As an emerging ceramic material, recently synthesized nanotwinned diamond composites with various polytypes embedded in nanoscale twins exhibit unprecedented fracture toughness without sacrificing hardness. However, the toughening and crack healing mechanisms at the atomic scale and the associated crack propagation process of nanotwinned diamond composites remain mysterious. Here, we perform large-scale atomistic simulations of crack propagation in nanotwinned diamond composites to explore the underlying toughening and crack healing mechanisms in nanotwinned diamond composites. Our simulation results show that nanotwinned diamond composites have a higher fracture energy than single-crystalline and nanotwinned diamonds, which originates from multiple toughening mechanisms, including twin boundary and phase boundary impeding crack propagation, crack deflection and zigzag paths in nanotwins and sinuous paths in polytypes, and the formation of disordered atom clusters. More remarkably, our simulations reproduce more detailed crack propagation processes at the atomic scale, which is inaccessible by experiments. Moreover, our simulations reveal that crack healing occurs due to the rebonding of atoms on fracture surfaces during unloading and that the extent of crack healing is associated with whether the crack surfaces are clean. Our current study provides mechanistic insights into a fundamental understanding of toughening and crack healing mechanisms in nanotwinned diamond composites.

We show that Floquet chiral topological superconductivity arises naturally in Josephson junctions made of magnetic topological insulator-superconductor sandwich structures. The Josephson phase modulation associated with an applied bias voltage across the junction drives the system into the anomalous Floquet chiral topological superconductor hosting chiral Majorana edge modes in the quasienergy spectrum, with the bulk Floquet bands carrying zero Chern numbers. The bias voltage acts as a tuning parameter enabling novel Floquet topological quantum phase transitions driving the system into a myriad of exotic Majorana-carrying Floquet topological superconducting phases. Our theory establishes a new paradigm for realizing Floquet chiral topological superconductivity in solid-state systems, which should be experimentally directly accessible.

The ab initio Bethe-Salpeter equation (BSE) approach, an established method for the study of excitons in materials, is typically solved in a limit where only static screening from electrons is captured. Here, we generalize this framework to include dynamical screening from phonons at lowest order in the electron-phonon interaction. We apply this generalized BSE approach to a series of inorganic lead halide perovskites, $\mathrm{CsPb}{X}_3$, with $X=\mathrm{Cl}$, Br, and I. We find that inclusion of screening from phonons significantly reduces the computed exciton binding energies of these systems. By deriving a simple expression for phonon screening effects, we reveal general trends for their importance in semiconductors and insulators, based on a hydrogenic exciton model. We demonstrate that the magnitude of the phonon screening correction in isotropic materials can be reliably predicted using four material specific parameters: the reduced effective mass, static and optical dielectric constants, and frequency of the most strongly coupled longitudinal-optical phonon mode. This framework helps to elucidate the importance of phonon screening and its relation to excitonic properties in a broad class of semiconductors.

A central roadblock to analyzing quantum algorithms on quantum states is the lack of a comparable input model for classical algorithms. Inspired by recent work of the author [E. Tang, STOC 2019.], we introduce such a model, where we assume we can efficiently perform ${\ell }^2$-norm samples of input data, a natural analog to quantum algorithms that assume efficient state preparation of classical data. Though this model produces less practical algorithms than the (stronger) standard model of classical computation, it captures versions of many of the features and nuances of quantum linear algebra algorithms. With this model, we describe classical analogs to Lloyd, Mohseni, and Rebentrost’s quantum algorithms for principal component analysis [S. Lloyd, M. Mohseni, and P. Rebentrost, Nat. Phys. 10, 631 (2014).] and nearest-centroid clustering [S. Lloyd, M. Mohseni, and P. Rebentrost, Quantum algorithms for supervised and unsupervised machine learning]. Since they are only polynomially slower, these algorithms suggest that the exponential speedups of their quantum counterparts are simply an artifact of state preparation assumptions.

