Papers

We study recoverable entanglement in a four-qubit cluster-state register whose two detector qubits couple to a scalar field. A local preparation phase leaves the initial reference–register entanglement and detector marginal unchanged, but controls protection under collective noise. At the optimal phase, a fixed decoder recovers a Bell pair after any channel preserving the singlet and triplet sectors. For uniformly accelerated detectors at finite separation, an exact trace-norm formula shows that the same phase is optimal at every time within the secular weak-coupling dynamics. Small separation produces a slow decay, whose rate and phase-dependent amplitude we derive. Matching the local response to an inertial thermal bath gives an analytic optimum time for the entanglement contrast. A detector measurement and conditional phase correction recover a two-qubit teleportation resource. Spatial smearing and an ordered weak-coupling then small-separation limit specify the microscopic scope of the lifetime prediction.

We study the transverse-field axial next-nearest-neighbor Ising (ANNNI) model on the square lattice and on a bilayer. At the classical multiphase point $\kappa=J_2/J_0=1/2$, every configuration of straight domain walls that separates domains of at least two sites is a ground state. The walls are rigid, so perturbation theory in the transverse field $g=\Gamma/J_0$ can be carried out for each configuration separately, and we take it to order $g^8$. Quantum fluctuations select $\langle 3\rangle$ ($\uparrow\uparrow\uparrow\downarrow\downarrow\downarrow$) at order $g^2$, because spins next to a wall gain the most energy from virtual flips. The structures $\langle 23\rangle$, $\langle 223\rangle$ and $\langle 2223\rangle$ then open between $\langle 3\rangle$ and the antiphase $\langle 2\rangle$ at orders $g^4$, $g^6$ and $g^8$, in the order of the Fisher-Selke sequence of the classical three-dimensional model. A second layer suppresses each successive phase more strongly, beyond the stiffening of the local fields. We test the two widest phases with stochastic series expansion quantum Monte Carlo, comparing the free energies of the competing ordered states by thermodynamic integration, since annealing freezes in the modulation that forms at the ordering transition. The simulations reproduce the $\langle 3\rangle$ wedge to about 1%, and in a pre-registered test $\langle 23\rangle$ is stable at six of seven points, with the seventh resolved by post-hoc runs.

We study the recently introduced SWAP ensemble for Ising spin-glasses, where the spins obtain varying lengths, with length scale $\Delta \in [0, 2]$. The lengths can be exchanged in the spirit of the SWAP algorithm for glassy poly-disperse hard-sphere systems. Using an annealing schedule, if the annealing is slow enough, ground states of the corresponding Ising Hamiltonian, where the spin lengths are incorporated into the bonds, can be obtained with high probability. We prove this statement for two-dimensional systems with sizes of up to $L^2=1024^2$ spins by comparison with exact ground states obtained by using graph matching algorithms. In particular, we analyze the nature of the obtained realizations of the disorder by calculating exact zero-temperature domain-wall energies, from exact ground state calculations using periodic and anti-periodic boundary conditions. For medium or large values of $\Delta$, e.g. $\Delta=1$, the realizations turn ferromagnetic if the annealing is slow enough, i.e., they lose their zero-temperature spin-glass property. If $\Delta$ is small, the realizations remain glassy, but the SWAP annealing does not easily find a true ground state.

We develop a new model that provides a unified description of the equilibration and subsequent transport of conserved charges, including baryon number, electric charge, and strangeness, as well as the dynamical formation and evolution of the quark-gluon plasma medium in high-energy nuclear collisions. This is achieved by extending the state-of-the-art model of dynamical core-corona initialization to incorporate phenomenological source terms for conserved charges within a full (3+1)-dimensional hydrodynamic framework; the updated model is referred to as DCCI3. Consequently, the model simultaneously describes the core (equilibrium) and corona (nonequilibrium), including their mutual interactions. We present a detailed construction of the DCCI3 model and employ it in numerical simulations of Pb+Pb collisions at $\sqrt{s_{NN}}=2.76~\mathrm{TeV}$ to investigate the resulting dynamics of matter and conserved charges, with particular emphasis on the longitudinal structure. We find that each of the chemical potentials exhibits sizable fluctuations around midrapidity, which challenges the conventional assumption of vanishing values as an oversimplification. Moreover, the baryon chemical potential increases sharply with rapidity and becomes comparable to the temperature at forward rapidities. This suggests that the Rapidity Scan (RS) approach in high-energy nuclear collisions can serve as a complementary probe to the Beam Energy Scan (BES) in exploring the QCD phase diagram.

