We find quantum signatures of chaos in various metrics of information gain in quantum tomography. We employ a quantum state estimator based on weak collective measurements of an ensemble of identically prepared systems. The tomographic measurement record consists of a sequence of expectation values of a Hermitian operator that evolves under repeated application of the Floquet map of the quantum kicked top. We find an increase in information gain and, hence, higher fidelities in the reconstruction algorithm when the chaoticity parameter map increases. The results are well predicted by random matrix theory.

We study the effect of nonlinearity on systems with periodic parity-time ($PT$) symmetry, and show that nonlinearity can transform the system from broken to full $PT$ symmetry and vice versa. Furthermore, we show that even when the nonlinearity is insufficient to induce a transition from broken to full $PT$ symmetry, still, the wave functions neither decay nor diverge, despite the fact that the system has a complex eigenvalue spectrum. Rather, the amplitudes of the wavefunctions oscillate around the transition point. Our results apply to a wide variety of systems in optics and beyond.

An original approach is proposed here to reversibly tune Mie scattering resonances occurring in random media by means of external low induction magnetic fields. This approach is valid for both electromagnetic and acoustic waves. The experimental demonstration is supported by ultrasound experiments performed on emulsions made of fluorinated ferrofluid spherical droplets dispersed in a Bingham fluid. We show that the electromagnet-induced change of droplet shape into prolate spheroids, with a moderate aspect ratio of 2.5, drastically affects the effective properties of the disordered medium. Its effective acoustic attenuation coefficient is shown to vary by a factor of 5, by controlling both the flux density and orientation of the applied magnetic field.

We investigate the phase winding dynamics of a harmonically trapped two-component BEC subject to inhomogeneous Rabi oscillations between two pseudospin components. While the single-particle dynamics can be explained by mapping the system to a two-component Bose-Hubbard model, nonlinearities due to the interatomic repulsion lead to new effects observed in the experiments: In the presence of a linear magnetic field gradient, a qualitatively stable moving magnetic order that is similar to antiferromagnetic order is observed after critical winding is achieved. We also demonstrate how the phase winding can be used to generate copious dark-bright solitons in a two-component BEC, opening the door for new experimental studies of these nonlinear features.

Electron magnetohydrodynamic turbulence is investigated under the presence of a relatively strong external magnetic field $b_0{\mathbf{e}}_{\parallel }$ and through three-dimensional direct numerical simulations. Our study reveals the emergence of a $k_{\perp }^{-8/3}$ scaling for the magnetic energy spectrum at scales $k_{\parallel }^D\le k_{\perp }\le k_{\perp }^D$, where $k_{\parallel }^D$ and $k_{\perp }^D$ are, respectively, the typical largest dissipative scales along and transverse to the ${\mathbf{b}}_0$ direction. Unlike standard magnetohydrodynamic, this turbulence regime is characterized by filaments of electric currents parallel to ${\mathbf{b}}_0$. The anomalous scaling is in agreement with a heuristic model in which the transfer in the parallel direction is negligible. Implications for solar wind turbulence are discussed.

We experimentally demonstrate that hybrid plasmon-photon modes exist in a silver-coated glass bottle resonator. The bottle resonator is realized in a glass fiber with a smoothly varying diameter, which is subsequently coated with a rhodamine 800-dye doped acryl-glass layer and a 30 nm thick silver layer. We show by means of photoluminescence experiments supported by electromagnetic simulations that the rhodamine 800 photoluminescence excites hybrid plasmon-photon modes in such a bottle resonator, which provide a plasmon-type field enhancement at the outer silver surface and exhibit quality factors as high as 1000.

Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids such as water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.

We present a marker-free microscope that records the phase, amplitude, and polarization state of the field diffracted by the sample for different illumination directions. The data are processed with an appropriate inversion method to yield the sample permittivity map. We observe that the full-polarized information ameliorates significantly the three-dimensional image of weakly scattering subdiffraction objects. A resolution about one-fourth of the illumination wavelength is experimentally demonstrated on complex samples.

We propose solitons in a photonic topological insulator: self-localized wave packets forming topological edge states residing in the bulk of a nonlinear photonic topological insulator. These self-forming entities exhibit, despite being in the bulk, the property of unidirectional transport, similar to the transport their linear counterparts display on the edge of a topological insulator. In the concrete case of a Floquet topological insulator, such a soliton forms when a wave packet induces, through nonlinearity, a defect region in a honeycomb lattice of helical optical waveguides, and at the same time the wave packet populates a continuously rotating outer (or inner) edge state of that region. The concept is universal and applicable to topological systems with nonlinear response or mean-field interactions.

