Measurements of the total and differential cross sections of Higgs boson production are performed using $20.3{\mathrm{fb}}^{-1}$ of $pp$ collisions produced by the Large Hadron Collider at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ and recorded by the ATLAS detector. Cross sections are obtained from measured $H\to \gamma \gamma$ and $H\to Z{Z}^{*}\to 4\ell$ event yields, which are combined accounting for detector efficiencies, fiducial acceptances, and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be ${\sigma }_{pp\to H}=33.0\pm 5.3(\text{stat})\pm 1.6(\text{syst})\mathrm{pb}$. The measurements are compared to state-of-the-art predictions.

We report an observation of the process $J/\psi \to \gamma X(1835)\to \gamma K_S^0{K}_S^0\eta$ at low $K_S^0{K}_S^0$ mass with a statistical significance larger than $12.9\sigma$ using a data sample of $1.31\times {10}^9$ $J/\psi$ events collected with the BESIII detector. In this region of phase space the $K_S^0{K}_S^0$ system is dominantly produced through the $f_0(980)$. By performing a partial wave analysis, we determine the spin parity of the $X(1835)$ to be $J^{PC}=0^{-+}$. The mass and width of the observed $X(1835)$ are $1844\pm 9(\mathrm{stat}{)}_{-25}^{+16}(\mathrm{syst})\mathrm{MeV}/c^2$ and $192_{-17}^{+20}(\mathrm{stat}{)}_{-43}^{+62}(\mathrm{syst})\mathrm{MeV}$, respectively, which are consistent with the results obtained by BESIII in the channel $J/\psi \to \gamma {\pi }^{+}{\pi }^{-}{\eta }^{\prime }$.

We show how to use two-mode squeezed light to exponentially enhance cavity-based dispersive qubit measurement. Our scheme enables true Heisenberg-limited scaling of the measurement, and crucially, it is not restricted to small dispersive couplings or unrealistically long measurement times. It involves coupling a qubit dispersively to two cavities and making use of a symmetry in the dynamics of joint cavity quadratures (a so-called quantum-mechanics-free subsystem). We discuss the basic scaling of the scheme and its robustness against imperfections, as well as a realistic implementation in circuit quantum electrodynamics.

We investigate the Loschmidt echo, the overlap of the initial and final wave functions of Luttinger liquids after a spatially inhomogeneous interaction quench. In studying the Luttinger model, we obtain an analytic solution of the bosonic Bogoliubov–de Gennes equations after quenching the interactions within a finite spatial region. As opposed to the power-law temporal decay following a potential quench, the interaction quench in the Luttinger model leads to a finite, hardly time-dependent overlap; therefore, no orthogonality catastrophe occurs. The steady state value of the Loschmidt echo after a sudden inhomogeneous quench is the square of the respective adiabatic overlaps. Our results are checked and validated numerically on the $XXZ$ Heisenberg chain.

We investigate the polaronic ground state of anatase ${\mathrm{TiO}}_2$ by bulk-sensitive resonant inelastic x-ray spectroscopy (RIXS) at the Ti $L_3$ edge. We find that the formation of the polaron cloud involves a single 95 meV phonon along the $c$ axis, in addition to the 108 meV $ab$-plane mode previously identified by photoemission. The coupling strength to both modes is the same within error bars, and it is unaffected by the carrier density. These data establish RIXS as a directional bulk-sensitive probe of electron-phonon coupling in solids.

We report the low-temperature magnetic properties of ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$, a rare-earth pyrochlore. Our susceptibility and magnetization measurements show that due to the thermal isolation of a Kramers doublet ground state, ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ has Ising-like magnetic moments of $\sim 1.18{\mu }_B$. The magnetic moments are confined to the local trigonal axes, as in a spin ice, but the exchange interactions are antiferromagnetic. Below 1 K, the system enters a regime with antiferromagnetic correlations. In contrast to predictions for classical $⟨111⟩$-Ising spins on the pyrochlore lattice, there is no sign of long-range ordering down to 0.02 K. Our results suggest that ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ features an antiferromagnetic liquid ground state with strong quantum fluctuations.

We report a new limitation on the ability of physical systems to perform computation—one that is based on generalizing the notion of memory, or storage space, available to the system to perform the computation. Roughly, we define memory as the maximal amount of information that the evolving system can carry from one instant to the next. We show that memory is a limiting factor in computation even in lieu of any time limitations on the evolving system—such as when considering its equilibrium regime. We call this limitation the space-bounded Church-Turing thesis (SBCT). The SBCT is supported by a simulation assertion (SA), which states that predicting the long-term behavior of bounded-memory systems is computationally tractable. In particular, one corollary of SA is an explicit bound on the computational hardness of the long-term behavior of a discrete-time finite-dimensional dynamical system that is affected by noise. We prove such a bound explicitly.

