The ultrafast dynamics of exciton-polaritons (EPs) in single plasmonic nanocavities are of fundamental interest due to extreme mode confinement ($V\sim {10}^{-6}{\lambda }^3$), which enables few-exciton strong coupling and strong nonlinearity of EPs. However, directly probing transient evolutions of EPs in a single nanocavity has remained a challenge. Here, we develop an EP-resonant enhanced ultrafast difference-frequency generation (DFG) microscopy for directly visualizing EP dynamics in a single ${\mathrm{WSe}}_2$-Au nanocavity. By scanning the pump photon energy across the polariton resonances and recording the DFG intensity as a function of pump-probe delay, we construct two-dimensional maps that directly visualize the transient evolution of the high and low energy branches of EPs. The maps reveal that the EPs collapse suddenly and then revive within 2 ps with a saturation threshold below 2 pJ, indicating strong nonlinearity of EPs in the few-exciton saturation regime. This Letter provides a new approach for visualizing the nonequilibrium dynamics of EPs in a single plasmonic nanocavity, offering important experimental evidence for ultrafast manipulation of EPs.

Attempts to understand multipartite quantum nonlocality are thwarted by the difficulty of devising quantum Bell inequalities (QBI) for systems composed of more than a few separate parties. In this Letter, we introduce the notion of tight connectors, a class of tensors which, if contracted according to some simple rules, result in tight QBIs. The new inequalities are saturated by tensor network states whose structure mimics the corresponding network of connectors. We further formulate the connector property of “full self-testing,” which singles out a subset of tight connectors whose associated QBIs can only be saturated (modulo local isometries) by probing the corresponding tensor network state with specific measurement operators. We provide large analytic families of tight, full self-testing connectors that allow for the generation, via contraction, of $N$-partite QBIs with a ratio between the maximum quantum and classical values that grows exponentially with $N$. In turn, our method provides a modular recipe for the generation of extremal quantum behaviors and associated tight bounds in arbitrarily large systems.

At lower energies, the resonances in scattering experiments are often isolated. In quantum chaotic many-body, disordered, or generically stochastic systems, the resonances overlap at larger energies. Eventually, the Ericson regime is reached in which the cross section behaves like a random function. The scattering-matrix elements then follow a universal Gaussian distribution. For more than 60 years, the emergence of this robust additional universal behavior on top of the universal system stochasticity has awaited a concise analytical treatment. We derive the transition to the Ericson regime in the universal Heidelberg approach and prove the universal Gaussian distribution by a proper asymptotic expansion. We also obtain explicit formulas for the moments and for the cross-section distribution. We compare with microwave experiments and numerical simulations.

We revisit the Caldeira-Leggett model of quantum Brownian motion with Ohmic spectral density, and derive an additional contribution to the decoherence kernel in a new high-temperature limit at arbitrarily large cutoff frequency. This contribution reveals a novel mechanism for the classicalization of high-frequency quantum fluctuations. We further demonstrate that it leads to a Markovian master equation that is in guaranteed Lindblad form, and argue that this master equation describes the correct Markovian limit of quantum Brownian motion. Our approach considers in detail the behavior of the decoherence kernel at both the initial and final times of the process on the timescale of the bath memory.

During the charging process, interactions between a quantum battery and its charger generally generate quantum correlations, which may reduce the amount of work extractable from the battery alone. We show that, by coupling the system with an environment that can be continuously monitored, one can weaken these correlations and enhance work extraction beyond what is achievable in the ideal (closed system) limit. This general mechanism is illustrated using both a cavity-mediated spin-spin and a Dicke quantum battery model.

