Quantum acoustics—a recently developed framework parallel to quantum optics—establishes a nonperturbative and coherent treatment of the electron-phonon interaction in real space. The quantum-acoustical representation reveals a displaced Drude peak hiding in plain sight within the venerable Fröhlich model: the optical conductivity exhibits a finite frequency maximum in the far-infrared range and the dc conductivity is suppressed. Our results elucidate the origin of the high-temperature absorption peaks in strange or bad metals, revealing that dynamical lattice disorder steers the system towards a non-Drude behavior.

We prove a general inequality between the charge current and its fluctuations valid for any weakly interacting coherent electronic conductor and for any stationary out-of-equilibrium condition, thereby going beyond established fluctuation-dissipation relations. The developed fluctuation-dissipation bound saturates at large temperature bias and reveals additional insight for heat engines, since it limits the output power by power fluctuations. It is valid when the thermodynamic uncertainty relations break down due to quantum effects and provides stronger constraints close to thermovoltage.

Qubits with predominantly erasure errors present distinctive advantages for quantum error correction (QEC) and fault-tolerant quantum computing. Logical qubits based on dual-rail encoding that exploit erasure detection have been recently proposed in superconducting circuit architectures, with either coupled transmons or cavities. Here, we implement a dual-rail qubit encoded in a compact, double-post superconducting cavity. Using an auxiliary transmon, we perform erasure detection on the dual-rail subspace. We characterize the behavior of the code space by a novel method to perform joint-Wigner tomography. This is based on modifying the cross-Kerr interaction between the cavity modes and the transmon. We measure an erasure rate of $3.981\pm 0.003(\mathrm{ms}{)}^{-1}$ and a residual, postselected dephasing error rate up to $0.17(\mathrm{ms}{)}^{-1}$ within the code space. This strong hierarchy of error rates, together with the compact and hardware-efficient nature of this novel architecture, holds promise in realizing QEC schemes with enhanced thresholds and improved scaling.

Based on $(10087\pm 44)\times {10}^{6}J/\psi$ events collected with the BESIII detector, a partial wave analysis of the decay $J/\psi \to \gamma K_S^0{K}_S^0{\eta }^{\prime }$ is performed. The mass and width of the $X(2370)$ are measured to be $2395\pm 11(\mathrm{stat}{)}_{-94}^{+26}(\mathrm{syst})\mathrm{MeV}/c^2$ and ${188}_{-17}^{+18}(\mathrm{stat}{)}_{-33}^{+124}(\mathrm{syst})\mathrm{MeV}$, respectively. The corresponding product branching fraction is $\mathcal{B}[J/\psi \to \gamma X(2370)]\times \mathcal{B}[X(2370)\to f_0(980){\eta }^{\prime }]\times \mathcal{B}[f_0(980)\to K_S^0{K}_S^0]=(1.31\pm 0.22(\mathrm{stat}{)}_{-0.84}^{+2.85}(\mathrm{syst}))\times {10}^{-5}$. The statistical significance of the $X(2370)$ is greater than $11.7\sigma$ and the spin parity is determined to be $0^{-+}$ for the first time. The measured mass and spin parity of the $X(2370)$ are consistent with the predictions of the lightest pseudoscalar glueball.

The ability to tailor with a high accuracy the intersite connectivity in a lattice is a crucial tool for realizing novel topological phases of matter. Here, we report the experimental realization of photonic dimer chains with long-range hopping terms of arbitrary strength and phase, providing a rich generalization of the Su-Schrieffer-Heeger model which, in its conventional form, is limited to nearest-neighbor couplings only. Our experiment is based on a synthetic dimension scheme involving the frequency modes of an optical fiber loop platform. This setup provides direct access to both the band dispersion and the geometry of the Bloch wave functions throughout the entire Brillouin zone allowing us to extract the winding number for any possible configuration. Finally, we highlight a topological phase transition solely driven by a time-reversal-breaking synthetic gauge field associated with the phase of the long-range hopping, providing a route for engineering topological bands in photonic lattices belonging to the AIII symmetry class.

Spectroscopy of correlated electron pairs was employed to investigate the energy dissipation process, as well as the transport and the emission of low-energy electrons on a polymethylmethacrylate surface, providing secondary electron spectra causally related to the energy loss of the primary. Two groups are identified in the cascade of slow electrons, corresponding to different stages in the energy dissipation process. The characteristic lengths for attenuation due to collective excitations and momentum relaxation are quantified for both groups and are found to be distinctly different: ${\lambda }_1=(12\pm 2)\AA$ and ${\lambda }_2=(62\pm 11)\AA$. The results strongly contradict the commonly employed model of exponential attenuation with the electron inelastic mean free path as characteristic length, but they essentially agree with a theory used for decades in astrophysics and neutron transport, albeit with characteristic lengths expressed in units of angstroms rather than light-years.