For the certification and benchmarking of medium-size quantum devices, efficient methods to characterize entanglement are needed. In this context, it has been shown that locally randomized measurements on a multiparticle quantum system can be used to obtain valuable information on the so-called moments of the partially transposed quantum state. This allows one to infer some separability properties of a state, but how to use the given information in an optimal and systematic manner has yet to be determined. We propose two general entanglement detection methods based on the moments of the partially transposed density matrix. The first method is based on the Hankel matrices and provides a family of entanglement criteria, of which the lowest order reduces to the known $p_3$-positive-partial-transpose criterion proposed in A. Elben et al. [Phys. Rev. Lett. 125, 200501 (2020)]. The second method is optimal and gives necessary and sufficient conditions for entanglement based on some moments of the partially transposed density matrix.

We develop two cutting-edge approaches to construct deep neural networks representing the purified finite-temperature states of quantum many-body systems. Both methods commonly aim to represent the Gibbs state by a highly expressive neural-network wave function, exemplifying the idea of purification. The first method is an entirely deterministic approach to generate deep Boltzmann machines representing the purified Gibbs state exactly. This strongly assures the remarkable flexibility of the ansatz which can fully exploit the quantum-to-classical mapping. The second method employs stochastic sampling to optimize the network parameters such that the imaginary time evolution is well approximated within the expressibility of neural networks. Numerical demonstrations for transverse-field Ising models and Heisenberg models show that our methods are powerful enough to investigate the finite-temperature properties of strongly correlated quantum many-body systems, even when the problematic effect of frustration is present.

We present limits on spin-independent dark matter-nucleon interactions using a 10.6 g Si athermal phonon detector with a baseline energy resolution of ${\sigma }_E=3.86\pm 0.04(\mathrm{stat}{)}_{-0.00}^{+0.19}(\mathrm{syst})\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from 93 to $140\mathrm{MeV}/c^2$, with a raw exposure of 9.9 g d acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches.

We describe an analysis comparing the $p\overline{p}$ elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in $pp$ collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV using a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of $\sqrt{s}=1.96\mathrm{TeV}$, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the $pp$ cross section. The two data sets disagree at the $3.4\sigma$ level and thus provide evidence for the $t$-channel exchange of a colorless, $C$-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same $C$-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in $pp$ scattering for which the significance is between $3.4\sigma$ and $4.6\sigma$. The combined significance is larger than $5\sigma$ and is interpreted as the first observation of the exchange of a colorless, $C$-odd gluonic compound.

We demonstrate an optical method for detecting the mechanical oscillations of an atom with single-phonon sensitivity. The measurement signal results from the interference between the light scattered by a trapped atomic ion and that of its mirror image. We detect the oscillations of the atom in the Doppler cooling limit and reconstruct average trajectories in phase space. We demonstrate single-phonon sensitivity near the ground state of motion after electronically induced transparency cooling. These results could be applied for motion detection of other light scatterers of fundamental interest, such as trapped nanoparticles.

We solve the large deviations of the Kardar-Parisi-Zhang (KPZ) equation in one dimension at short time by introducing an approach which combines field theoretical, probabilistic, and integrable techniques. We expand the program of the weak noise theory, which maps the large deviations onto a nonlinear hydrodynamic problem, and unveil its complete solvability through a connection to the integrability of the Zakharov-Shabat system. Exact solutions, depending on the initial condition of the KPZ equation, are obtained using the inverse scattering method and a Fredholm determinant framework recently developed. These results, explicit in the case of the droplet geometry, open the path to obtain the complete large deviations for general initial conditions.

We use a subignition scale laser, the 30 kJ Omega, and a novel shallow-cone target to study laser-plasma interactions at the ablation-plasma density scale lengths and laser intensities anticipated for direct drive shock-ignition implosions at National Ignition Facility scale. Our results show that, under these conditions, the dominant instability is convective stimulated Raman scatter with experimental evidence of two plasmon decay (TPD) only when the density scale length is reduced. Particle-in-cell simulations indicate this is due to TPD being shifted to lower densities, removing the experimental back-scatter signature and reducing the hot-electron temperature. The experimental laser energy-coupling to hot electrons was found to be 1%–2.5%, with electron temperatures between 35 and 45 keV. Radiation-hydrodynamics simulations employing these hot-electron characteristics indicate that they should not preheat the fuel in MJ-scale shock ignition experiments.