We performed searches for $K_L\to {\pi }^0{\pi }^{0}X$ where $X$ may be an axionlike particle that promptly decays to two photons, and the first search for $K_L\to {\pi }^0{\pi }^0\gamma \gamma$ at the KOTO experiment using data taken in 2021. The search is performed for $X$ mass in the range of $160–220\mathrm{MeV}/c^2$. Three events were observed in the signal region, with two events near an $X$ mass of $177\mathrm{MeV}/c^2$. This result led to a range of upper limits on the branching ratio, $\mathrm{BR}(K_L\to {\pi }^0{\pi }^{0}X)$ $<(1-20)\times {10}^{-7}$ at the 95% confidence level (CL). No events were observed for the analysis of $K_L\to {\pi }^0{\pi }^0\gamma \gamma$, setting an upper limit on the branching ratio, $\mathrm{BR}(K_L\to {\pi }^0{\pi }^0\gamma \gamma )$ $<1.69\times {10}^{-6}$ at the 95% CL.

According to quantum chromodynamics, at sufficiently high energy, the structure of hadrons reveals a dynamic equilibrium between gluon splitting and gluon recombination—a phenomenon known as saturation. The process of diffractive photonuclear production of a $J/\psi$ vector meson provides a direct insight into the gluon composition of hadrons. The $J/\psi$ production as a function of momentum transferred in the interaction, quantified by the Mandelstam-$t$ variable, serves as an excellent probe for studying the structure of hadrons within the impact-parameter plane, because different ranges in $t$ are sensitive to the dynamics of the gluon field at varying spatial size scales. The ALICE Collaboration has measured the energy dependence of incoherent photonuclear production of $J/\psi$ mesons off lead ions, at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, for three Mandelstam-$t$ intervals. The energy dependence of the photonuclear cross section at the highest $|t|$ range measured, $(0.81<|t|<1.44){\mathrm{GeV}}^2$, is sensitive to subnucleonic structures of the Pb target. The increase of the cross section with energy at large $|t|$ shows evidence of suppression with respect to the increase seen at low $|t|$. The observed pattern of the energy evolution in data is similar to that of gluon saturation models.

An important validation of nucleosynthesis models of core-collapse supernovae is the comparison of radioisotope predictions to abundances inferred from observations of $\gamma$ rays emitted in remnants. One such isotope, ${}^{44}\mathrm{Ti}$, is especially sensitive to the ${}^{57}\mathrm{Ni}(p,\gamma ){}^{58}\mathrm{Cu}$ reaction rate. Despite this importance, no experimentally constrained rate exists for this reaction. It is thus crucial to determine this rate. GRETINA ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS) was used along with the first use of the Enge split-pole spectrograph at Notre Dame to measure structure properties of ${}^{58}\mathrm{Cu}$ via the ${}^{58}\mathrm{Ni}({}^3\mathrm{He},t){}^{58}\mathrm{Cu}$ reaction. The combined analysis of these complementary data sets allows for precise determination of ${}^{58}\mathrm{Cu}$ level energies, and spins are constrained from analysis of the $\gamma$-ray decay. ${}^{44}\mathrm{Ti}$ yields were found to change by over 25% compared to previous estimates in model calculations using the new experimentally constrained reaction rate.

We propose generating atom-atom three-body interactions in quantum gases by placing a quasi-two-dimensional Bose-Einstein condensate in front of two reflecting mirrors and illuminating it with dichromatic laser beams. These pumping fields traverse the condensate twice, thereby inducing a feedback effect on the atoms. We demonstrate that this optical feedback gives rise to an effective three-body interaction with unique long-range and nonreciprocal properties. Because of its long-range nature, this three-body interaction can give rise to various stable stationary droplet cluster states, as well as a distinct ring state that emerges through a purely self-organizing process. Furthermore, we show that the nonreciprocal nature of this interaction can lead to remarkable self-acceleration of the condensate. Additionally, our scheme offers a highly controllable setting, where pairwise two-body interactions can be tuned to vanish. This flexibility provides a promising route for exploring exotic physics associated with multibody interactions.