Process tensors in matrix product operator representation (PT-MPOs) are a powerful tool to calculate the temporal evolution and multi-time correlations of open quantum systems. While much progress has been made in making the calculation of process tensors for larger system dimensions possible, the numerical cost of the subsequent propagation of the system typically scales as $\mathcal{O}(d^6)$, which renders PT-MPO methods prohibitively expensive for system dimensions above several dozens. Here, we show how PT-MPO methods can be used efficiently when only some of the system states couple to the environment, and how combination with a Taylor expansion method allows for a reduction of the numerical complexity down to $\mathcal{O}(d^3)$. We show that these methods enable efficient simulations of systems with several hundreds of states. This is particularly relevant for solid-state cavity-QED systems with multiple modes, or when calculating frequency-filtered correlation functions by coupling sensor systems to the system of interest.

By applying the Iyer-Wald formalism to the modified Lagrangian form for the gravitational system, where the coupling constants appearing in the original Lagrangian form, such as the cosmological constant, are promoted to the dynamical scalar fields by introducing the corresponding auxiliary gauge fields, we derive the first law of the extended black hole thermodynamics, where the resulting thermodynamic volumes as the conjugate thermodynamic variables to the coupling constants are nevertheless independent of the auxiliary gauge fields and exactly the same as those obtained before via varying the coupling constants by brute force. In addition, it is further shown that such volumes can also be expressed in terms of the auxiliary gauge fields and evaluated on the black hole horizon, validating the proposal made in the previous literature.

Metasurfaces are ultrathin optical elements that control light through carefully engineered structures smaller than the wavelength of light, enabling compact devices with functionalities that are difficult to achieve with conventional optics. However, exploiting their full design freedom over large areas has been prohibited by the large computational cost of repeated electromagnetic simulations required for inverse design. Here we introduce a physics-tailored deep-learning surrogate model that exploits the locality and symmetries of electromagnetic interactions to generalize from small-scale simulations to metasurfaces orders of magnitude larger. The model captures nonlocal interactions while predicting optical fields more than four orders of magnitude faster than the conventional electromagnetic solver it is trained on, enabling gradient-based topology optimization under arbitrary illumination. We validate the approach through the inverse design and experimental realization of free-form metagratings with diffraction angles up to 75 degrees, as well as a millimeter-scale free-form holographic metasurface more than 1,000 wavelengths across and comprising 1.6 billion degrees of freedom. By decoupling the scale of electromagnetic simulation from the scale of inverse design, our approach enables system-scale free-form photonic devices that retain nanoscale design freedom.

Establishing a complete set of gates across spatially separated quantum nodes is fundamental for distributed quantum computation and communication networks. One of the approaches to do so consists of employing a superconducting device as a universal quantum node that is capable of storing and processing quantum information, and traveling microwave photons as means of communication. In this work, we realize an entangling gate across a primitive two-node superconducting circuit QED network consisting of two dilution cryostats, A and B, connected via a 30-m-long cryogenic quantum link. We perform a bidirectional photon transfer protocol, where a microwave photon emitted by the communication qubit at A acquires a conditional phase based on the state of qubit B. We vary the communication photon frequency, hence tuning the conditional phase acquired during the reflection off the remote node, effectively implementing an arbitrary-phase CZ gate. We use this entangling operation to perform single-shot readout of the qubit in node B from node A. An interesting feature of our scheme is that it does not require precise synchronization of the active node with the remote node; in particular, remote readout can be performed without any active participation by the remote node. These protocols add to the quantum communication toolbox with superconducting circuits and provide a way of realizing basic distributed quantum computing operations.

