We generate pulsed, two-mode squeezed states in a single spatiotemporal mode with mean photon numbers up to 20. We directly measure photon-number correlations between the two modes with transition edge sensors up to 80 photons per mode. This corresponds roughly to a state dimensionality of 6400. We achieve detection efficiencies of 64% in the technologically crucial telecom regime and demonstrate the high quality of our measurements by heralded nonclassical distributions up to 50 photons per pulse and calculated correlation functions up to 40th order.

The existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can locally increase due to velocity space deformations of the particle velocity distribution function. These results support the idea that high-resolution measurements of the particle velocity distribution function are crucial for an accurate description of weakly collisional systems, such as the solar wind, in order to answer relevant scientific questions, related, for example, to particle heating and energization.

We investigate the decays of the excited $(b\overline{q})$ mesons as probes of the short-distance structure of the weak $\mathrm{\Delta }B=1$ transitions. These states are unstable under the electromagnetic or strong interactions, although their widths are typically suppressed by phase space. Compared to the pseudoscalar $B$ meson, the purely leptonic decays of the vector $B^{*}$ are not chirally suppressed and are sensitive to different combinations of the underlying weak effective operators. An interesting example is $B_s^{*}\to {\ell }^{+}{\ell }^{-}$, which has a rate that can be accurately predicted in the standard model. The branching fraction is $\mathcal{B}\sim 10^{-11}$, irrespective of the lepton flavor and where the main uncertainty stems from the unmeasured and theoretically not well known $B_s^{*}$ width. We discuss the prospects for producing this decay mode at the LHC and explore the possibility of measuring the $B_s^{*}\to \ell \ell$ amplitude, instead, through scattering experiments at the $B_s^{*}$ resonance peak.

We show through simulation that quantum interference in nonsequential double ionization can be used to control the recollision excitation with subsequent ionization (RESI) mechanism. This includes the shape, localization, and symmetry of RESI electron-momentum distributions, which may be shifted from a correlated to an anticorrelated distribution or vice versa, far below the direct ionization threshold intensity. As a testing ground, we reproduce recent experimental results by employing specific coherent superpositions of excitation channels. We examine two types of interference, from electron indistinguishability and intracycle events, and from different excitation channels. These effects survive focal averaging and transverse-momentum integration.

Recent heat-capacity experiments show quite unambiguously the existence of a liquid ${}^3\mathrm{He}$ phase adsorbed on graphite. This liquid is stable at an extremely low density, possibly one of the lowest found in nature. Previous theoretical calculations of the same system, and in strictly two dimensions, agree with the result that this liquid phase is not stable and the system is in the gas phase. We calculated the phase diagram of normal ${}^3\mathrm{He}$ adsorbed on graphite at $T=0$ using quantum Monte Carlo methods. Considering a fully corrugated substrate, we observe that at densities lower than $0.006{\AA }^{-2}$ the system is a very dilute gas that, at that density, is in equilibrium with a liquid of density $0.014{\AA }^{-2}$. Our prediction matches very well the recent experimental findings on the same system. On the contrary, when a flat substrate is considered, no gas-liquid coexistence is found, in agreement with previous calculations. We also report results on the different solid structures, and on the corresponding phase transitions that appear at higher densities.

We report on ultrasound and magnetization studies in three-dimensional, spin-dimerized ${\mathrm{Sr}}_3{\mathrm{Cr}}_2{\mathrm{O}}_8$ as a function of temperature and external magnetic field up to 61 T. It is well established [ , Phys. Rev. Lett. 103, 207203 (2009)] that this system exhibits a magnonic-superfluid phase between 30 and 60 T and below 8 K. By mapping ultrasound and magnetization anomalies as a function of magnetic field and temperature we establish that this superfluid phase is embedded in a domelike phase regime of a high-temperature magnonic liquid extending up to 18 K. Compared to thermodynamic results, our study indicates that the magnonic liquid could be characterized by an Ising-like order but has lost the coherence of the transverse components.