Percolative superconductivity frequently arises in two-dimensional van der Waals materials due to reduced dimensionality, enhanced quantum fluctuations, and complex electron-phonon interactions, providing a unique platform where normal electrons coexist with Cooper pairs. We report the observation of substantial third-order nonlinear transport in a trilayer $1T^{\prime }\text{−}{\text{MoTe}}_2$ superconductor within its percolative transition regime. The third-harmonic longitudinal voltage ($V_{\parallel }^{3\omega }$) exhibits a clear cubic dependence on excitation current below a threshold, with both its magnitude and nonlinear coefficient strongly correlated with the superconducting state. This nonlinear response is semiquantitatively captured by the superconducting fluctuation within the time-dependent Ginzburg-Landau theory, where nonlinear transport arises due to fluctuating Cooper pairs. Our results demonstrate that third-order nonlinear transport serves as a sensitive probe of superconducting transitions in percolative systems and establish a foundation for exploring higher-order transport phenomena in strongly correlated systems.

Topological insulators with bulk-boundary correspondence have been widely explored in condensed-matter, photonic, and phononic systems. Two-dimensional second-order topological insulators are typically characterized by zero-dimensional boundary states localized at sharp corners. While these corner bound states have been widely explored across multiple platforms as robust signatures of second-order topology, their strong confinement to sharp corners severely limits practical applications. Here, we experimentally demonstrate control over topological boundary states in a honeycomb-lattice acoustic second-order topological insulator. Specifically, we reveal that the boundary Dirac mass exhibits a sensitive and diverse dependence on the edge types, enabled by sublattice degrees of freedom. By engineering the edges, we achieve not only arbitrary spatial relocation of topological boundary states from their conventional corner positions, but also precise, continuous tuning of their wave-function profiles from bound to extended as desired. Our Letter establishes a universal approach for manipulating topological boundary states, offering possibilities for designing advanced acoustic devices.

Multipolar order, such as octupolar order, is a key concept in condensed matter physics, particularly in light of elusive hidden orders. However, its experimental identification remains challenging due to the absence of direct coupling to conventional external stimuli. In this Letter, we propose that dual-circular Raman scattering serves as a probe of multipolar anisotropies. By combining symmetry analysis with microscopic calculations, we identify that both time-reversal-even ($\theta$ -even) and time-reversal-odd ($\theta$ -odd) axial multipolar phases exhibit the sizable Raman optical activity as a direct consequence of multipolar symmetry breaking. The quantitative significance of the proposed response is demonstrated by the first-principles study of pyrite, a prototypical axial octupolar material. Furthermore, we reveal that a multipolar phonon, a three-dimensional and alternating displacement resembling the chiral phonon, plays a vital role in the proposed optical phenomena. Our findings open a pathway for identifying multipolar orders in various materials through dual-circular Raman spectroscopy as a sensitive and versatile probe.

Exciton-phonon interactions play a central role in defining the optical response of hexagonal boron nitride (hBN), yet their quantitative determination has remained incomplete. Here, we reveal the Fröhlich-type exciton-phonon coupling in boron-10-enriched hBN using low-temperature cathodoluminescence. We resolve the indirect exciton $5.95\pm 0.02\mathrm{eV}$ together with its longitudinal optical phonon replica detuned by $184\pm 56\mathrm{meV}$, enabling the extraction of a Fröhlich-coupling constant $\alpha =0.159$, and a larger exciton binding energy of 161 meV, larger than previously reported values for natural abundance hBN, which is attributed to isotope enrichment. The inferred polaron radius exceeds the lattice constant, indicating large-polaron behavior. We deduced an exciton scattering time $\sim 97\mathrm{fs}$ (homogeneous linewidth $\sim 6.76\mathrm{meV}$), a polaron binding energy of magnitude $\sim 48\mathrm{meV}$, and an effective mass of $1.045m_0$. These results provide a direct quantitative characterization of exciton-phonon coupling in isotopically engineered hBN and establish a foundation for tailoring its phonon-polaritonic and quantum-optical properties.