Using machine learning with a variational formula for diffusivity, we recast diffusion as a sum of individual contributions to diffusion—called “kinosons”—and compute their statistical distribution to model a complex multicomponent alloy. Calculating kinosons is orders of magnitude more efficient than computing whole trajectories, and it elucidates kinetic mechanisms for diffusion. The density of kinosons with temperature leads to new accurate analytic models for macroscale diffusivity. This combination of machine learning with diffusion theory promises insight into other complex materials.

The 8.4 eV nuclear isomer state in Th-229 is resonantly excited in Th-doped ${\mathrm{CaF}}_2$ crystals using a tabletop tunable laser system. A resonance fluorescence signal is observed in two crystals with different Th-229 dopant concentrations, while it is absent in a control experiment using Th-232. The nuclear resonance for the ${\mathrm{Th}}^{4+}$ ions in Th:${\mathrm{CaF}}_2$ is measured at the wavelength 148.3821(5) nm, frequency 2020.409(7) THz, and the fluorescence lifetime in the crystal is 630(15) s, corresponding to an isomer half-life of 1740(50) s for a nucleus isolated in vacuum. These results pave the way toward Th-229 nuclear laser spectroscopy and realizing optical nuclear clocks.

The shortest distance around the Universe through us is unlikely to be much larger than the horizon diameter if microwave background anomalies are due to cosmic topology. We show that observational constraints from the lack of matched temperature circles in the microwave background leave many possibilities for such topologies. We evaluate the detectability of microwave background multipole correlations for sample cases. Searches for topology signatures in observational data over the large space of possible topologies pose a formidable computational challenge.

Strong-field quantum electrodynamics (SF QED) is a burgeoning research topic dealing with electromagnetic fields comparable to the Schwinger field ($\approx 1.32\times {10}^{18}\mathrm{V}/\mathrm{m}$). While most past and proposed experiments rely on reaching this field in the rest frame of relativistic particles, the Schwinger limit could also be approached in the laboratory frame by focusing to its diffraction limit the light reflected by a plasma mirror irradiated by a multipetawatt laser. We explore the interaction between such intense light and matter with particle-in-cell simulations. We find that the collision with a relativistic electron beam would enable the study of the nonperturbative regime of SF QED, while the interaction with a solid target leads to a profusion of SF QED effects that retroact on the interaction. In both cases, relativistic attosecond pair jets with high densities are formed.

We formulate a Landau theory for altermagnets, a class of collinear compensated magnets with spin-split bands. Starting from the nonrelativistic limit, this Landau theory goes beyond a conventional analysis by including spin-space symmetries, providing a simple framework for understanding the key features of this family of materials. We find a set of multipolar secondary order parameters connecting existing ideas about the spin symmetries of these systems, their order parameters, and the effect of nonzero spin-orbit coupling. We account for several features of canonical altermagnets such as ${\mathrm{RuO}}_2$, MnTe, and ${\mathrm{CuF}}_2$ that go beyond symmetry alone, relating the order parameter to key observables such as magnetization, anomalous Hall conductivity, and magnetoelastic and magneto-optical probes. Finally, we comment on generalizations of our framework to a wider family of exotic magnetic systems derived from the zero spin-orbit coupled limit.

To produce ultimate high-brightness hadron beams, synchrotrons need to overcome a most prominent intensity limitation, i.e., space charge. This Letter characterizes the potential of pulsed electron lenses in detailed 3D tracking simulations, key to which is a realistic machine and space charge model. The space charge limit, imparted by betatron resonances, is shown to be increased by up to 50% using a low symmetric number of electron lenses in application to the Facility for Antiproton and Ion Research SIS100 synchrotron. Conceptually, a 100% increase is demonstrated with a larger number of electron lenses, which is found to rapidly saturate near the theoretical 2D limit.

At low Landau level filling factors ($\nu$), Wigner solid phases of two-dimensional electron systems in GaAs are pinned by disorder and exhibit a pinning mode, whose frequency is a measure of the disorder that pins the Wigner solid. Despite numerous studies spanning the past three decades, the origin of the disorder that causes the pinning and determines the pinning mode frequency remains unknown. Here, we present a study of the pinning mode resonance in the low-$\nu$ Wigner solid phases of a series of ultralow-disorder GaAs quantum wells which are similar except for their varying well widths $d$. The pinning mode frequencies $f_p$ decrease strongly as $d$ increases, with the widest well exhibiting $f_p$ as low as $\simeq 35\mathrm{MHz}$. The amount of reduction of $f_p$ with increasing $d$ can be explained remarkably well by tails of the wave function impinging into the alloy-disordered ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ barriers that contain the electrons. However, it is imperative that the model for the confinement and wave function includes the Coulomb repulsion in the growth direction between the electrons as they occupy the quantum well.

We observe that pretransitional order parameter fluctuations of a skyrmion-forming chiral nematic liquid crystal are slowed down for 4 orders of magnitude, if confined to $\lesssim 100\mathrm{nm}$ thin layers. Fluctuating fragments of half-skyrmions are observed in a narrow temperature interval and are explained by thermally activated hopping between the various energy states. Skyrmion fluctuations are accompanied by imbalanced topological charge: positive charges appear at higher temperatures and dominate in the fluctuating region until skyrmions fully condense and negative charges appear at lower temperatures.