Full-wave electromagnetic (EM) simulation enables accurate patch-antenna analysis but is computationally expensive for large-scale forward prediction and inverse design. We present a mesh-native, physics-augmented graph-learning framework that treats radiation-pattern prediction as signal reconstruction on an irregular surface mesh. For the forward problem, a GPS graph transformer is trained with Physics-Augmented Intermediate Supervision (PAIS), an auxiliary node-level objective that predicts complex surface currents, the physical intermediate linking geometry to radiation. PAIS improves multiple GNN backbones at no inference-time cost, while shuffled-current and non-physical controls show the gain comes from physical correspondence. Direction-conditioned decoding and a differentiable radiation-integral consistency loss further exploit this structure. On an 80,000-sample CST benchmark, GPS+PAIS reaches MSE 0.17 / PSNR 19.67, generalizes to a PCA split, and transfers zero-shot to canonical patches. For inverse design, surrogate-filtered diffusion beats nearest-neighbor retrieval by 32% relative MSE.

The growing demand for large-scale database search in data-intensive applications, ranging from proteomics to autonomous systems, has exposed fundamental limitations in von Neumann architectures due to memory bandwidth and energy constraints. Hyperdimensional (HD) computing offers a robust and parallelizable framework for such tasks, but its practical implementation remains challenged by high memory demands. Ultra-high-density, energy-efficient ferroelectric NAND (FE-NAND) memory provides a potential solution by enabling in-situ computation. We fabricate quad-level FE-NAND strings with wide memory windows, disturb resilience, and robust retention. Using these planar FE-NAND strings as building blocks, we experimentally demonstrate in-situ multi-level cell (MLC) dot product operations at the single-cell level and, using experimentally calibrated physics-based simulations, demonstrate Hamming similarity calculations between reference and query hypervectors (HV). This platform leverages the inherent error tolerance of HD computing to achieve >90% search accuracy even at high logic levels (TLC, QLC). When benchmarked on Open Modification Search (OMS) tasks in proteomics with TB-scale datasets, our system shows nearly 1,000x speedup and over 10,000x energy efficiency improvement compared to incumbent solutions. These results establish FE-NAND as a viable in-storage compute architecture for large-scale, high-dimensional data processing.

Quantum algorithms enable Heisenberg-limited scaling across many tasks in sensing and learning, achieving precision $\varepsilon$ using $O(1/\varepsilon)$ total evolution time. However, in Hamiltonian property testing, the best known algorithms have $O(1/\varepsilon^2)$ total evolution time, unless it is possible to $\textit{reverse}$ the flow of time under the Hamiltonian. In this work, we prove that time reversal is necessary to close this gap. We establish evolution time lower bounds for Hamiltonian certification and locality testing, for a continuous family of error metrics ranging from average- to worst-case. We also prove matching upper bounds for Hamiltonian certification in all cases, both with and without time reversal, showing that the advantage from time reversal persists. Our results follow from a new Fourier-analytic approach to quantum lower bounds in continuous time, which is sensitive to time reversal and applicable beyond Hamiltonian property testing. This gives an alternative proof that inverses are required for amplitude amplification and estimation, improving the lower bounds of Tang and Wright and extending to fractional queries. We also show that, for unstructured search, uncertainty in the phase of the oracle destroys the quantum speedup without inverse queries, even when the oracle is fixed and coherent. Our work rigorously establishes time reversal as a resource governing both the precision of quantum measurement and the robustness of quantum algorithms.

We propose a protocol for the remote implementation of an arbitrary two-qubit unitary operation using pre-shared entanglement. In our protocol, Bob possesses an unknown two-qubit state, while Alice implements the required operations using calibrated black-box devices. Alice does not need to know the parameters of these operations, and Bob's unknown state never leaves his laboratory. The protocol is based on the Euler decomposition of single-qubit unitary operations and the Cartan decomposition of two-qubit unitary operations. First, we construct protocols for the remote implementation of the single-qubit operation $U = R_z(\gamma)R_x(\beta)R_z(\alpha)$ using pre-shared Bell states. We then construct a protocol for the two-qubit operation $R_{zz}(\theta)$ using a single pre-shared Bell state and extend it to $R_{xx}(\theta)$ and $R_{yy}(\theta)$ through local unitary transformations. These elementary protocols are finally combined to implement an arbitrary two-qubit unitary operation. A third party, Charlie, determines the required decomposition and provides Alice with the corresponding black-box devices before the protocol begins. Thus, neither Alice nor Bob requires the classical description of the unitary operation.

