A single multimode fiber is considered an ideal optical element for endoscopic imaging due to the possibility of direct image transmission via multiple spatial modes. However, the wave distortion induced by the mode dispersion has been a fundamental limitation. In this Letter, we propose a method for eliminating the effect of mode dispersion and therefore realize wide-field endoscopic imaging by using only a single multimode fiber with no scanner attached to the fiber. Our method will potentially revolutionize endoscopy in various fields encompassing medicine and industry.

Compact laser-plasma accelerators can produce high energy electron beams with low emittance, high peak current but a rather large energy spread. The large energy spread hinders the potential applications for coherent free-electron laser (FEL) radiation generation. We discuss a method to compensate the effects of beam energy spread by introducing a transverse field variation into the FEL undulator. Such a transverse gradient undulator together with a properly dispersed beam can greatly reduce the effects of electron energy spread and jitter on FEL performance. We present theoretical analysis and numerical simulations for self-amplified spontaneous emission and seeded extreme ultraviolet and soft x-ray FELs based on laser plasma accelerators.

We use determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions to study thermodynamic properties and short-range spin correlations of fermions in the honeycomb lattice. We find that, at half filling and finite temperatures, nearest-neighbor spin correlations can be stronger in this lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid. The honeycomb lattice also exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We discuss the implications of these findings for optical lattice experiments.

We predict two spin-dependent transport phenomena in two-dimensional electron systems, which are induced by a spatially fluctuating Rashba spin-orbit interaction. When the electron gas is magnetized, the random Rashba interaction leads to the anomalous Hall effect. An example of such a system is a narrow-gap magnetic semiconductor-based symmetric quantum well. We show that the anomalous Hall conductivity reveals a strongly nonlinear dependence on the magnetization, decreasing exponentially at large spin density. We also show that electron scattering from a fluctuating Rashba field in a two-dimensional nonmagnetic electron system leads to a negative magnetoresistance arising solely due to spin-dependent effects.

Co-evolution exhibited by a network system, involving the intricate interplay between the dynamics of the network itself and the subsystems connected by it, is a key concept for understanding the self-organized, flexible nature of real-world network systems. We propose a simple model of such coevolving network dynamics, in which the diffusion of a resource over a weighted network and the resource-driven evolution of the link weights occur simultaneously. We demonstrate that, under feasible conditions, the network robustly acquires scale-free characteristics in the asymptotic state. Interestingly, in the case that the system includes dissipation, it asymptotically realizes a dynamical phase characterized by an organized scale-free network, in which the ranking of each node with respect to the quantity of the resource possessed thereby changes ceaselessly. Our model offers a unified framework for understanding some real-world diffusion-driven network systems of diverse types.

The minimum achievable statistical uncertainty in the estimation of physical parameters is determined by the quantum Fisher information. Its computation for noisy systems is still a challenging problem. Using a variational approach, we present an equation for obtaining the quantum Fisher information, which has an explicit dependence on the mathematical description of the noise. This method is applied to obtain a useful analytical bound to the quantum precision in the estimation of phase-shifts under phase diffusion, which shows that the estimation uncertainty cannot be smaller than a noise-dependent constant.

We demonstrate that the Rényi-2 entropy provides a natural measure of information for any multimode Gaussian state of quantum harmonic systems, operationally linked to the phase-space Shannon sampling entropy of the Wigner distribution of the state. We prove that, in the Gaussian scenario, such an entropy satisfies the strong subadditivity inequality, a key requirement for quantum information theory. This allows us to define and analyze measures of Gaussian entanglement and more general quantum correlations based on such an entropy, which are shown to satisfy relevant properties such as monogamy.

The photon spectrum in the inclusive electromagnetic radiative decays of the $B$ meson, $B\to X_s\gamma$ plus $B\to X_d\gamma$, is studied using a data sample of $(382.8\pm 4.2)\times {10}^6\mathit{{\rm Y}}(4S)\to B\overline{B}$ decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction $\mathcal{B}(B\to X_s\gamma )=(3.21\pm 0.33)\times {10}^{-4}$ for $E_{\gamma }>1.8\mathrm{GeV}$ and the direct $CP$ asymmetry $A_{CP}(B\to X_{s+d}\gamma )=0.057\pm 0.063$. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the $B$ meson rest frame.

We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range $150\mathrm{MeV}\le T\le 170\mathrm{MeV}$ the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%–15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.

We measure quantum beating patterns of photoelectron intensity caused by intramolecular vibrational energy redistribution following the excitation of a low-lying ring breathing state in $S_1$ parafluorotoluene. Analysis of the beating patterns reveals an exceptional sensitivity to details of the evolving wave packet which is found to contain two incoherent components, one of which rapidly dephases. This analysis enables the determination of coupling matrix elements, which are shown to depend strongly on torsional and rotational quantum numbers.

This experimental work focuses on the complex autoionization dynamics of ${\mathrm{Ar}}_2$ clusters below the first ionization energy of the argon atom. ${\mathrm{Ar}}_2$ is submitted to vacuum ultraviolet radiation, and the photoelectron spectra are collected in coincidence with the cluster ions. The ionization dynamics is revealed by the dependence on the photon energy. We applied a new experimental method which we developed to analyze the photoelectron signal. Thus, we were able (i) to get the complete vibrational progression of ${\mathrm{Ar}}_2^{+}$ that was never observed up to now, especially identifying the 0-0 transition overcoming the usual Franck-Condon limitations during single photoionization, and (ii) to obtain the projections of the vibrational wave functions of the autoionizing states over the ${\mathrm{Ar}}_2^{+}$ functions. This method provides a powerful tool to test the potential energy curves computed by high level theoretical calculations on Rydberg states.

