The non-Bloch topology leads to the emergence of various counterintuitive phenomena in non-Hermitian systems under the open boundary condition, which can not find a counterpart in Hermitian systems. However, in the non-Hermitian system without chiral symmetry, being ubiquitous in nature, exploring its non-Bloch topology has so far eluded experimental effort. Here, by introducing the concept of nonchiral non-Bloch invariants, we theoretically predict and experimentally identify the non-Bloch topological phase diagram of a one-dimensional (1D) non-Hermitian system without chiral symmetry in discrete-time nonunitary quantum walks of single photons. Interestingly, we find that such topological invariants not only can distinguish topologically distinct gapped phases, but they also faithfully capture the corresponding gap closing in open-boundary spectrum at the phase boundary. Different topological regions are experimentally identified by measuring the featured discontinuities of the higher moments of the walker’s displacement, which amazingly match excellently with our defined non-Bloch invariants. Our work provides a useful platform to study the interplay among topology, symmetries, and the non-Hermiticity.

Nanoscale objects moving relative to a thermal radiation bath experience a drag force due to the imbalance in their interaction with the blue- and redshifted components of the electromagnetic field. Here, we show that, in addition to this drag force, moving nanostructures with an anisotropic optical response experience a lateral force and a torque that substantially modify their trajectory. These phenomena emerge from the additional coupling between the electromagnetic field components polarized parallel and perpendicular to the trajectory, enabled by the anisotropic response of the nanostructure. This work unveils the intricate dynamics of anisotropic nanostructures moving in a thermal radiation bath.

A transverse radiative heat flux induced by the gradient of spin angular momentum of photons in nonreciprocal systems is predicted. This thermal analog of the inverse spin Hall effect is analyzed in magneto-optical networks exhibiting $C4$ symmetry, under the action of spatially variable external magnetic fields. This finding opens new avenues for thermal management and energy conversion with nonreciprocal systems through a localized and dynamic control of the spin angular momentum of light.

We propose a scheme allowing coherent shaping, i.e., controlling both the amplitude and phase, of attosecond x-ray pulses at free-electron lasers. We show that by seeding a free-electron laser with a short coherent seed that overfills the amplification bandwidth, one can shape the Wigner function of the pulse by controlling the undulator taper profile. The examples of controllable pulse pairs and trains, as well as isolated spectrotemporally shaped pulses with very broad bandwidths are examined in detail. Existing attosecond x-ray free-electron lasers can achieve these experimental conditions in a two-stage cascade, in which the seed is generated by a short current spike in an electron bunch and shaped in an unspoiled region within the same bunch. We experimentally demonstrate the production and control of phase-stable pulse trains using this method at the Linac Coherent Light Source II.

Isolated quantum many-body systems which thermalize under their own dynamics are expected to act as their own thermal baths, thereby losing memory of initial conditions and bringing their local subsystems to thermal equilibrium. Here we show that the infinite-dimensional limit of a quantum lattice model, as described by dynamical mean-field theory (DMFT), provides a natural framework to understand this self-consistent thermalization process. Using the Fermi-Hubbard model as a working example, we demonstrate that the emergence of a self-consistent bath occurs via a sharp thermalization front, moving ballistically and separating the initial condition from the long time thermal fixed point. We characterize the full DMFT dynamics through an effective temperature for which we derive a traveling wave equation of the Fisher-Kolmogorov-Petrovsky-Piskunov type. This equation allows for predicting the asymptotic shape of the front and its velocity, which match perfectly the full DMFT numerics. Our results provide a new angle to understand the onset of quantum thermalization in closed isolated systems.

The tunability of Dirac semimetals with antiferromagnetic Mn layers is of great interest. The observed sign change of interlayer magnetic coupling between ${\mathrm{CaMnBi}}_2$ and ${\mathrm{SrMnBi}}_2$ suggests ionic substitution as a potential tuning mechanism. If so, novel behavior near the compensation point could be expected. To explore this, we study a mixed-cation analog, ${\mathrm{Ca}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnSb}}_2$, where Bi is replaced by Sb. Conventional inelastic neutron scattering is impractical due to the small crystal size ($m\approx 0.28\mathrm{g}$) available for compositional studies; however, we find that using a neutron diffractometer with a wide-angle area detector we can obtain a good quality spin-wave signal, which is shaped by energy-momentum conservation and retains spectroscopic information even without direct energy analysis. Spin-wave modeling reveals an interlayer coupling quantitatively similar to ${\mathrm{SrMnSb}}_2$, indicating it is not directly tuned by ionic size and that the sign change in Bi-based compounds likely arises from the observed change in lattice symmetry. Beyond this key insight, our results present an efficient method for parametric and compositional studies of spin dynamics in small crystals.