Osmosis describes the flow of water across semipermeable membranes powered by the chemical free energy extracted from salinity gradients. While osmosis can be expressed in simple terms via the van ’t Hoff ideal gas formula for the osmotic pressure, it is a complex phenomenon taking its roots in the subtle interactions occurring at the scale of the membrane nanopores. Here we use new opportunities offered by nanofluidic systems to create an osmotic diode exhibiting asymmetric water flow under reversal of osmotic driving. We show that a surface charge asymmetry built on a nanochannel surface leads to nonlinear couplings between water flow and the ion dynamics, which are capable of water flow rectification. This phenomenon opens new opportunities for water purification and complex flow control in nanochannels.

The transient appearance of bright spots in the beam profile of optical filaments formed in xenon is experimentally investigated. Fluence profiles are recorded with high-speed optical cameras at the kilohertz repetition rate of the laser source. A statistical analysis reveals a thresholdlike appearance of heavy-tailed fluence distributions together with the transition from single to multiple filamentation. The multifilament scenario exhibits near-exponential probability density functions, with extreme events exceeding the significant wave height by more than a factor of 10. The extreme events are isolated in space and in time. The macroscopic origin of these experimentally observed heavy-tail statistics is shown to be local refractive index variations inside the nonlinear medium, induced by multiphoton absorption and subsequent plasma thermalization. Microscopically, mergers between filament strings appear to play a decisive role in the observed rogue wave statistics.

Multiple scatterings occurring in a turbid medium attenuate the intensity of propagating waves. Here, we propose a method to efficiently deliver light energy to the desired target depth in a scattering medium. We measure the time-resolved reflection matrix of a scattering medium using coherent time-gated detection. From this matrix, we derive and experimentally implement an incident wave pattern that optimizes the detected signal corresponding to a specific arrival time. This leads to enhanced light delivery at the target depth. The proposed method will lay a foundation for efficient phototherapy and deep-tissue in vivo imaging in the near future.

A surface electromagnetic wave called the Dyakonov-Tamm wave has been theoretically predicted to exist at the interface of two dielectric materials at least one of which is both anisotropic and periodically nonhomogeneous. For experimental confirmation, a prism-coupled configuration was used to excite Dyakonov-Tamm waves guided by the interface of a dense thin film of magnesium fluoride and a chiral sculptured thin film of zinc selenide. The excitation was indicated by a reflection dip (with respect to the angle of incidence in the prism-coupled configuration) that is independent of the polarization state of the incident light as well as the thicknesses of both partnering materials beyond some thresholds. Applications to optical sensing and long-range on-chip communication are expected.

We report the experimental implementation and theoretical analysis of a random laser system that constitutes an amplifying periodic-on-average random superlattice (PARS). The stringent conditions on monodispersity required for a periodic-on-average random superlattice system are fulfilled using a linear array of spherical microresonators whose separation and size distribution can be controlled. Statistical studies of the lasing frequency reveal a frequency-controlled behavior. We perform transfer matrix calculations with gain to analyze the origin of the lasing modes, their thresholds, and frequency statistics. The results confirm that the experimentally observed lasing modes arise from states introduced into the stop gap of the underlying periodic system. On virtue of the fact that these high-quality gap states are restricted to a band of frequencies, the consequent random lasing exhibits significant reduction in frequency fluctuations.

A method for arbitrarily controlling the phase progression and power flow of electromagnetic fields within a region of space is introduced. Specifically, we describe how a 2D inhomogeneous, anisotropic medium can be designed that supports desired spatial distributions of the wave vector and Poynting vector direction. Plane-wave relations in anisotropic media are used in conjunction with an impedance matching process to find the required material parameters. The developed formulation allows one to independently tailor the phase and amplitude of a field profile. The work will find application in the design of electromagnetic or optical guiding structures and radiating apertures.

Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization $>36\%$. Analysis reveals only $2.1\pm 0.6\mathrm{eV}/\mathrm{atom}$ of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state.

Excitable localized states, spatial structures which possess both the features of temporal excitable pulses and of transverse cavity solitons, have been theoretically predicted in model systems as single pulses of light localized in space with a finite and deterministic duration. We study experimentally the nucleation of laser localized structures on a device defect and its motion along a spatial gradient. We demonstrate that in the reference frame of the drifting localized structure, the resulting dynamics presents the typical features of excitable systems. In particular, for specific parameter values, we observe that the nucleation of laser localized structures is triggered by noise, while the drift of the localized structure up to a spatial region where it vanishes provides the deterministic orbit which brings the system back to its initial rest state. The control of such structures may open the way to novel applications of localized structures beyond that of simple stationary bits.

The van der Pol oscillator is the prototypical self-sustained oscillator and has been used to model nonlinear behavior in biological and other classical processes. We investigate how quantum fluctuations affect phase locking of one or many van der Pol oscillators. We find that phase locking is much more robust in the quantum model than in the equivalent classical model. Trapped-ion experiments are ideally suited to simulate van der Pol oscillators in the quantum regime via sideband heating and cooling of motional modes. We provide realistic experimental parameters for ${}^{171}\mathrm{Yb}^{+}$ achievable with current technology.

We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems.