Superconducting circuits and microwave signals are good candidates to realize quantum networks, which are the backbone of quantum computers. We have realized a quantum node based on a 3D microwave superconducting cavity parametrically coupled to a transmission line by a Josephson ring modulator. We first demonstrate the time-controlled capture, storage, and retrieval of an optimally shaped propagating microwave field, with an efficiency as high as 80%. We then demonstrate a second essential ability, which is the time-controlled generation of an entangled state distributed between the node and a microwave channel.

The spectrum of a bound state of three identical particles with a mass $m$ in a finite cubic box is studied. It is shown that in the unitary limit, the energy shift of a shallow bound state is given by $\mathrm{\Delta }E=c({\kappa }^2/m)(\kappa L{)}^{-3/2}|A{|}^2\exp (-2\kappa L/\sqrt{3})$, where $\kappa$ is the bound-state momentum, $L$ is the box size, $|A{|}^2$ denotes the three-body analog of the asymptotic normalization coefficient of the bound state wave function, and $c$ is a numerical constant. The formula is valid for $\kappa L\gg 1$.

The $N{\pi }^0{\pi }^0$ decays of positive-parity $N^{*}$ and ${\mathrm{\Delta }}^{*}$ resonances at about 2 GeV are studied at ELSA by photoproduction of two neutral pions off protons. The data reveal clear evidence for several intermediate resonances: $\mathrm{\Delta }(1232)$, $N(1520)3/2^{-}$, and $N(1680)5/2^{+}$, with spin parities $J^P=3/2^{+}$, $3/2^{-}$, and $5/2^{+}$. The partial wave analysis (within the Bonn-Gatchina approach) identifies $N(1440)1/2^{+}$ and the $N(\pi \pi {)}_{S\text{wave}}$ (abbreviated as $N\sigma$ here) as further isobars and assigns the final states to the formation of nucleon and $\mathrm{\Delta }$ resonances and to nonresonant contributions. We observe the known $\mathrm{\Delta }(1232)\pi$ decays of $\mathrm{\Delta }(1910)1/2^{+}$, $\mathrm{\Delta }(1920)3/2^{+}$, $\mathrm{\Delta }(1905)5/2^{+}$, $\mathrm{\Delta }(1950)7/2^{+}$, and of the corresponding spin-parity series in the nucleon sector, $N(1880)1/2^{+}$, $N(1900)3/2^{+}$, $N(2000)5/2^{+}$, and $N(1990)7/2^{+}$. For the nucleon resonances, these decay modes are reported here for the first time. Further new decay modes proceed via $N(1440)1/2^{+}\pi$, $N(1520)3/2^{-}\pi$, $N(1680)5/2^{+}\pi$, and $N\sigma$. The latter decay modes are observed in the decay of $N^{*}$ resonances and at most weakly in ${\mathrm{\Delta }}^{*}$ decays. It is argued that these decay modes provide evidence for a 3-quark nature of $N^{*}$ resonances rather than a quark-diquark structure.

An essential part of high-energy hadronic collisions is the soft hadronic activity that underlies the primary hard interaction. It includes soft radiation from the primary hard partons, secondary multiple parton interactions (MPI), and factorization-violating effects. The invariant mass spectrum of the leading jet in $Z+\mathrm{jet}$ and $H+\mathrm{jet}$ events is directly sensitive to these effects, and we use a QCD factorization theorem to predict its dependence on the jet radius $R$, jet $p_T$, jet rapidity, and partonic process for both the perturbative and nonperturbative components of primary soft radiation. We prove that the nonperturbative contributions involve only odd powers of $R$, and the linear $R$ term is universal for quark and gluon jets. The hadronization model in Pythia8 agrees well with these properties. The perturbative soft initial state radiation (ISR) has a contribution that depends on the jet area in the same way as the underlying event, but this degeneracy is broken by dependence on the jet $p_T$. The size of this soft ISR contribution is proportional to the color state of the initial partons, yielding the same positive contribution for $gg\to Hg$ and $gq\to Zq$, but a negative interference contribution for $q\overline{q}\to Zg$. Hence, measuring these dependencies allows one to separate hadronization, soft ISR, and MPI contributions in the data.