Systems with nonreciprocal interactions generically display time-dependent states. These are routinely observed in finite systems, from neuroscience to active matter, in which globally ordered oscillations exist. However, the stability of these uniform nonreciprocal phases in noisy spatially-extended systems, their fate in the thermodynamic limit, and the critical behavior of the corresponding phase transitions are not fully understood. Here, we address these questions by introducing a nonreciprocal generalization of the Ising model and study its phase transitions by means of numerical and analytical approaches. While the mean-field equations predict three stable homogeneous phases (disordered, ordered, and a time-dependent swap phase), our large scale numerical simulations reveal a more complex picture. Static order is destroyed in any finite dimension due to the growth of rare droplets unless the symmetry between the two spin types is broken, triggering a stabilizing droplet-capture mechanism. The swap phase is destroyed by fluctuations in two dimensions through the proliferation of spiral defects but stabilized in three dimensions, where nonreciprocity changes the critical exponents from Ising to XY, thus giving rise to a robust spatially-distributed clock.

Protracted equilibration times and a multitude of competing periodically modulated structures are common characteristics of complex, self-assembled phases in block copolymer materials. These characteristics highlight the importance of designing processes to reproducibly direct the structure evolution of complex, spatially modulated structures. Using general symmetry considerations, we design a process that deterministically transforms the common, double-gyroid (DG) phase of linear diblock copolymers into a metastable A15 structure by irreversibly switching a conformationally symmetric $AB{B}^{\prime }$ diblock copolymer into an $AB{A}^{\prime }$ triblock copolymer. Key to the fabrication of the Frank-Kasper A15 structure is the nonmonotonic time evolution of the segregation that allows us to partition the large unit cell of the DG phase into 8 equivalent A15 units. Comparison between dynamic self-consistent field theory and particle-based simulations demonstrates the robustness of the designed pathway against thermal fluctuations and memory effects due to the underlying Rouse dynamics. Metastable structures that can be accessed from the DG phase are systematically explored as a function of molecular asymmetry and incompatibility.

Efficiently estimating the quantum Fisher information (QFI) is pivotal in quantum information science but remains an outstanding challenge for large systems due to its high nonlinearity. In this Letter, we tackle this long-standing challenge by integrating the Krylov subspace method–a celebrated tool from applied mathematics–into the framework of shadow tomography. The integrated technique, dubbed Krylov shadow tomography, enables us to formulate a strict hierarchy of nonpolynomial lower bounds on the QFI, among which the highest one matches the QFI exactly. We show that all the bounds can be expressed as expected values of the inverses of Hankel matrices, which are accessible via shadow tomography. Our Krylov shadow tomography therefore opens up a resource-efficient and experimentally feasible avenue to estimate not only nonpolynomial lower bounds but also the QFI itself.

In this Letter we propose a simple algebraic recursion for the complete one-loop integrands of $N$-graviton correlators. This formula automatically yields the correct symmetry factors of individual diagrams, taking into account both the graviton and the ghost loop, and seamlessly controlling the related combinatorics.

Invisible axion models that solve the strong $CP$ problem via the Peccei-Quinn (PQ) mechanism typically have a quality problem that arises from quantum gravity effects which violate all global symmetries. These models therefore require extreme fine-tuning of parameters for consistency. We present a new solution to the quality problem in a unified $\mathrm{SO}(10)\times {\mathrm{U}(1)}_a$ gauge model, where $\mathrm{U}(1{)}_a$ is an anomaly free axial gauge symmetry. PQ symmetry emerges as an accidental symmetry in this setup, which admits a PQ breaking scale as large as $7\times {10}^{11}\mathrm{GeV}$, allowing for the axion to be the cosmological dark matter. We call this a hybrid axion model due to its unique feature that it interpolates between the popular KSVZ and DFSZ axion models. Its predictions for the experimentally measurable axion couplings to the nucleon and electron are distinct from those of the usual models, a feature that can be used to test it. Furthermore, the model has no domain wall problem and it provides a realistic and predictive framework for fermion masses and mixings.