We investigate the rich morphologies of an electrically charged flexible ribbon, which is a prototype for many beltlike structures in biology and nanomaterials. Long-range electrostatic repulsion is found to govern the hierarchical buckling of the ribbon from its initially flat shape to its undulated and out-of-plane twisted conformations. In this process, the screening length is the key controlling parameter, suggesting that a convenient way to manipulate the ribbon morphology is simply to change the salt concentration. We find that these shapes originate from the geometric effect of the electrostatic interaction, which fundamentally changes the metric over the ribbon surface. We also identify the basic modes by which the ribbon reshapes itself in order to lower the energy. The geometric effect of the physical interaction revealed in this Letter has implications for the shape design of extensive ribbonlike materials in nano- and biomaterials.

We present the first experimental characterization of the azimuthal Wigner distribution of a photon. Our protocol fully characterizes the transverse structure of a photon in conjugate bases of orbital angular momentum (OAM) and azimuthal angle. We provide a test of our protocol by characterizing pure superpositions and incoherent mixtures of OAM modes in a seven-dimensional space. The time required for performing measurements in our scheme scales only linearly with the dimension size of the state under investigation. This time scaling makes our technique suitable for quantum information applications involving a large number of OAM states.

We study quantum electrodynamics in $d=3$ coupled to $N_f$ flavors of fermions. The theory flows to an IR fixed point for $N_f$ larger than some critical number $N_f^c$. For $N_f\le N_f^c$, chiral-symmetry breaking is believed to take place. In analogy with the Wilson-Fisher description of the critical $O(N)$ models in $d=3$, we make use of the existence of a fixed point in $d=4-2\epsilon$ to study the three-dimensional conformal theory. We compute, in perturbation theory, the IR dimensions of fermion bilinear and quadrilinear operators. For small $N_f$, a quadrilinear operator can become relevant in the IR and destabilize the fixed point. Therefore, the epsilon expansion can be used to estimate $N_f^c$. An interesting novelty compared to the $O(N)$ models is that the theory in $d=3$ has an enhanced symmetry due to the structure of 3D spinors. We identify the operators in $d=4-2\epsilon$ that correspond to the additional conserved currents at $d=3$ and compute their infrared dimensions.

The Higgs field in the standard model may couple to new physics sectors related to dark matter and/or massive neutrinos. In this Letter we propose a novel signature, the boosted di-Higgs-boson plus ${\cancel{E}}_T$ (which is either a dark matter or neutrino), to probe those new physics sectors. In a large class of models, in particular, the supersymmetric standard models and low scale seesaw mechanisms, this signature can play a key role. The signature has a clear background, and at the $\sqrt{s}=14\mathrm{TeV}$ high luminosity LHC, we can probe it with a production rate as low as $\sim 0.1\mathrm{fb}$. We apply it to benchmark models, supersymmetry in the bino-Higgsino limit, the canonical seesaw model, and the little Higgs model, finding that the masses of the Higgsino, right-handed neutrino, and heavy vector boson can be probed up to $\sim 500$, 650, and 900 GeV, respectively.

We report the first results of elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flow of charged particles in Pb-Pb collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region $|\eta |<0.8$ and for the transverse momentum range $0.2<p_T<5\mathrm{GeV}/c$. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multiparticle cumulant method. Compared to results from Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$, the anisotropic flow coefficients $v_2$, $v_3$, and $v_4$ are found to increase by $(3.0\pm 0.6)\%$, $(4.3\pm 1.4)\%$, and $(10.2\pm 3.8)\%$, respectively, in the centrality range 0%–50%. This increase can be attributed mostly to an increase of the average transverse momentum between the two energies. The measurements are found to be compatible with hydrodynamic model calculations. This comparison provides a unique opportunity to test the validity of the hydrodynamic picture and the power to further discriminate between various possibilities for the temperature dependence of shear viscosity to entropy density ratio of the produced matter in heavy-ion collisions at the highest energies.