Open quantum systems consisting of coupled bound and continuum states have been studied in a variety of physical systems, particularly within the scope of nuclear, atomic, and molecular physics. In the open systems, the effects of the continuum decay channels are accounted for by indirect non-Hermitian couplings among the quasibound states. Here we explore anti-Hermitian coupling in a plasmonic system for spatially manipulating light on the nanoscale. We show that by utilizing the anti-Hermitian coupling, plasmonic antennas closely packed within only $\lambda /15$ separations can be individually excited from the far field, which are otherwise indistinguishable from each other. This opens a new venue for the nanoscale lightwave control, wavelength multiplexing, and spectrum splitting.

We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion.

We compute spin transport in the unitary Fermi gas using the strong-coupling Luttinger-Ward theory. In the quantum degenerate regime the spin diffusivity attains a minimum value of $D_s\simeq 1.3\hslash /m$ approaching the quantum limit of diffusion for a particle of mass $m$. Conversely, the spin drag rate reaches a maximum value of ${\Gamma }_{\mathrm{sd}}\simeq 1.2k_B{T}_F/\hslash$ in terms of the Fermi temperature $T_F$. The frequency-dependent spin conductivity ${\sigma }_s(\omega )$ exhibits a broad Drude peak, with spectral weight transferred to a universal high-frequency tail ${\sigma }_s(\omega \to \infty )={\hslash }^{1/2}C/3\pi (m\omega {)}^{3/2}$ proportional to the Tan contact density $C$. For the spin susceptibility ${\chi }_s(T)$ we find no downturn in the normal phase.

High-pressure x-ray emission measurements are used to provide crucial evidence in the longstanding debate over the nature of the isostructural ($\alpha$, $\gamma$) volume collapse in elemental cerium. Extended local atomic model calculations show that the satellite of the $L\gamma$ emission line offers direct access to the total angular momentum observable $⟨J^2⟩$. This satellite experiences a 30% steplike decrease across the volume collapse, validating the Kondo model in conjunction with previous measurements. Direct comparisons are made with previous predictions by dynamical mean field theory. A general experimental methodology is demonstrated for analogous work on a wide range of strongly correlated $f$-electron systems.

Systems with strong spin-orbit coupling, which competes with other interactions and energy scales, offer a fertile playground to explore new correlated phases of matter. Weyl semimetals are an example where the phenomenon leads to a low-energy effective theory in terms of massless linearly dispersing fermions in three dimensions. In the absence of interactions chirality is a conserved quantum number, protecting the semimetallic physics against perturbations that are translationally invariant. In this Letter we show that the interplay between interaction and topology yields a novel chiral excitonic insulator. The state is characterized by a complex vectorial order parameter leading to a gapping out of the Weyl nodes. A striking feature is that it is ferromagnetic, with the phase of the order parameter determining the direction of the induced magnetic moment.

We study the electrolyte-gate-induced conductance at the surface of ${\mathrm{SrTiO}}_3(001)$. We find two distinct transport regimes as a function of gate voltage. At high carrier densities, a percolative metallic state is induced in which, at low temperatures, clear signatures of a Kondo effect are observed. At lower carrier densities, the resistance diverges at low temperatures and can be well described by a 2D variable range hopping model. We postulate that this derives from nonpercolative transport due to inhomogeneous electric fields from imperfectly ordered ions at the electrolyte-oxide interface.

The magnetic moment induced on Rh atoms, forming 1.6 nm average diameter clusters, embedded in an ${\mathrm{Al}}_2{\mathrm{O}}_3$ matrix, has been determined using x-ray magnetic circular dichroism measurements. The magnetic moment varies linearly with the applied magnetic field. At 2.3 K and under 17 T, the spin magnetic moment amounts to $0.067(2){\mu }_{\mathrm{B}}/\mathrm{Rh}$ atom. The orbital moment does not exceed 2% of the spin moment. The susceptibility is highly temperature dependent. This is in agreement with a prediction due to Moriya and Kawabata, that in itinerant electron systems, close to the onset of magnetism, the renormalization of the magnetic susceptibility by electron correlations, leads to a Curie-like behavior.

The coherent storage and phase modulation of x-ray single-photon wave packets in the resonant scattering of light off nuclei is theoretically investigated. We show that by switching off and on again the magnetic field in the nuclear sample, phase-sensitive storage of photons in the keV regime can be achieved. Corresponding $\pi$ phase modulation of the stored photon can be accomplished if the retrieving magnetic field is rotated by 180°. The development of such x-ray single-photon control techniques is a first step towards forwarding quantum optics and quantum information to shorter wavelengths and more compact photonic devices.

We study the collective dynamics of interacting paramagnetic colloids transported via a magnetic ratchet effect above a modulated periodic potential. Upon increasing the modulation frequency, the particles undergo a series of dynamic transitions, from a continuous smectic flow to a disorder flow, and later enter into a two phase flow regime, ending in a complete pinned state. In the disordered phase, the system organizes into density waves due to traffic jams, as in granular systems, while the two phase flow regime shows strong similarities with plastic flow in vortex matter. Finally, it is shown that induced attractive interactions between the moving colloids lead to enhancement of the particle current due to formation of condensed chains traveling along the modulated landscape.