Based on data samples collected with the BESIII detector at the BEPCII collider at nine center of mass energies from 4.21 to 4.42 GeV, we search for the production of $e^{+}{e}^{-}\to \omega {\chi }_{cJ}$ ($J=0$, 1, 2). The process $e^{+}{e}^{-}\to \omega {\chi }_{c0}$ is observed for the first time, and the Born cross sections at $\sqrt{s}=4.23$ and 4.26 GeV are measured to be $(55.4\pm 6.0\pm 5.9)$ and $(23.7\pm 5.3\pm 3.5)\mathrm{pb}$, respectively, where the first uncertainties are statistical and the second are systematic. The $\omega {\chi }_{c0}$ signals at the other seven energies and the $e^{+}{e}^{-}\to \omega {\chi }_{c1}$ and $\omega {\chi }_{c2}$ signals are not significant, and the upper limits on the cross sections are determined. By examining the $\omega {\chi }_{c0}$ cross section as a function of center of mass energy, we find that it is inconsistent with the line shape of the $Y(4260)$ observed in $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$. Assuming the $\omega {\chi }_{c0}$ signals come from a single resonance, we extract the mass and width of the resonance to be $(4230\pm 8\pm 6)\mathrm{MeV}/c^2$ and $(38\pm 12\pm 2)\mathrm{MeV}$, respectively, and the statistical significance is more than $9\sigma$.

Direct measurements of ${\mathrm{Ar}}^{+}$ $1s^{-1}2p^{-1}nl$ double-core-hole shake-up states are reported using conventional single-channel photoemission, offering a new and relatively easy means to study such species. The high-quality results yield accurate energies and lifetimes of the double-core-hole states. Their photoemission spectrum also can be likened to $1s$ absorption of an exotic argon ion with a $2p$ core vacancy, providing new information about the spectroscopy of both this unusual ionic state as well as the neutral atom.

As an alternative to state-of-the-art laser frequency stabilization using ultrastable cavities, it has been proposed to exploit the nonlinear effects from coupling of atoms with a narrow transition to an optical cavity. Here, we have constructed such a system and observed nonlinear phase shifts of a narrow optical line by a strong coupling of a sample of strontium-88 atoms to an optical cavity. The sample temperature of a few mK provides a domain where the Doppler energy scale is several orders of magnitude larger than the narrow linewidth of the optical transition. This makes the system sensitive to velocity dependent multiphoton scattering events (Dopplerons) that affect the cavity field transmission and phase. By varying the number of atoms and the intracavity power, we systematically study this nonlinear phase signature which displays roughly the same features as for much lower temperature samples. This demonstration in a relatively simple system opens new possibilities for alternative routes to laser stabilization at the sub–100 mHz level and superradiant laser sources involving narrow-line atoms. The understanding of relevant motional effects obtained here has direct implications for other atomic clocks when used in relation to ultranarrow clock transitions.

Many-body theory is developed to calculate the $\gamma$ spectra for positron annihilation in noble-gas atoms. Inclusion of electron-positron correlation effects and core annihilation gives spectra in excellent agreement with experiment [K. Iwata et al., Phys. Rev. Lett. 79, 39 (1997)]. The calculated correlation enhancement factors ${\gamma }_{nl}$ for individual electron orbitals $nl$ are found to scale with the ionization energy $I_{nl}$ (in eV), as ${\gamma }_{nl}=1+\sqrt{A/I_{nl}}+(B/I_{nl}{)}^{\beta }$, where $A\approx 40\mathrm{eV}$, $B\approx 24\mathrm{eV}$, and $\beta \approx 2.3$.

We investigate the nonlinear interaction between a squeezed cavity mode and a mechanical mode in an optomechanical system (OMS) that allows us to selectively obtain either a radiation-pressure coupling or a parametric-amplification process. The squeezing of the cavity mode can enhance the interaction strength into the single-photon strong-coupling regime, even when the OMS is originally in the weak-coupling regime. Moreover, the noise of the squeezed mode can be suppressed completely by introducing a broadband-squeezed vacuum environment that is phase matched with the parametric amplification that squeezes the cavity mode. This proposal offers an alternative approach to control the OMS using a squeezed cavity mode, which should allow single-photon quantum processes to be implemented with currently available optomechanical technology. Potential applications range from engineering single-photon sources to nonclassical phonon states.

We study directed transport of charge and intrinsic angular momentum by periodically driven scattering in the regime of fast and strong driving. A spin-orbit coupling through a kicked magnetic field confined to a compact region in space leads to irregular scattering and triggers spin flips in a spatially asymmetric manner which allows us to generate polarized currents. The dynamical mechanisms responsible for the spin separation carry over to the quantum level and give rise to spin pumping. Our theory based on the Floquet formalism is confirmed by numerical solutions of the time-dependent inhomogeneous Schrödinger equation with a continuous source term.

We demonstrate that the universal mode driven by the density gradient in a plasma slab can be absolutely unstable even in the presence of reasonable magnetic shear. Previous studies from the 1970s that reached the opposite conclusion used an eigenmode equation limited to $L_x\gg {\rho }_i$, where $L_x$ is the scale length of the mode in the radial direction, and ${\rho }_i$ is the ion Larmor radius. Here we instead use a gyrokinetic approach which does not have this same limitation. Instability is found for perpendicular wave numbers $k_y$ in the range $0.7\lesssim k_y{\rho }_i\lesssim 100$, and for sufficiently weak magnetic shear: $L_s/L_n\gtrsim 17$, where $L_s$ and $L_n$ are the scale lengths of magnetic shear and density. Thus, the plasma drift wave in a sheared magnetic field may be unstable even with no temperature gradients, no trapped particles, and no magnetic curvature.

