We experimentally investigate the dynamics of Josephson junctions between two confined exciton-polariton condensates when periodically modulated via self-induced GHz mechanical oscillations. We show that the energy detuning between the condensates displays a plateau behavior akin to the Shapiro steps when it matches the modulation quantum. At the step, massive tunneling of particles occurs, featuring Shapiro-like spikes with an asymmetric shape determined by the nonlinearities and gain present in this quantum driven-dissipative system.

In the quest for manipulating sound propagation, innovative approaches in acoustics, inspired by quantum phenomena, have yielded remarkable functionalities. Despite these advances in acoustics, the potential of supersymmetry, a powerful tool for shaping a system’s Hamiltonian, remains untapped. In this Letter, we demonstrate the application of supersymmetric transformations in acoustics through the creation of supersymmetric isophase acoustic potentials. Our theoretical exploration centers on isospectral supersymmetric transformations within an acoustic wave equation framework, enabling the generation of isophase acoustic potentials that preserve both transmission and reflection characteristics. Experimentally, we have developed a reconfigurable acoustic metamaterial platform to validate isophase scattering characteristics facilitated by the principles of supersymmetry. This design strategy offers a general method to create a family of continuously variable acoustic structures that remain indistinguishable under broadband acoustic wave probing, holding great promise for the future of sonar technology.

Free fermionic Gaussian, also known as matchgate, random circuits exhibit atypical behavior compared to generic interacting systems. They produce anomalously slow entanglement growth, characterized by diffusive scaling $S(t)\sim \sqrt{t}$, and evolve into volume-law entangled states at late times, $S\sim N$, which are highly unstable under measurements. Here, we investigate how doping such circuits with non-Gaussian resources (gates) restores entanglement structures of typical dynamics. We demonstrate that ballistic entanglement growth $S(t)\sim t$ is recovered after injecting an extensive total amount of non-Gaussian gates, which also restores Kardar-Parisi-Zhang fluctuations. When the evolution is perturbed with measurements, we uncover a measurement-induced phase transition between an area-law and a power-law entangled phase, $S\sim N^{\alpha }$, with $\alpha$ controlled by the doping. A genuine volume-law entangled phase is recovered only when non-Gaussian gates are injected at an extensive rate. Our findings bridge the dynamics of free and interacting fermionic systems, identifying non-Gaussianity as a key resource driving the emergence of nonintegrable behavior.

Multipartite entanglement offers a powerful framework for understanding the complex collective phenomena in quantum many-body systems that are often beyond the description of conventional bipartite entanglement measures. Here, we propose a class of multipartite entanglement measures that incorporate the matrix product state (MPS) representation, enabling the characterization of the optimality of quantum circuits for state preparation. These measures are defined as the minimal distances from a target state to the manifolds of MPSs with specified virtual bond dimensions $\chi$, and thus are dubbed as $\chi$-specified matrix product entanglement ($\chi$-MPE). We demonstrate superlinear, linear, and sublinear scaling behaviors of $\chi$-MPE with respect to the negative logarithmic fidelity $F$ in state preparation, which correspond to excessive, optimal, and insufficient circuit depth $D$ for preparing $\chi$-virtual-dimensional MPSs, respectively. Specifically, a linearly growing $\chi$-MPE with $F$ suggests ${\mathcal{H}}_{\chi }\simeq {\mathcal{H}}_D$, where ${\mathcal{H}}_{\chi }$ denotes the manifold of the $\chi$-virtual-dimensional MPSs and ${\mathcal{H}}_D$ denotes that of the states accessible by the $D$-layer circuits. We provide an exact proof that ${\mathcal{H}}_{\chi =2}\equiv {\mathcal{H}}_{D=1}$. Our results establish tensor networks as a powerful and general tool for developing parametrized measures of multipartite entanglement. The matrix product form adopted in $\chi$-MPE can be readily extended to other tensor network Ansätze, whose scaling behaviors are expected to assess the optimality of quantum circuit in preparing the corresponding tensor network states.