Estimating the volume of a high-dimensional convex body is a fundamental problem in theoretical computer science. Given a quantum membership oracle for a convex body $K\subset\mathbb{R}^d$, we show that estimating $\mathrm{vol}(K)$ to relative error $\varepsilon$ takes $\widetilde O(d^{5/2}+d^{3/2}/\varepsilon)$ queries. This improves the previous quantum upper bound $\widetilde O(d^3+d^{9/4}/\varepsilon)$ of Chakrabarti et al. (ACM TQC 2023) and Cornelissen–Hamoudi (SODA 2023), and achieves a larger quantum speedup over the currently best classical upper bound $\widetilde O(d^{7/2}+d^3/\varepsilon^2)$ of Jia et al. (JACM 2026). Our quantum algorithm combines two new ingredients: an input-dependent effective spectral-gap analysis of quantum walks based on uniform classical warm-start mixing bounds, and a single quantum estimator for products of normalizer ratios in simulated annealing based on classical bridge sampling. We also prove an $\Omega(d)$ quantum query lower bound for constant relative error, improving the previous $\Omega(\sqrt d)$ lower bound.

Disintegrating rocky planets provide a rare opportunity to probe material escaping directly from intensely irradiated planetary surfaces. We present time-resolved, low-resolution ($R\simeq600$) optical spectroscopy and complementary ground-based photometry of BD+05 4868 Ab. The in-transit spectra exhibit an additional unresolved absorption feature near the O I triplet at 7771.94, 7774.17, and 7775.39 Angstroms relative to the out-of-transit baseline. The feature has an equivalent width of $W_\lambda\simeq1.4\pm0.2$ Angstroms, a maximum differential depth of approximately 9%, and an apparent width of 13-16 Angstroms, comparable to the instrumental resolution. We interpret the feature as candidate O I absorption from an oxygen-bearing mineral-vapor outflow. The $3s\,{}^5S^\circ_2$ lower level of the triplet lies 9.146 eV above the ground state and cannot be appreciably populated in LTE at the reported planetary temperature, requiring non-LTE excitation. A one-zone forward model in which photoionization, O$^+$ recombination, radiative cascade, and radiative trapping populate the excited state reproduces the measured equivalent width and instrumentally broadened line profile. The model favors an atomic component with a projected extent larger than the narrow condensed-dust layer and permits gas-to-dust mass-loss ratios of order a few for representative ionizing irradiation. Stellar O I line-profile variations remain the principal alternative at the present spectral resolution. We therefore identify escaping O I as the preferred physical interpretation while retaining the designation candidate O I. High-resolution, phase-resolved spectroscopy can directly test this interpretation by resolving the individual triplet components.

Nonlinearity can induce topological phase transitions in periodic systems. It is hence of considerable interest to examine if such transitions persist in the absence of translational symmetry. We address this question directly in real space, using the periodic Su-Schrieffer-Heeger (SSH) chain as a reference for understanding the effect of quasiperiodicity. How nonlinearity drives a chain towards a topological phase transition is found to depend strongly on the strength of the quasiperiodic potential. As the nonlinearity strength increases, we find that weak quasiperiodicity supports a transition from a trivial to a topological phase, whereas the intermediate regime does not have a topological phase transition. Under strong quasiperiodicity, pronounced boundary localization can develop well before a nonlinearity-induced topological transition. Our results show how nonlinearity may interplay with a quasiperiodic potential in inducing topological phase transitions and that boundary localization of nonlinear eigenstates alone may not be taken as a clear signature of topological edge states.

We propose a spin-density-matrix framework for probing anomalous $Wtb$ interactions in top-quark pair production by exploiting the polarizations of the $b$ quark and the $W$ boson and their spin correlations. The $b$-quark spin is analyzed through angular distributions in semileptonic $\Lambda_b$ decay following fragmentation, while the leptonic $W$ decay serves as a $W$-polarization analyzer. We derive the $bW$ spin density matrix in the presence of anomalous $Wtb$ couplings and show that its polarization and spin-correlation parameters provide linear sensitivity to these couplings. We construct experimentally accessible angular observables associated with these parameters and evaluate their statistical sensitivities. For the HL-LHC at $\sqrt{s}=14~ \mathrm{TeV}$ with an integrated luminosity of $3000~ \mathrm{fb}^{-1}$, the proposed method yields improved constraints on most anomalous $W t b$ couplings, with the sensitivity to $V_R$ enhanced by a factor of 8 and that to $g_L$ by a factor of about 6.