Some extensions of the standard model suggest the existence of vectorlike fermions whose mass $M$ can be larger by up to several orders of magnitude than the electroweak scale $v$, and with the Higgs mechanism providing only a small part $m$ of this mass that is a fraction of $v$. It is shown that in a certain range of the parameters $m$ and $M$, there exist stable globules of degenerate fermionic matter made from the lighter of the neutral vectorlike leptons (superheavy neutrinos) with a number density much larger than $m_h{v}^2$, with $m_h$ being the Higgs boson mass. The stability is due to the deformation of the Higgs field inside the globule to values greatly exceeding $v$. The globules are absolutely stable if the lighter of the vectorlike neutrinos is stable and can be (a part of) the dark matter.

We investigate the transport of excitations through a chain of atoms with nonlocal dissipation introduced through coupling to additional short-lived states. The system is described by an effective spin-$1/2$ model where the ratio of the exchange interaction strength to the reservoir coupling strength determines the type of transport, including coherent exciton motion, incoherent hopping, and a regime in which an emergent length scale leads to a preferred hopping distance far beyond nearest neighbors. For multiple impurities, the dissipation gives rise to strong nearest-neighbor correlations and entanglement. These results highlight the importance of nontrivial dissipation, correlations, and many-body effects in recent experiments on the dipole-mediated transport of Rydberg excitations.

We demonstrate an all-fiber cavity quantum electrodynamics system with a trapped single atom in the strong coupling regime. We use a nanofiber Fabry-Perot cavity, that is, an optical nanofiber sandwiched by two fiber-Bragg-grating mirrors. Measurements of the cavity transmission spectrum with a single atom in a state-insensitive nanofiber trap clearly reveal the vacuum Rabi splitting.

Wave scattering provides profound insight into the structure of matter. Typically, the ability to sense microstructure is determined by the ratio of scatterer size to probing wavelength. Here, we address the question of whether macroscopic waves can report back the presence and distribution of microscopic scatterers despite several orders of magnitude difference in scale between wavelength and scatterer size. In our analysis, monosized hard scatterers $5\mu \mathrm{m}$ in radius are immersed in lossless gelatin phantoms to investigate the effect of multiple reflections on the propagation of shear waves with millimeter wavelength. Steady-state monochromatic waves are imaged in situ via magnetic resonance imaging, enabling quantification of the phase velocity at a voxel size big enough to contain thousands of individual scatterers, but small enough to resolve the wavelength. We show in theory, experiments, and simulations that the resulting coherent superposition of multiple reflections gives rise to power-law dispersion at the macroscopic scale if the scatterer distribution exhibits apparent fractality over an effective length scale that is comparable to the probing wavelength. Since apparent fractality is naturally present in any random medium, microstructure can thereby leave its fingerprint on the macroscopically quantifiable power-law exponent. Our results are generic to wave phenomena and carry great potential for sensing microstructure that exhibits intrinsic fractality, such as, for instance, vasculature.

We report on a new method for realizing an exceptionally strong inertial confinement of a gas in a liquid: A centimetric spherical bubble filled with a reactive gaseous mixture in a liquid is expanded by an exothermic chemical reaction whose products condense in the liquid at the bubble wall. Hence, the cavity formed in this way is essentially empty as it collapses. The temperatures reached at maximum compression, inferred from the cavity radius dynamics and further confirmed by spectroscopic measurements exceed 20 000 K. Because the cavity is typically big, our findings also provide unique space and time resolved sequences of the events accompanying the collapse, notably the development of the inertial instability notoriously known to deter strong compression.

Using scanning tunneling microscopy and density functional theory, we show that the molecular ordering and orientation of metal phthalocyanine molecules on the deactivated Si surface display a strong dependency on the central transition-metal ion, driven by the degree of orbital hybridization at the heterointerface via selective $p-d$ orbital coupling. This Letter identifies a selective mechanism for modifying the molecule-substrate interaction which impacts the growth behavior of transition-metal-incorporated organic molecules on a technologically relevant substrate for silicon-based devices.

The insulating ground state of the $5d$ transition metal oxide ${\mathrm{CaIrO}}_3$ has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir $t_{2g}$ states exhibit large splittings and one-dimensional electronic states along the $c$ axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the $c$ direction via a superexchange interaction between ${\mathrm{Ir}}^{4+}$ spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the $t_{2g}$ states to open an insulating gap. These results indicate that ${\mathrm{CaIrO}}_3$ can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT $+$ dynamical mean field theory calculation, where the metal-insulator transition and the paramagnetic to AFM phase transition are concomitant with each other.

We show how an electrical measurement can detect the pairing of electrons on the same side of the Fermi surface (Amperian pairing), recently proposed by Patrick Lee for the pseudogap phase of high-$T_c$ cuprate superconductors. Bragg scattering from the pair-density wave introduces odd multiples of $2k_F$ momentum shifts when an electron incident from a normal metal is Andreev reflected as a hole. These Andreev-Bragg reflections can be detected in a three-terminal device, containing a ballistic $Y$ junction between normal leads (1, 2) and the superconductor. The cross-conductance $d{I}_1/d{V}_2$ has the opposite sign for Amperian pairing than it has either in the normal state or for the usual BCS pairing.