Snapshots—i.e., projective measurements of local degrees of freedom—are the most standard data taken in experiments on quantum simulators, usually to probe local physics. In this Letter we propose a simple protocol to experimentally probe physics of defects with these snapshots. Our protocol relies only on snapshots from the bulk system, without introducing the defect explicitly; as such, the physics of different kinds of defects can be probed using the same dataset. In particular, we demonstrate that, with snapshots of local spin configurations of, for example, the $1d$ Rydberg atom realization of the quantum Ising criticality, we can (1) extract the “defect entropy” and (2) access the continuous line of fixed points of effective defect conformal field theory.

An amplitude analysis of the $B^{+}\to ({\pi }^{+}{\pi }^{-})(K_{\mathrm{S}}^0{\pi }^{+})$ decay is performed in the mass regions $0.30<m_{{\pi }^{+}{\pi }^{-}}<1.10\mathrm{GeV}/c^2$ and $0.75<m_{K_{\mathrm{S}}^0{\pi }^{+}}<1.20\mathrm{GeV}/c^2$, using $pp$ collision data recorded with the LHCb detector corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. The polarization fractions and $CP$ asymmetries for $B^{+}\to \rho (770{)}^0{K}^{*}(892{)}^{+}$ decays are measured. Violation of the $CP$ symmetry in the decay $B^{+}\to \rho (770{)}^0{K}^{*}(892{)}^{+}$ is observed for the first time, with a significance exceeding 9 standard deviations. The $CP$ asymmetry is measured to be ${\mathcal{A}}_{CP}=0.507\pm 0.062(\mathrm{stat})\pm 0.024(\mathrm{syst})$ and the $CP$-averaged longitudinal polarization fraction of $f_L=0.720\pm 0.028(\mathrm{stat})\pm 0.009(\mathrm{syst})$. The measurements help to shed light on the polarization puzzle of $B$ mesons decaying to two vector mesons.

Searches are presented for $B_c^{+}\to D{h}^{+}{h}^{-}$ decays, where $D$ is a charmed meson and $h^{\pm }$ is a charged pion or kaon, using $pp$ collision data collected by the LHCb experiment corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. The decays $B_c^{+}\to D^{+}{K}^{+}{\pi }^{-}$, $B_c^{+}\to D^{*+}{K}^{+}{\pi }^{-}$, and $B_c^{+}\to D_s^{+}{K}^{+}{K}^{-}$ are observed for the first time. Their branching fractions, expressed as ratios relative to that of the $B_c^{+}\to B_s^0{\pi }^{+}$ decay, are determined to be $\mathcal{R}(B_c^{+}\to D^{+}{K}^{+}{\pi }^{-})=(1.96\pm 0.23\pm 0.08\pm 0.10)\times {10}^{-3}$, $\mathcal{R}(B_c^{+}\to D^{*+}{K}^{+}{\pi }^{-})=(3.67\pm 0.55\pm 0.24\pm 0.20)\times {10}^{-3}$, $\mathcal{R}(B_c^{+}\to D_s^{+}{K}^{+}{K}^{-})=(1.61\pm 0.35\pm 0.13\pm 0.07)\times {10}^{-3}$, where the first uncertainty is statistical, the second is systematic, and the third is due to the limited precision on the $D$-meson branching fractions. The decay channels proceed primarily through excited $K^0$ or $D^0$ resonances or $\varphi$ mesons, and open a new avenue for studies of charge-parity violation in beauty mesons.