Optimization in machine learning is usually expressed through iterative rules that update model parameters using information from the loss landscape. In this work, we study an alternative viewpoint in which parameter optimization is treated as the evolution of a dissipative dynamical system. The model parameters are regarded as generalized coordinates, the loss acts as a potential energy, and a positive-definite metric defines the local kinetic geometry of parameter space. Starting from a variational formulation, we derive the corresponding Hamiltonian dynamics, the geometric force generated by a position-dependent metric, and a metric-compatible Rayleigh dissipation law. The resulting continuous system satisfies a monotonic energy-dissipation relation, while its discrete form allows the influence of curvature on the optimization trajectory to be studied directly. We illustrate the framework using a controlled CIFAR-10 image-reconstruction problem for which the optimum is known analytically. With the image Hessian used as the metric, the curvature dependence of the quadratic modal dynamics is removed. We then reparameterize the same image as a matrix product state, producing a genuinely position-dependent metric and a nonzero geometric force. Poincaré return maps provide a complementary phase-space view of the resulting contraction dynamics. These examples establish HAMLET as a geometric, energy-based framework for studying optimization as dissipative motion in parameter space. On a five-seed MNIST MLP benchmark, HAMLET attains the highest mean test accuracy (97.95%) and the lowest mean test negative log-likelihood (0.0696) among the three evaluated optimizers.

We develop an equivariant K-theoretic vertex formalism for a colored, abelianized higher-rank sector on smooth projective toric threefolds $X$. Nonzero first Chern classes are encoded as magnetic fluxes and absorbed into line-bundle twists, after which the virtual character is redistributed into finite perturbative, vertex, and edge contributions. We compute the resulting (unreduced and trace-free) virtual dimensions and analyze the interaction terms relevant to a possible reduction to rank one. We emphasize that, on a compact toric threefold, colored partitions do not classify all torus-fixed stable higher-rank sheaves: the resulting series is therefore a proposed abelianized/framed vertex series unless an additional comparison theorem with the full stable-sheaf moduli problem is supplied. When the threefold obstruction theory is not available in the desired form, we pass to the local Calabi–Yau fourfold $Y=\operatorname{Tot}(K_X)$ and formulate the corresponding colored DT4 vertex. A $K_X$-twisted tautological insertion removes fixed points with nontrivial fiber layers, reducing solid partitions to plane partitions at the level of the local vertex. In rank one we give a scheme-theoretic explanation: the Hilbert functor of subschemes of $X$ is canonically isomorphic to the constrained Hilbert functor of subschemes of $Y$ lying scheme-theoretically in the fixed zero section. Under the hypotheses of the DT4 K-theoretic Lefschetz/virtual-pullback formalism, the associated support insertion reduces the rank-one fourfold theory to the threefold theory. We keep this global rank-one statement logically distinct from the higher-rank colored-vertex reduction.

We investigate the effective action of a 7-dimensional topological $BF$ theory under a 4-dimensional reduction. We discuss the topological implications of the resulting theory and analyze the corresponding field equations. In particular, we derive exact solutions to these equations of motion in both Minkowski and Schwarzschild spacetimes.

We study anomaly-induced semiclassical backreaction on an analytic family of discretely self-similar solutions of Einstein–Klein–Gordon theory at large spacetime dimension. Horizon regularity fixes a null-coordinate Floquet exponent and selects a unique regular quantum state. The Polyakov auxiliary field is affine-periodic rather than periodic, with a monodromy that is determined independently by a global zero-mode condition and by the conformal-coordinate scaling. Spherical reduction introduces a quantum coupling that grows toward the center, so the periodic first-order expansion is nonuniform. We construct the resulting nonlinear inner problem and find a critical dilaton surface. Generic crossings of this surface are singular, whereas matching to the regular zero-mass exterior selects a narrow, high-curvature throat. The anomaly also separates the effective null-energy boundaries from the classical matter flux and zero-curvature curves. These results show that the minimally coupled Polyakov model does not yield a generic smooth, exactly self-similar completion of the classical center.

