distribution deviates from a power law. On the basis of this mechanism identification, we show that it is possible to forecast in real time an impending extreme event. Once forecasted, we also show that extreme events can be suppressed by applying tiny perturbations to the system.

Bit commitment is a fundamental cryptographic primitive in which Bob wishes to commit a secret bit to Alice. Perfectly secure bit commitment between two mistrustful parties is impossible through asynchronous exchange of quantum information. Perfect security is however possible when Alice and Bob split into several agents exchanging classical and quantum information at times and locations suitably chosen to satisfy specific relativistic constraints. Here we report on an implementation of a bit commitment protocol using quantum communication and special relativity. Our protocol is based on [A. Kent, Phys. Rev. Lett. 109, 130501 (2012)] and has the advantage that it is practically feasible with arbitrary large separations between the agents in order to maximize the commitment time. By positioning agents in Geneva and Singapore, we obtain a commitment time of 15 ms. A security analysis considering experimental imperfections and finite statistics is presented.

We present new limits on the allowed masses of a dark matter (DM) halo consisting of primordial black holes (PBH) (or any other massive compact halo object). We analyze two years of data from the Kepler satellite, searching for short-duration bumps caused by gravitational microlensing. After removing background events consisting of variable stars, flare events, and comets or asteroids moving through the Kepler field, we find no microlensing candidates. We measure the efficiency of our selection criteria by adding millions of simulated microlensing lensing events into the Kepler light curves. We find that PBH DM with masses in the range $2\times {10}^{-9}{M}_{\odot }$ to ${10}^{-7}{M}_{\odot }$ cannot make up the entirety of the DM in the Milky Way. At the low-mass end, this decreases the allowed mass range by more than an order of magnititude.

We present a lattice QCD computation of $\eta$ and ${\eta }^{\prime }$ masses and mixing angles, for the first time controlling continuum and quark mass extrapolations. The results for $M_{\eta }=551(8{)}_{\mathrm{stat}}(6{)}_{\mathrm{syst}}\mathrm{MeV}$ and $M_{{\eta }^{\prime }}=1006(54{)}_{\mathrm{stat}}(38{)}_{\mathrm{syst}}(+61{)}_{\mathrm{ex}}\mathrm{MeV}$ are in excellent agreement with experiment. Our data show that the mixing in the quark flavor basis can be described by a single mixing angle of $\varphi =46(1{)}_{\mathrm{stat}}(3{)}_{\mathrm{syst}}°$ indicating that the ${\eta }^{\prime }$ is mainly a flavor singlet state.

We report the direct detection of two metastable $\mathrm{H}(2{}^{2}S)$ atoms coming from the dissociation of a single cold ${\mathrm{H}}_2$ molecule, in coincidence measurements. The molecular dissociation was induced by electron impact in order to avoid limitations by the selection rules governing radiative transitions. Two detectors, placed close to the collision center, measure the neutral metastable $\mathrm{H}(2{}^{2}S)$ through a localized quenching process, which mixes the $\mathrm{H}(2{}^{2}S)$ state with the $\mathrm{H}(2{}^{2}P)$, leading to a Lyman-$\alpha$ detection. Our data show the accomplishment of a coincidence measurement which proves for the first time the existence of the $\mathrm{H}(2{}^{2}S)\mathrm{\text{−}}\mathrm{H}(2{}^{2}S)$ dissociation channel.

We study the effects of dipolar interactions on a Bose-Einstein condensate with synthetically generated Rashba spin-orbit coupling. The dipolar interaction we consider includes terms that couple spin and orbital angular momentum in a way perfectly congruent with the single-particle Rashba coupling. We show that this internal spin-orbit coupling plays a crucial role in the rich ground-state phase diagram of the trapped condensate. In particular, we predict the emergence of a thermodynamically stable ground state with a meron spin configuration.

We study quasi-two-dimensional dipolar Bose gases in which the bosons experience a Rashba spin-orbit coupling. We show that the degenerate dispersion minimum due to the spin-orbit coupling, combined with the long-range dipolar interaction, can stabilize a number of quantum crystalline and quasicrystalline ground states. Coupling the bosons to a fermionic species can further stabilize these phases. We estimate that the crystalline and quasicrystalline phases should be detectable in realistic dipolar condensates, e.g., dysprosium, and discuss their symmetries and excitations.

The reflection of light from the surface of an elastic solid gives rise to various types of elastic waves that propagate inside the solid. The weakest waves are generally those that are generated by the radiation pressure acting during the reflection of the light. Here, we present the first quantitative measurement of such light-pressure-induced elastic waves inside an ultrahigh-reflectivity mirror. Amplitudes of a few picometers were observed at the rear side of the mirror with a displacement-measuring conical piezoelectric sensor when laser pulses with a fluence of $1\mathrm{J}/{\mathrm{cm}}^2$ were reflected from the front side of the mirror.