We propose a novel strategy to systematically isolate the nucleon’s intrinsic nonperturbative three-dimensional structure by employing zero jettiness to suppress initial-state radiation in transverse-momentum-dependent observables. Applying this method to transverse single spin asymmetries (SSAs) in $W^{\pm }$ and $Z^0$ boson production at Relativistic Heavy Ion Collider (RHIC), we demonstrate a substantial enhancement of the asymmetry signal (e.g., by 115% for $W^{-}$ SSA at $q_{\perp }=5\mathrm{GeV}$). We show that this enhancement yields a substantial net gain in experimental sensitivity—even after accounting for the statistical cost of the veto—facilitating a more definitive test of the predicted Sivers function sign change. We further explore its applicability to spin-dependent measurements at the Electron-Ion Collider. Our analysis is formulated within a joint resummation framework that systematically resums large logarithms associated with both the veto scale and the gauge boson’s transverse momentum.

Compared to other stable isotopes of ${\mathrm{Yb}}^{+}$, ${}^{173}{\mathrm{Yb}}^{+}$ has a richer hyperfine structure, which leads to more favorable clock transitions, spectroscopic techniques for probing new physics, and more sophisticated quantum computing architectures. However, to date, its electronic spectrum remains poorly characterized. Here, we report on efficient laser cooling, state preparation, and detection of a single trapped ${{}^{173}\mathrm{Yb}}^{+}$ ion. The previously unobserved ${{}^{2}S}_{1/2}\to {{}^{2}D}_{3/2}$ electric quadrupole transition at 436 nm is coherently excited, and the isotope shift between ${{}^{171}\mathrm{Yb}}^{+}$ on this transition is determined with an uncertainty of 1.4 Hz. Using microwave spectroscopy, we resolve the hyperfine structure (HFS) of the ${{}^{2}D}_{3/2}$ state with a relative uncertainty below ${10}^{-8}$. From the HFS measurement data, we infer for ${}^{173}\mathrm{Yb}$ a nuclear magnetic octupole moment $\mathrm{\Omega }=-0.062(8)(\mathrm{b}\times {\mu }_N)$ with uncertainty reduced by more than 2 orders of magnitude compared to previous studies. The data also allow us to determine hyperfine anomalies for the ${{}^{2}S}_{1/2}$ and ${{}^{2}D}_{3/2}$ states.

We report the coherent excitation of the highly forbidden ${{}^{2}S}_{1/2}\to {{}^{2}F}_{7/2}$ clock transition in the odd isotope ${}^{173}{\mathrm{Yb}}^{+}$ with nuclear spin $I=5/2$, and reveal the hyperfine-state-dependent, nuclear-spin–induced quenching of this transition. The inferred lifetime of the $F_e=4$ hyperfine state is one order of magnitude shorter than the unperturbed ${{}^{2}F}_{7/2}$ clock state of ${}^{171}{\mathrm{Yb}}^{+}$. This reduced lifetime lowers the required optical power for coherent excitation of the clock transition, thereby reducing the ac Stark shift caused by the clock laser. Using a three-ion Coulomb crystal, we experimentally demonstrate an approximately twentyfold suppression of the ac Stark shift, a critical improvement for the scalability of future multi-ion ${\mathrm{Yb}}^{+}$ clocks. Furthermore, we report the $|{}^2{S}_{1/2},F_g=3⟩\to |{}^2{F}_{7/2},F_e=6⟩$ unquenched reference transition frequency as 642.11917656354(43) THz, along with the measured hyperfine splitting and calculated quadratic Zeeman sensitivities of the ${{}^{2}F}_{7/2}$ clock state. Our results pave the way toward multi-ion optical clocks and quantum computers based on ${}^{173}{\mathrm{Yb}}^{+}$.

Vortex $\gamma$ photons carrying orbital angular momenta (OAM) hold great potential for various applications. However, their generation remains a great challenge. Here, we successfully generate sub-MeV vortex $\gamma$ photons via all-optical inverse Compton scattering of relativistic electrons colliding with a subrelativistic Laguerre-Gaussian laser. In principle, directly measuring the OAM of $\gamma$ photons is challenging due to their incoherence and extremely short wavelength. Therein, we put forward a novel method to determine the OAM properties by revealing the quantum opening angle of vortex $\gamma$ photons, since vortex particles exhibit not only a spiral phase but also transverse momentum according to the quantum electrodynamics theory. Thus, $\gamma$ photons carrying OAM manifest a much larger angular distribution than those without OAM, which has been clearly observed in our experiments. This angular expansion is considered as an overall effect lying beyond classical theory. Our method provides the first experimental evidence for detecting vortex $\gamma$ photons and opens a new perspective for investigating OAM-induced quantum phenomena in broad fields.

Helicon waves (also known as whistler waves) satisfying the normal wave-particle cyclotron resonance are observed to limit the growth and maximum energy of relativistic electrons (REs) in low-density Ohmic DIII-D tokamak plasmas. Following the application of helicon waves, pitch-angle scattering of high-energy REs causes an increase in both synchrotron and electron-cyclotron emissions. The hard x-ray emission, a proxy for the RE population, ceases to grow. Energy-resolved hard x-ray measurements also show a striking decrease in the number of high-energy REs (above the resonance at approximately 8 MeV) to below the noise floor and an increase in low-energy ($\sim 4\mathrm{MeV}$) REs. This occurs despite the toroidal electric field remaining high enough to drive exponential RE growth in the absence of helicon waves. These results open new directions for limiting the maximum energy of RE populations in laboratory and fusion plasmas.

In type-II multiferroics, noncollinear spin textures are expected to induce electric polarization directly, leading to strong magnetoelectric coupling. Realizing such spin-driven multiferroicity in two-dimensional (2D) systems, and elucidating the interplay between local spins and electric polarization, are of both fundamental and technological importance. Here, using vectorial spin-polarized scanning tunneling microscopy, we investigated the spin-driven multiferroicity in monolayer ${\text{NiI}}_2$ at atomic scale. We identify a canted spin-spiral state with fully determined spin rotation plane, accompanied by a $2\mathit{Q}$ charge modulation. At spin-spiral domain walls, we discover topological spin textures that are composed of meron-antimeron pairs. These textures are associated with a distinct charge pattern and notable band shifts, indicating local bound charges induced by variations of ferroelectricity at domain wall. Our observations are well captured by a realistic spin model incorporating Kitaev interactions and a generalized spin-current model of type-II multiferroicity. The findings provide microscopic evidence of spin-driven multiferroicity in an extreme 2D system and establish a platform for low-dissipation, electric-field control of topological spin textures.

Studies of the 3D quantum Hall effect (QHE) have primarily emphasized transport features that mimic the well-established 2D QHE. In this Letter, we show that qualitatively new features arise when an in-plane magnetic field is applied to a 3D Weyl semimetal in the quantum Hall regime. An unexpected Hall quantum oscillation, distinct from the Weyl-orbit oscillation, coexists with the QHE, along with an unquantized two-terminal magnetoresistance. Moreover, longitudinal resistance, always deemed vanishing in QHE or generally positive, peculiarly becomes negative and remains disorder-robust. Quantization tunable by the lead configuration is further found in this transport geometry. A unique type of nonlocal quantum backscattering channels underlies these phenomena. Our Letter demonstrates a breakdown of the topological characterization of transport even with 3D Chern numbers and reveals hidden 3D QHE transport properties. It opens a new class of transport measurements and phenomena.

Spin-orbit torque efficiency is conventionally fixed by bulk materials. $D$-wave altermagnets introduce an additional nonrelativistic spin-charge conversion channel beyond the inverse spin-Hall effect. Using prototypical candidate ${\mathrm{RuO}}_2$ as an example, we show that the adjacent ferromagnet alone can dictate both the magnitude and sign of spin-charge conversion. Spin-pumping measurements on ${\mathrm{RuO}}_2/{\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ (YIG) and ${\mathrm{RuO}}_2/{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ (Py) bilayers yield opposite effective spin-Hall angles that persist across crystalline and polycrystalline ${\mathrm{RuO}}_2$. Inserting an ultrathin Au spacer at the ${\mathrm{RuO}}_2/\mathrm{YIG}$ interface reverses the signal, evidencing a dominant interfacial inverse Rashba-Edelstein effect, whereas ${\mathrm{RuO}}_2/\mathrm{Py}$ is governed by the bulk inverse spin-Hall effect. First-principles calculations trace this dichotomy to interface-selective band hybridization: Rashba surface states survive at the insulating YIG contact yet are quenched by metallic Py. Our findings establish ferromagnetic interfacing as a deterministic knob for tailoring spin-charge conversion in altermagnetic oxides, paving the way to field-free, low-dissipation spintronic memory devices.