Floquet dressing offers a route to controlling electronic states through periodic optical driving. Its realization in solids has centred primarily on topological-insulator surface states, semiconductors and two-dimensional Dirac semimetals. Extending this control to bulk metals would enable manipulation of the itinerant states underlying metallic transport and collective order. Yet strong screening and rapid scattering have long cast doubt on its feasibility in bulk metals, while photoelectron dressing complicates its identification. Here we identify Floquet dressing of the overlapping, bulk-derived metallic bands of 2H-NbSe2 using time- and angle-resolved photoemission spectroscopy. Photon-shifted replicas in a sparse unoccupied-state window retain the parent-band dispersions and appear only during pump–probe overlap. Rotating the pump's linear polarization at fixed probe polarization redistributes replica weight between momentum-space branches. With a common parameter set, a model accounting for the optical fields inside and outside the solid captures this redistribution through coherent Floquet–Volkov interference more closely than either pathway alone or their incoherent intensity sum. These findings extend Floquet dressing to the itinerant bulk bands of a multiband metal without relying on the observation of energy gaps opened by hybridization between parent bands and their photon-dressed replicas, providing a basis for exploring how coherent optical dressing couples to metallic transport and collective electronic phases.

As a continuation of our previous work, with the grand desert hypothesis, we prove that we can probe the Supersymmetric Grand Unified Theories (GUTs) with gauge meidation at the future proton-proton collider and Hyper-Kamiokande experiment. For the GUT scale $M_{\rm GUT}$ less than or equal to $0.84\times10^{16}$~GeV, the proton lifetime for dimension-six proton decay via heavy gauge boson exchange is less than or around $5\times10^{34}$ years, and thus we can probe it at the Hyper-Kamiokande experiment. For $ M_{\rm GUT} \ge 0.84 \times 10^{16}$ GeV, the lightest neutralino is the Next to the Lightest Supersymmetric Particle (NLSP), as well as the upper mass bounds on the gluino and first two generation squarks are 8.64 TeV and 11.82 TeV, respectively. Therefore, the gluino and first two generation squarks can be probed at the future 100 TeV proton-proton collider such as ${\rm FCC}_{\rm hh}$ and SppC. Moreover, we discuss the mass spectra for the colored sparticles, sleptons, pseudo-scalar Higgs and electroweakinos. If the sparticles were discovered, it might give us hint on the messenger scale, the effective supersymmetry breaking scale, and the renormalization group evolution of the supersymmetry breaking soft terms.

The quantum PCP conjecture is one of the major open problems in quantum complexity theory. It has resisted attack in part because many primitives used in the proof of the classical PCP theorem, such as locality-preserving gap amplification and alphabet reduction, have no obvious quantum analogues due to quantum no-cloning. Locality-preserving gap amplification is a procedure that takes as input a local Hamiltonian problem instance and produces a new instance with a larger promise gap, without increasing the locality of the Hamiltonian, and instead moderately increasing its local qudit dimension. Obtaining this kind of control over the locality during gap amplification is critical to the success of many known strategies for proving the classical PCP theorem. In this work, we put forth the first known viable template for quantum locality-preserving gap amplification, and we prove that our procedure amplifies the combinatorial gap of local Hamiltonians. Our work introduces a new framework for reasoning about quantum gap amplification in terms of fault-tolerant computation, and illuminates a route toward importing one of the central ingredients in classical PCPs into the quantum setting. In particular, we build upon ideas from the recent classical PCP of Bafna–Minzer–Vyas based on high-dimensional expanders, and the circuit-to-Hamiltonian construction of Anshu–Breuckmann–Nguyen, in addition to several recent advances in quantum coding theory.

Traditional theories of electrolyte and polyelectrolyte solutions overlook ion and polymer hydration, yielding an overly idealized perspective of the thermodynamic and dynamic properties of these solutions. In particular, the propensity of certain ions to increase or decrease the water diffusion coefficient at low solution concentrations, is poorly understood, a phenomenon that correlates strongly with the Hofmeister series describing the influence of salts on the solubility and self-assembly of synthetic and biomacromolecules as well as colloidal particles. These ion-specific effects have profound ramifications in diverse biological, medical science and technological applications. We address the general problem of understanding ion and uncharged water-soluble polymer hydration through molecular dynamics (MD) simulations of representative water-soluble polymers, polyacrylamide (PAM) and polyethylene oxide (PEO), in aqueous salt solutions. Careful attention is given to the capacity of our model to reproduce observed trends of added monovalent salts on the diffusion coefficient of water. Reproducing these ion-specific trends in the mobility of water has been a recurrent challenge in prior MD simulations of aqueous solutions based on a physically realistic model of water. Our work on salt solutions represents an important advance on which we build our modeling of aqueous polymer solutions with added salts. Simulations of our model polymers reveal an extended nanoscale dynamic hydration layer having a scale on the order of one nanometer (nm) in which the mobility is perturbed from its bulk value, and the mobility gradient in this layer appears to obey a near universal functional form.