We demonstrate the feasibility of levitating a small mirror using only radiation pressure. In our scheme, the mirror is supported by a tripod where each leg of the tripod is a Fabry-Perot cavity. The macroscopic state of the mirror is coherently coupled to the supporting cavity modes allowing coherent interrogation and manipulation of the mirror motion. The proposed scheme is an extreme example of the optical spring, where a mechanical oscillator is isolated from the environment and its mechanical frequency and macroscopic state can be manipulated solely through optical fields. We model the stability of the system and find a three-dimensional lattice of trapping points where cavity resonances allow for buildup of optical field sufficient to support the weight of the mirror. Our scheme offers a unique platform for studying quantum and classical optomechanics and can potentially be used for precision gravitational field sensing and quantum state generation.

We demonstrate the experimental implementation of an optical lattice that allows for the generation of large homogeneous and tunable artificial magnetic fields with ultracold atoms. Using laser-assisted tunneling in a tilted optical potential, we engineer spatially dependent complex tunneling amplitudes. Thereby, atoms hopping in the lattice accumulate a phase shift equivalent to the Aharonov-Bohm phase of charged particles in a magnetic field. We determine the local distribution of fluxes through the observation of cyclotron orbits of the atoms on lattice plaquettes, showing that the system is described by the Hofstadter model. Furthermore, we show that for two atomic spin states with opposite magnetic moments, our system naturally realizes the time-reversal-symmetric Hamiltonian underlying the quantum spin Hall effect; i.e., two different spin components experience opposite directions of the magnetic field.

We experimentally implement the Harper Hamiltonian for neutral particles in optical lattices using laser-assisted tunneling and a potential energy gradient provided by gravity or magnetic field gradients. This Hamiltonian describes the motion of charged particles in strong magnetic fields. Laser-assisted tunneling processes are characterized by studying the expansion of the atoms in the lattice. The band structure of this Hamiltonian should display Hofstadter’s butterfly. For fermions, this scheme should realize the quantum Hall effect and chiral edge states.

We explore the initial moments of impact between two dense granular clusters in a two-dimensional geometry. The particles are composed of solid ${\mathrm{CO}}_2$ and are levitated on a hot surface. Upon collision, the propagation of a dynamic “jamming front” produces a distinct regime for energy dissipation in a granular gas in which the translational kinetic energy decreases by over 90%. Experiments and associated simulations show that the initial loss of kinetic energy obeys a power law in time $\Delta E=-K{t}^{3/2}$, a form that can be predicted from kinetic arguments.

The boundary condition for gas flow at the solid-gas interface can be altered by in situ control of the state of a thin film adsorbed to the solid. A monolayer of ocatadecyltrichlorosilane (OTS) reversibly undergoes a meltinglike transition. When the temperature of an OTS-coated particle and plate is moved through the range of OTS “melting” temperatures, there is a change in the lubrication force between the particle and plate in 1 atm of nitrogen gas. This change is interpreted in terms of a change in the flow of gas mediated by the slip length and tangential momentum accommodation coefficient (TMAC). There is a minimum in slip length (290 nm) at $18°\mathrm{C}$, which corresponds to a maximum in TMAC (0.44). The slip length increases to 590 nm at $40°\mathrm{C}$ which corresponds to a TMAC of 0.25. We attribute the decrease in TMAC with increasing temperature to a decrease in roughness of the monolayer on melting, which allows a higher fraction of specular gas reflections, thereby conserving tangential gas momentum. The importance of this work is that it demonstrates the ability to control gas flow simply by altering the interface for fixed geometry and gas properties.

We present the first experimental microwave realization of the one-dimensional Dirac oscillator, a paradigm in exactly solvable relativistic systems. The experiment relies on a relation of the Dirac oscillator to a corresponding tight-binding system. This tight-binding system is implemented as a microwave system by a chain of coupled dielectric disks, where the coupling is evanescent and can be adjusted appropriately. The resonances of the finite microwave system yield the spectrum of the one-dimensional Dirac oscillator with and without a mass term. The flexibility of the experimental setup allows the implementation of other one-dimensional Dirac-type equations.

We demonstrate rotational excitation spectroscopy with the scanning tunneling microscope for physisorbed ${\mathrm{H}}_2$ and its isotopes HD and ${\mathrm{D}}_2$. The observed excitation energies are very close to the gas phase values and show the expected scaling with the moment of inertia. Since these energies are characteristic for the molecular nuclear spin states we are able to identify the para and ortho species of hydrogen and deuterium, respectively. We thereby demonstrate nuclear spin sensitivity with unprecedented spatial resolution.

We perform a quantitative, comparative study of the spin pumping, spin Seebeck, and spin Hall magnetoresistance effects, all detected via the inverse spin Hall effect in a series of over $20\mathrm{yttrium}\mathrm{iron}\mathrm{garnet}/\mathrm{Pt}$ samples. Our experimental results fully support present, exclusively spin current-based, theoretical models using a single set of plausible parameters for spin mixing conductance, spin Hall angle, and spin diffusion length. Our findings establish the purely spintronic nature of the aforementioned effects and provide a quantitative description, in particular, of the spin Seebeck effect.

The Alpha Magnetic Spectrometer experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter. Here, we make use of this high quality data to place stringent limits on dark matter with masses below $\sim 300\mathrm{GeV}$, annihilating or decaying to leptonic final states, essentially independent of the origin of this rise. We significantly improve on existing constraints, in some cases by up to 2 orders of magnitude.