Understanding diffusion in disordered systems composed of obstacle particles is crucial for elucidating transport phenomena ranging from biological tissues to engineered porous materials. Existing studies predominantly employ the random sequential adsorption method and characterize media solely by density $\rho$. We show that this is fundamentally incomplete: These structures exhibit a tunable hyperuniformity exponent $\beta$ that spans from periodic lattices to Poisson processes, yielding qualitatively different diffusion even at identical $\rho$. We derive a $\beta$-dependent analytical expression for the diffusion coefficient $1-D/D_0\sim {\rho }^{2-\beta /2}$ in the low-$\rho$ limit and predict a $\beta$-dependent percolation threshold ${\rho }_c(\beta )$ in the high-$\rho$ regime. Brownian dynamics simulations across the full $(\beta ,\rho )$ plane complete the picture, yielding both the diffusion coefficients and the phase diagram of normal, hopping, and trapped states.

There exist pairs of orthogonal Latin squares of any order $n$ except if $n=2$ or $n=6$ [Bose et al., Further results on the construction of mutually orthogonal latin squares and the falsity of Euler’s conjecture, Can. J. Math. 12, 189 (1960)]. In particular, the problem of Euler’s thirty-six officers does not have a solution. However, it has a “quantum solution”: there exist so-called entangled quantum Latin squares of order 6 [Rather et al., Thirty-six entangled officers of Euler: Quantum solution to a classically impossible problem, Phys. Rev. Lett. 128, 080507 (2022)]. We prove that mutually orthogonal quantum Latin squares of order 6 do not exist if entanglement is not allowed.

Feedback control in open quantum dynamics is crucial for the advancement of various coherent platforms. However, currently only a handful of feedback master equations exist in the literature, which are restricted to specific types of feedback. In this letter we first introduce a unifying framework, based on a single general equation, that describes all possible feedback schemes in sequentially (and continuously) measured systems, and from which all previous results follow. Next, we specialize it to the case of quantum jumps and introduce a new type of feedback based on the channel of the last detected jump, as well as the time elapsed since it occurred. Our description is experimentally grounded, and naturally allows for the introduction of realistic effects, such as time-delays in the feedback loop. We illustrate our results with two time-dependent feedback protocols conditioned on quantum-jump detections: one achieving population inversion of a two-level system against a thermal bath, and another enabling real-time reversal of quantum transitions, both admitting steady-state solutions.

We prove an analog of the “bottleneck theorem,” well-known for classical Markov chains, for Markovian quantum channels. In particular, we show that if two regions (subspaces) of Hilbert space are separated by a region that has very low weight in the channel’s steady state, then states initialized on one side of this barrier will take a long time to relax, putting a lower bound on the mixing time in terms of an appropriately defined “quantum bottleneck ratio.” Importantly, this bottleneck ratio involves not only the probabilities of the relevant subspaces, but also the size of off-diagonal matrix elements between them. For low temperature quantum many-body systems, we use the bottleneck theorem to bound the performance of any quasilocal Gibbs sampler. This leads to a new perspective on thermally stable quantum phases in terms of a decomposition of the Gibbs state into multiple components separated by bottlenecks. As a concrete application, we show rigorously that weakly perturbed commuting projector models with extensive energy barriers (which include certain classical and quantum expander codes) have exponentially large mixing times.

Entanglement has been identified as a key resource for enhancing charging performance in quantum batteries. We show that the kicked-Ising model at the self-dual point provides an explicit charging mechanism, where maximal entanglement growth yields maximal energy injection. Identifying the Floquet dynamics as a Clifford quantum cellular automata and considering exact diagonalization in momentum space, we analytically characterize the charging process, featuring a stable performance while achieving maximal charging. We further propose a fixed time window protocol that accelerates charging toward the continuously driven transverse-field limit. Spin-correlator analysis reveals that scrambling and light-cone spreading govern charging performance. The protocols remain compatible with diverse platforms, underscoring their scalability and practical feasibility.