We propose a unique topological portal between quantum chromodynamics (QCD) and a dark sector characterized by a global symmetry breaking, which connects three QCD to two dark pions. When gauged, it serves as the leading portal between the two sectors, providing an elegant, self-consistent scenario of light thermal inelastic dark matter. The inherent antisymmetrization leads to diminished annihilations at later times and suppressed direct detection. However, novel collider signatures offer tremendous prospects for discovery at Belle II.

Polar polyatomic molecules provide an ideal but largely unexplored platform to encode qubits in rotational states. Here, we trap cold (100–600 mK) formaldehyde (${\mathrm{H}}_2\mathrm{CO}$) inside an electric box and perform a Ramsey-type experiment to observe long-lived ($\sim 100\mathrm{\mu s}$) coherences between symmetry-protected molecular states with opposite rotation but identical orientation, representing a quasi-hidden molecular degree of freedom. As a result, the observed qubit is insensitive to the magnitude of an external electric field and depends only weakly on magnetic fields. Our findings provide a basis for future quantum and precision experiments with trapped cold molecules.

Quantum simulation and metrology with atoms, ions, and molecules often rely on using light fields to manipulate their internal states. The absorbed momentum from the light fields can induce spin-orbit coupling and associated motional-induced (Doppler) dephasing, which may limit the coherence time available for metrology and simulation. We experimentally demonstrate the suppression of Doppler dephasing on a strontium optical clock transition by enabling atomic interactions through a shared mode in a high-finesse optical ring cavity. The interactions create a many-body energy gap that increases with atom number, suppressing motional dephasing when it surpasses the dephasing energy scale. This collective approach offers an alternative to traditional methods, like Lamb-Dicke confinement or Mössbauer spectroscopy, for advancing optical quantum sensors and simulations.

Quasicrystals are unique systems that, unlike periodic structures, lack translational symmetry but exhibit long-range order dramatically enriching the system properties. While evolution of light in the bulk of photonic quasicrystals is well studied, experimental evidences of light localization near the edge of truncated photonic quasicrystal structures are practically absent. In this Letter, we observe both linear and nonlinear localization of light at the edges of radially cropped quasicrystal waveguide arrays, forming an aperiodic Penrose tiling. Our theoretical analysis reveals that for certain truncation radii, the system exhibits linear eigenstates localized at the edge of the truncated array, whereas for other radii, this localization does not occur, highlighting the significant influence of truncation on edge light localization. Using single-waveguide excitations, we experimentally confirm the presence of localized states in Penrose arrays inscribed by a femtosecond laser and investigate the effects of nonlinearity on these states. Our theoretical findings identify a family of edge solitons, and experimentally, we observe a transition from linear localized states to edge solitons as the power of the input pulse increases. Our results represent the first experimental demonstration of localization phenomena induced by the selective truncation of quasiperiodic photonic systems.

We present the Magnetospheric Multiscale (MMS) mission’s observations of large-scale reconnection with a laminar ion exhaust containing many electron-scale filamentary current sheets, one of which exhibited a super-ion-Alfvénic electron jet flowing opposite to the ion exhaust jet, identified as electron-only reconnection. Despite the close proximity (a few electron inertial lengths) of the four MMS spacecraft, they recorded different electron-only reconnection signatures, including differences in the magnitude and profile of the electron jet, parallel electric fields, and dissipation $\mathbf{j}·{\mathbf{E}}^{\prime }\equiv \mathbf{j}·[\mathbf{E}+{\mathbf{v}}_{\mathrm{e}}\times \mathbf{B}]$, indicating extremely short-scale spatial and temporal variability. Furthermore, the leading spacecraft did not detect reconnection signatures, suggesting that MMS may have witnessed the onset of electron-only reconnection. Hall magnetic field perturbations associated with an electron-scale current sheet were detected after the onset. The dissipation $\mathbf{j}·{\mathbf{E}}^{\prime }$ in the electron-only current sheet was dominated by the component perpendicular to the magnetic field, contrasting with the dominance of the parallel component in previous large guide field reconnection events.