The competitive interactions arising from the proximity of positive and negatively charged groups in the monomers in polyzwitterions (PZ) makes these polymers have properties similar in some ways to intrinsically disordered proteins. To gain qualitative insights into this important class of water-soluble polymers, we performed molecular dynamics (MD) simulations of a model PZ chain with an explicit solvent to understand the conformational state in the absence and presence of added salt. We find that isolated PZ chains under salt-free conditions adopt a self-associated state having a weak dependence on temperature. The addition of an appreciable amount of NaCl leads to a weakening of the intrachain associations, resulting in chain expansion, a transition reminiscent of the denaturation of globular proteins. In particular, the hydrodynamic penetration function, the ratio of hydrodynamic radius to the radius of gyration, of the PZ chains under salt free conditions, is found to be more consistent with a randomly branched polymer or single chain nanoparticle than a random coil polymer where the physical cross-links within the chain arise from the dipoles within the chain. The chain conformation not only tends to become larger with the addition of salt but also acquires a more appreciable temperature dependence of its average size with temperature. This swelling trend of PZ molecules with added salt, sometimes referred to as the anti-polyelectrolyte effect, is distinct from the normal trend polyelectrolytes, which typically become more contracted with the addition of salt. We also examined the spatial extent of the dynamic hydration layer the PZ chain, both with and without added salt, and the effect of temperature and salt concentration on the water mobility within this layer, and PZ side-chain mobility, whose dynamics is apparently strongly coupled to the surrounding water molecules.

Basis-independent coherence of a quantum multistate is fixed by whether its constituent states commute, and for qubits it is detected by pairwise state overlaps alone. What governs its deterministic transformation has been open. We give the exact resource-conversion theory of quantum multistates under common commutativity-preserving operations (CPOs). For qubits, pairwise Bargmann invariants determine the singular values of the unique candidate channel, while a single third-order Bargmann phase determines its orientation. Complete positivity then yields a necessary and sufficient criterion for exact conversion. The criterion identifies a chirality-sensitive shell $\mathcal C_{\rm chir}$, within which targets with identical pairwise geometry can differ in convertibility solely by the sign of their cubic invariant. This yields an order separation, $k_{\rm detect}=2<3=k_{\rm convert}$, for qubit multistates of every size $n\geqslant3$. The chirality-sensitive shell occupies exactly one third of the singular-value simplex, while mirror reflection obstructs two thirds of the admissible orientation-preserving transformations by volume. For $d\geqslant3$, by contrast, the structure is rigid: every resourceful conversion is realized by either an isotropic depolarizing or a transpose-depolarizing channel. Convertibility is then decided by centered Bargmann invariants of degree at most $d^2$.

The interstellar comet 3I/ATLAS exhibits unusual polarimetric properties compared with Solar System comets, while constraints on its fundamental physical properties, such as dust albedo and grain-size distribution, remain limited. We obtained new optical polarimetry near opposition with the Pirka Telescope, combined it with previously reported polarimetric measurements, and constructed a visible-to-mid-infrared spectral energy distribution (SED) from HST, VLT, SPHEREx, and JWST observations. The SED indicates that the coma is dominated by dark, absorbing dust, with an effective V-band albedo of $p_{\rm eff}\sim0.04$. Modeling the SED with a power-law grain-size distribution yields a size index of $q=3.0$–$3.3$. The mid-infrared spectral structure is better reproduced by adding a minor amorphous-silicate component. The combined polarimetric data further favor a highly porous scattering structure. Despite its unusual polarimetric behavior, the dust of 3I/ATLAS has an albedo and grain-size distribution within the range found for Solar System comets.