Energy loss in the transport of a beam of relativistic electrons in warm dense aluminum is measured in the regime of ultrahigh electron beam current density over $2\times {10}^{11}\mathrm{A}/{\mathrm{cm}}^2$ (time averaged). The samples are heated by shock compression. Comparing to undriven cold solid targets, the roles of the different initial resistivity and of the transient resistivity (upon target heating during electron transport) are directly observable in the experimental data, and are reproduced by a comprehensive set of simulations describing the hydrodynamics of the shock compression and electron beam generation and transport. We measured a 19% increase in electron resistive energy loss in warm dense compared to cold solid samples of identical areal mass.

We investigate the role of rattling guest atoms on the lattice thermal conductivity of a type-I clathrate ${\mathrm{Ba}}_8{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ by first-principles lattice dynamics. Comparing phonon properties of filled and empty clathrates, we show that rattlers cause tenfold reductions in the relaxation time of phonons by increasing the phonon-phonon scattering probability. Contrary to the resonant scattering scenario, the reduction in the relaxation time occurs in a wide frequency range, which is crucial for explaining the unusually low thermal conductivities of clathrates. We also find that the impact of rattlers on the group velocity of phonons is secondary because the flattening of phonon dispersion occurs only in a limited phase space in the Brillouin zone.

By using real-space renormalization group (RG) methods, we show that spin glasses in a field display a new kind of transition in high dimensions. The corresponding critical properties and the spin-glass phase are governed by two nonperturbative zero-temperature fixed points of the RG flow. We compute the critical exponents and discuss the RG flow and its relevance for three-dimensional systems. The new spin-glass phase we discovered has unusual properties, which are intermediate between the ones conjectured by droplet and full replica symmetry-breaking theories. These results provide a new perspective on the long-standing debate about the behavior of spin glasses in a field.

New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy, and interferometry, and so it is important to measure their properties with ease. Here, we show how one may immediately quantify these beams’ parameters without need for additional fabrication or nonstandard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation.

We study the adiabatic pumping of the Chern-Simons axion (CSA) coupling along a parametric loop characterized by a nonzero second Chern number $C^{(2)}$ from the viewpoint of the hybrid Wannier representation, in which the Wannier charge centers are visualized as sheets defined over a projected 2D Brillouin zone. We derive a new formula for the CSA coupling, expressing it as an integral involving Berry curvatures and potentials defined on the Wannier charge center sheets. We show that a loop characterized by a nonzero $C^{(2)}$ requires a series of sheet-touching events at which $2\pi$ quanta of Berry curvature are passed from sheet to sheet, in such a way that $e^2/h$ units of CSA coupling are pumped by a lattice vector by the end of the cycle. We illustrate these behaviors via explicit calculations on a model tight-binding Hamiltonian and discuss their implications.

Fractionalization of an electronic quasiparticle into spin, charge, and orbital parts is a fundamental and characteristic property of interacting electrons in one dimension. However, real materials are never strictly one dimensional and the fractionalization phenomena are hard to observe. Here we studied the spin and orbital excitations of the anisotropic ladder material ${\mathrm{CaCu}}_2{\mathrm{O}}_3$, whose electronic structure is not one dimensional. Combining high-resolution resonant inelastic x-ray scattering experiments with theoretical model calculations, we show that (i) spin-orbital fractionalization occurs in ${\mathrm{CaCu}}_2{\mathrm{O}}_3$ along the leg direction $x$ through the $xz$ orbital channel as in a 1D system, and (ii) no fractionalization is observed for the $xy$ orbital, which extends in both leg and rung direction, contrary to a 1D system. We conclude that the directional character of the orbital hopping can select different degrees of dimensionality. Using additional model calculations, we show that spin-orbital separation is generally far more robust than the spin-charge separation. This is not only due to the already mentioned selection realized by the orbital hopping, but also due to the fact that spinons are faster than the orbitons.

We have engineered electron-hole bilayers of inverted $\mathrm{InAs}/\mathrm{GaSb}$ quantum wells, using dilute silicon impurity doping to suppress residual bulk conductance. We have observed robust helical edge states with wide conductance plateaus precisely quantized to $2e^2/h$ in mesoscopic Hall samples. On the other hand, in larger samples the edge conductance is found to be inversely proportional to the edge length. These characteristics persist in a wide temperature range and show essentially no temperature dependence. The quantized plateaus persist to a 12 T applied in-plane field; the conductance increases from $2e^2/h$ in strong perpendicular fields manifesting chiral edge transport. Our study presents a compelling case for exotic properties of a one-dimensional helical liquid on the edge of $\mathrm{InAs}/\mathrm{GaSb}$ bilayers.