We provide atomistic insights into the microscopic mechanism of polarization switching in wurtzite ferroelectric AlScN by integrating advanced thin-film fabrication, ferroelectric switching dynamics characterizations, high-resolution scanning transmission electron microscopy (STEM), and large-scale molecular dynamics simulations enabled by a deep neural network-based interatomic potential. Contrary to earlier interpretations proposing a transient nonpolar intermediate phase, our Letter provides strong evidence that the broad transitional regions previously observed in STEM images are consistent with projection artifacts resulting from the intrinsic three-dimensional zigzag morphology of 180° domain walls, which are a characteristic form of inversion domain boundary. This is further confirmed by STEM imaging of strategically prepared, partially switched ${\mathrm{Al}}_{0.75}{\mathrm{Sc}}_{0.25}\mathrm{N}$ thin films. Our simulations reveal that switching proceeds through collective, column-by-column atomic displacements, directly explaining the emergence of zigzag-shaped domain walls, and is consistent with the nucleation-limited switching behavior observed in experimental switching dynamic measurements. Furthermore, we show that increasing Sc content systematically lowers domain wall energy and associated nucleation barrier, thereby reducing the switching field in agreement with experimental trends. These findings establish a direct connection between local domain wall structure, switching dynamics, and macroscopic ferroelectric behavior.

Ergodicity, the property that all allowed configurations are explored over time, plays a pivotal role in explaining the equilibrium behavior of classical dynamical systems. Yet, such a property is typically precluded in quantum systems owing to stationary energy eigenstates. However, recent theoretical works have argued that ergodic explorations of the Hilbert space, occurring at varying levels as measured by statistical pseudorandomness of the time-evolved states, may happen for aperiodic driven quantum systems. Here, we experimentally investigate the hierarchy of Hilbert-space ergodicities (HSEs) achievable in the dynamics of a single spin. Through subjecting a nitrogen-vacancy center in diamond to various time-dependent modulations and continuously monitoring the spin trajectories with full state tomography, different degrees of HSE were observed, ranging from no HSE in a time-periodic drive, to partial HSE in a smoothly kicked time-quasiperiodic drive, to complete HSE in an aperiodic Fibonacci drive. We formulate a theoretical understanding of the increasing levels of HSE by attributing them to increasing levels of complexity associated with the drive sequences. Our Letter provides the first unambiguous experimental evidence of Hilbert space ergodicity, promoting deeper investigations into the mechanisms and fine-grained levels with which closed quantum systems reach equilibrium.

We present a simple theory accounting for two central observations in a recent experiment on quantum coarsening and collective dynamics on a programmable quantum simulator [Manovitz et al., Nature (London) 638, 86 (2025).]: an apparent speeding up of the coarsening process as the phase transition is approached and persistent oscillations of the order parameter after quenches within the ordered phase. Our theory, based on the Hamiltonian structure of the equations of motion in the classical limit of the quantum model, finds a speeding up already deep within the ordered phase, with subsequent slowing down as the domain wall tension vanishes upon approaching the critical line. Further, the oscillations are captured within a mean-field treatment of the order parameter field. For quenches within the ordered phase, small spatially varying fluctuations in the initial mean field lead to a remarkable long-time effect, wherein the system dynamically destroys its long-range order and has to coarsen to re-establish it. We term this phenomenon symmetry rebreaking, as the resulting late-time magnetization can have a sign opposite to the initial magnetization.