The first measurement of the cross section for incoherent photonuclear production of $J/\psi$ vector mesons as a function of the Mandelstam $|t|$ variable is presented. The measurement was carried out with the ALICE detector at midrapidity, $|y|<0.8$, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. This rapidity interval corresponds to a Bjorken-$x$ range $(0.3–1.4)\times {10}^{-3}$. Cross sections are given in five $|t|$ intervals in the range $0.04<|t|<1{\mathrm{GeV}}^2$ and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a $|t|$ dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data.

Increasing accuracy of the theory and experiment of the $n=2$ ${}^3\mathrm{P}$ fine structure of helium has allowed for increasingly precise tests of quantum electrodynamics (QED), determinations of the fine-structure constant $\alpha$, and limitations on possible beyond the standard model physics. Here we present a 2 ppb measurement of the $J=1$ to $J=0$ interval. The measurement is performed using frequency-offset separated-oscillatory fields. Our result of 29 616 955 018(60) Hz represents a landmark for helium fine-structure measurements, and, for the first time, will allow for a 1-ppb determination of the fine-structure constant when QED theory for the interval is improved.

We report optical trapping of laser-cooled molecules at sufficient density to observe molecule-molecule collisions for the first time in a bulk gas. SrF molecules from a red-detuned magneto-optical trap (MOT) are compressed and cooled in a blue-detuned MOT. Roughly 30% of these molecules are loaded into an optical dipole trap with peak number density $n_0\approx 3\times {10}^{10}{\mathrm{cm}}^{-3}$ and temperature $T\approx 40\mathrm{\mu }\mathrm{K}$. We observe two-body loss with rate coefficient $\beta ={2.7}_{-0.8}^{+1.2}\times {10}^{-10}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$. Achieving this density and temperature opens a path to evaporative cooling towards quantum degeneracy of laser-cooled molecules.

We study fluctuations of the local energy cascade rate ${\mathrm{\Phi }}_{\ell }$ in turbulent flows at scales ($\ell$) in the inertial range. According to the Kolmogorov refined similarity hypothesis (KRSH), relevant statistical properties of ${\mathrm{\Phi }}_{\ell }$ should depend on ${\epsilon }_{\ell }$, the viscous dissipation rate locally averaged over a sphere of size $\ell$, rather than on the global average dissipation. However, the validity of KRSH applied to ${\mathrm{\Phi }}_{\ell }$ has not yet been tested from data. Conditional averages such as $⟨{\mathrm{\Phi }}_{\ell }|{\epsilon }_{\ell }⟩$ as well as of higher-order moments are measured from direct numerical simulations data, and results clearly adhere to the predictions from KRSH. Remarkably, the same is true when considering forward (${\mathrm{\Phi }}_{\ell }>0$) and inverse (${\mathrm{\Phi }}_{\ell }<0$) cascade events separately. Measured ratios of forward and inverse cascade probability densities conditioned on ${\epsilon }_{\ell }$ also confirm the applicability of the KRSH to analysis of the fluctuation relation from nonequilibrium thermodynamics.

The magnetic ground state of single crystalline ${\mathrm{RuO}}_2$ was investigated by the muon spin rotation and relaxation ($\mu \mathrm{SR}$) experiment. The spin precession signal due to the spontaneous internal magnetic field $B_{\mathrm{loc}}$, which is expected in the magnetically ordered phase, was not observed in the temperature range 5–400 K. Muon sites were evaluated by first-principles calculations using dilute hydrogen simulating muon as pseudohydrogen, and $B_{\mathrm{loc}}$ was simulated for the antiferromagnetic structures with a Ru magnetic moment $|{\mathit{m}}_{\mathrm{Ru}}|\approx 0.05{\mu }_{\mathrm{B}}$ suggested from diffraction experiments. As a result, the possibility was ruled out that muons are localized at sites where $B_{\mathrm{loc}}$ accidentally cancels. Conversely, assuming that the slow relaxation observed in $\mu \mathrm{SR}$ spectra was part of the precession signal, the upper limit for the magnitude of $|{\mathit{m}}_{\mathrm{Ru}}|$ was estimated to be $4.8(2)\times {10}^{-4}{\mu }_{\mathrm{B}}$, which is significantly less than $0.05{\mu }_{\mathrm{B}}$. These results indicate that the antiferromagnetic order, as reported, is unlikely to exist in the bulk crystal.

We study theoretically the dynamical process of yielding in cyclically sheared amorphous materials, within a thermal elastoplastic model and the soft glassy rheology model. Within both models we find an initially slow accumulation, over many cycles after the inception of shear, of low levels of damage in the form strain heterogeneity across the sample. This slow fatigue then suddenly gives way to catastrophic yielding and material failure. Strong strain localization in the form of shear banding is key to the failure mechanism. We characterize in detail the dependence of the number of cycles $N^{*}$ before failure on the amplitude of imposed strain, the working temperature, and the degree to which the sample is annealed prior to shear. We discuss our finding with reference to existing experiments and particle simulations, and suggest new ones to test our predictions.