Swampland principles, combined with the smallness of dark energy $\Lambda$, lead to the dark dimension scenario, with one extra dimension of micron size. We review this scenario and its predictions: KK graviton dark matter (or the KK tower of the quintessence field into which the gravitons convert), neutrino masses tied to $\Lambda^{1/4}$ via a bulk $B-L$ gauge symmetry, QCD axion decay constant $f_a\sim \Lambda^{1/12}\sim 10^9-10^{10}$ GeV at the 5d Planck scale $M_5$, connecting electroweak hierarchy to $\Lambda^{1/6}$, and a relation between the GUT and weak scales with $M_5$ as the geometric mean. The dark dimension also provides a concrete realization of an evolving dark sector: the evolution of its diameter correlates the variation of dark energy with that of the dark matter mass, fitting the recent DESI DR2 (+CMB+supernovae) data while avoiding the phantom crossing that the $w_0w_a$CDM parametrization would suggest—the apparent phantom behavior instead arises from the evolving dark matter mass. The fits suggest that the dark energy field sits in the interior of moduli space, near an unstable critical point. Motivated by this, we review recent progress on non-supersymmetric string vacua: isolated critical points protected by duality symmetries, in non-geometric flux compactifications and in Scherk–Schwarz compactifications of M-theory, and an emerging duality web for non-supersymmetric strings. This note is based on two talks given by the author at String Phenomenology 2026 (Paris) and Strings 2026 (Shanghai).

Inequality constraints in combinatorial optimization are conventionally handled by introducing slack variables and quadratic penalties, which increase the qubit count and distort the optimization landscape. Slack-free formulations instead apply a nonlinear custom penalty function directly to the constraint, which are difficult to be implemented in quantum approximate optimization algorithm (QAOA). We show that the Walsh–Hadamard transform (WHT) removes this obstruction for any penalty function: a penalty applied to a linear constraint is exactly a weighted sum of Pauli-$Z$ strings. We propose this framework as the Walsh custom penalty QAOA (WCP-QAOA). Truncating the expansion at Walsh degree $k$ costs $\mathcal{O}(n^k)$ Pauli terms and leaves the qubit count untouched. The truncation is the optimal degree-$k$ approximation of the penalty in $L^2$, and we give a condition on the discarded Walsh coefficients under which the truncated Hamiltonian still ranks every feasible solution below every infeasible one. Since evaluating a Walsh coefficient from its definition requires all $2^n$ penalty values, we give an algorithm that returns any coefficient in sub-exponential time, so that the degree-$k$ Hamiltonian is obtained in time polynomial in $n$ for fixed $k$. We show that for the exponential penalty, there exists a closed product form of WHT, and hence a closed form expression to calculate the Walsh coefficients. We identify structural shortcuts that shorten the exact spectrum. We also tested WCP-QAOA in solving a 6-qubit knapsack problem.

TbMn6Sn6 is a centrosymmetric ferrimagnetic kagome metal that combines topological electronic states with strong magnetic anisotropy and a near-room-temperature spin-reorientation transition (SRT). Real-space imaging studies of thin specimens have revealed helical stripes, biskyrmion-like textures, and skyrmion-bubble-like structures in the spin-reorientation regime. Whether such local textures develop into a bulk long-range-ordered skyrmion lattice remains unresolved. Here we present small-angle neutron scattering (SANS) results probing the mesoscale magnetism of a bulk TbMn6Sn6 single crystal. We observe no sixfold SANS Bragg pattern indicative of a long-range-ordered skyrmion lattice under the explored conditions. Instead, the dominant magnetic response is an anisotropic twofold low-Q scattering component whose intensity distribution and field dependence evolve markedly across the spin-reorientation regime. In zero field, a broad and horizontally elongated low-Q signal develops above TSR and weakens as the system approaches the paramagnetic state. At 345 K with H || b, the signal is diffuse and is suppressed rapidly below about 700 Oe. By contrast, at 310 K with H || c, close to TSR, the response is more concentrated and line-shaped and persists to higher fields. The contrasts between these scans likely reflect the combined effects of rapidly evolving magnetic anisotropy near TSR and the field geometry. Our results therefore establish a bulk anisotropic mesoscale magnetic response across the spin-reorientation regime, consistent with stripe- or domain-related textures reported by real-space imaging, while not uniquely identifying their real-space morphology.