We offer a fractonic perspective on a familiar observation—a flat sheet of paper can be folded only along a straight line if one wants to avoid the creation of additional creases or tears. Our core underlying technical result is the establishment of a duality between the theory of elastic plates and a fractonic gauge theory with a second rank symmetric electric field tensor, a scalar magnetic field, a vector charge, and a symmetric tensor current. Bending moment and momentum of the plate are dual to the electric and magnetic fields, respectively. While the flexural waves correspond to the quadratically dispersing photon of the gauge theory, a fold defect is dual to its vector charge. Crucially, the fractonic condition constrains the latter to move only along its direction, i.e., the fold’s growth direction. By contrast, fracton motion in the perpendicular direction amounts to tearing the paper.

We present the first lattice QCD calculation of the distribution amplitudes of longitudinally and transversely polarized vector mesons $K^{*}$ and $\varphi$ using large momentum effective theory. We use the clover fermion action on three ensembles with $2+1+1$ flavors of highly improved staggered quarks action, generated by the MIMD Lattice Computation Collaboration, at physical pion mass and $\{0.06,0.09,0.12\}\mathrm{fm}$ lattice spacings and choose three different hadron momenta $P_z=\{1.29,1.72,2.15\}\mathrm{GeV}$. The resulting lattice matrix elements are nonperturbatively renormalized in a recently proposed hybrid scheme. An extrapolation to the continuum and infinite momentum limit is carried out. We find that, while the longitudinal distribution amplitudes tend to be close to the asymptotic form, the transverse ones deviate rather significantly from the asymptotic form. Our final results provide crucial ab initio theory inputs for analyzing pertinent exclusive processes.

Normalizing flows are a class of machine learning models used to construct a complex distribution through a bijective mapping of a simple base distribution. We demonstrate that normalizing flows are particularly well suited as a Monte Carlo integration framework for quantum many-body calculations that require the repeated evaluation of high-dimensional integrals across smoothly varying integrands and integration regions. As an example, we consider the finite-temperature nuclear equation of state. An important advantage of normalizing flows is the ability to build highly expressive models of the target integrand, which we demonstrate enables precise evaluations of the nuclear free energy and its derivatives. Furthermore, we show that a normalizing flow model trained on one target integrand can be used to efficiently calculate related integrals when the temperature, density, or nuclear force is varied. This work will support future efforts to build microscopic equations of state for numerical simulations of supernovae and neutron star mergers that employ state-of-the-art nuclear forces and many-body methods.

Residual stress has been empirically utilized for industrial applications to control material strength and shape of fragments. The interaction between the dynamically growing cracks and the residual stress field is sufficiently complicated to prevent us from building effective models. To rigorously evaluate the release and redistribution of residual stress in the dynamic fracture process, we develop a mathematical model and a numerical analysis method for the dynamic fracture in a residual stress field. Our methodology is simple and rigorous and applicable regardless of materials and scales.

We study acoustic streaming in liquids driven by a nondissipative acoustic body force created by light-induced temperature gradients. This thermoacoustic streaming produces a velocity amplitude nearly 100 times higher than the boundary-driven Rayleigh streaming and the Rayleigh-Bénard convection at a temperature gradient of $10\mathrm{K}/\mathrm{mm}$ in the channel. The Rayleigh streaming is altered by the acoustic body force at a temperature gradient of only $0.5\mathrm{K}/\mathrm{mm}$. The thermoacoustic streaming allows for modular flow control and enhanced heat transfer at the microscale. Our study provides the groundwork for studying microscale acoustic streaming coupled with temperature fields.

We study the geometric response of three-dimensional non-Hermitian crystalline systems with nontrivial point-gap topology. For systems with fourfold rotation symmetry, we show that in the presence of disclination lines with a total Frank angle, which is an integer multiple of $2\pi$, there can be nontrivial one-dimensional point-gap topology along the direction of the disclination lines. This results in disclination-induced non-Hermitian skin effects. By doubling a non-Hermitian Hamiltonian to a Hermitian three-dimensional chiral topological insulator, we show that the disclination-induced skin modes are zero modes of the effective surface Dirac fermion(s) in the presence of a pseudomagnetic flux induced by disclinations. Furthermore, we find that our results have a field theoretic description, and the corresponding geometric response actions (e.g., the Euclidean Wen-Zee action) enrich the topological field theory of non-Hermitian systems.