Quantum reflection is usually described as an effectively one-dimensional phenomenon governed by motion along the surface normal. However, when translational symmetry is broken by sharp geometric features, scattering becomes intrinsically multidimensional. Here, we show that singular corners generate new geometric scaling laws for quantum reflection. In a minimal two-dimensional corner model with an attractive quadrant interaction, the reflected scattering width scales as ${\sigma }_{\mathrm{refl}}\propto E^{-2}$ in the intermediate Born regime, followed at lower energies by a crossover to the unitarity-limited threshold law ${\sigma }_{\mathrm{refl}}\propto E^{-1/2}$. The $E^{-2}$ exponent arises from two geometric ingredients: half-space support of the interaction and specular boundary-layer kinematics. More generally, for corner-supported potentials of the form $V(x,z)=W(x,z)\mathrm{\Theta }\left(x\right)\mathrm{\Theta }\left(z\right)$, we show that the Born exponent is universal under mild regularity assumptions. The leading coefficient is asymptotically determined by a specular boundary layer and depends only on the boundary trace $W(x,0)$, while microscopic details away from the boundary enter only through subleading structure. These results identify corners as the simplest surface singularities that support genuinely multidimensional geometric scaling laws, showing that geometry alone can control reflection across different energy regimes beyond the standard one-dimensional framework.

Ising machines, which are dynamical systems designed to operate in a parallel and iterative manner, have emerged as a paradigm for solving combinatorial optimization problems. Despite computational advantages, the quality of solutions depends heavily on the form of dynamics and tuning of parameters, which are, in general, set heuristically due to the lack of systematic insights. Here, we focus on optimal Ising machine design by analyzing phase diagrams of spin distributions in the Sherrington-Kirkpatrick model. We find that the ground state can be achieved in the phase where the spin distribution becomes binary, and optimal solutions are produced where the binary phase and gapless phase coexist. Our analysis shows that such coexistence phase region can be expanded by carefully placing a digitization operation, giving rise to a family of superior Ising machines, as illustrated by the proposed algorithm digCIM.

We show that a Bose-Hubbard model with local loss exhibits a first-order dark-state phase transition between a dark soliton and a uniform superfluid. Semiclassical simulations and stability analysis reveal that the soliton acts as a many-body dark state, whose suppressed fluctuations modify the transition relative to the comparable phenomenon of optical bistability in Kerr resonators. This mechanism quantitatively captures the bistable phase boundary observed in the experiment of Labouvie et al. [Phys. Rev. Lett. 116, 235302 (2016)], resolving long-standing discrepancies in previous theoretical modeling. Our results identify a general route by which spatial coherence and engineered loss can generate nonequilibrium phase transitions in ultracold gases.

We present a scheme to detect itinerant microwave radiation at the single photon level. Using existing Josephson-photonics devices, where two microwave cavities are coupled by a dc-voltage-biased superconducting junction, we theoretically show how to implement a stroboscopically repeated, near-projective measurement of a photon impinging on one of the cavities. Optimizing rate, duration, and strength of the measurement by flux control of the junction and developing a threshold protocol to detect the photon from a homodyne measurement of the radiation output of the other cavity, we achieve highly efficient detection with low dark counts. By cascading the detector with a preamplifier, where a similar two-cavity Josephson-photonics device acts as a photon multiplier, we can further improve the device to reach a detection efficiency of $88.5\%$ with a dark count rate of $\sim {10}^{-4}{\gamma }_a$, set by the resonance width ${\gamma }_a$ of the absorbing cavity. These results for a preamplification factor of 2 suggest that higher preamplification factors may yield near-unity efficiencies.

Time-resolved atom interferometry, as employed in applications such as gravitational-wave detection and searches for ultralight dark matter, requires precise control over systematic effects. In this work, we investigate phase noise arising from shot-to-shot fluctuations in the atoms’ transverse motion in the presence of the wavefront curvature of the interferometer beam, and analyze its dependence on the laser-beam geometry in long-baseline, large-momentum-transfer atom interferometers. We use a semiclassical framework to derive analytical expressions for the effective phase perturbation in position-averaged measurements and validate them using Monte Carlo simulations. Applied to 100 m and 1 km atom gradiometers representative of next-generation experiments, the model shows that configurations maximizing pulse efficiency also amplify curvature-induced phase noise, requiring micron-level control of the atom cloud's center-of-mass position and submicron-per-second control of its center-of-mass velocity to achieve sub-${10}^{-5}$ rad phase stability. Alternative beam geometries can suppress this noise by up to 2 orders of magnitude, but at the cost of reduced pulse efficiency. To address this limitation, we propose a mitigation strategy based on position-resolved phase-shift readout, which empirically learns and corrects the wavefront-induced bias from measurable quantities such as the phase-shift gradient and final cloud position. This approach restores high-sensitivity operation in the maximum-pulse-efficiency configuration without detailed beam characterization, providing a practical route toward next-generation, time-resolved atom interferometers operating at the ${10}^{-5}$ rad noise level.

Electroadhesion conventionally relies on kilovolt potentials to bridge macroscopic gaps in many practical applications. Here, we demonstrate that the governing length scale for strong electroadhesion is not the device-level separation but the nanoscale gap distribution imposed by surface roughness. By combining boundary-element rough-contact modeling with macroscopic friction measurements on oxidized silicon interfaces, we establish a quantitative framework that predicts adhesion pressures approaching 100 MPa at voltages below 30 V. Furthermore, we uncover a strong polarity-dependent asymmetry in adhesion and friction, which we attribute to charge trapping at grain boundaries. Our findings demonstrate that strong, low-voltage electroadhesion is viable and identify mechanisms through which undesired electroadhesion can be suppressed.

Nonlinear integrated optical devices that can realize threshold filtration of signals are in demand in photonics and optical computing. However, a list of requirements exists for such devices to make them practical. Here, to design a thresholder with the desired behavior, we suggest a mechanism that implements the property of resonators to provide extremely sharp (with respect to the wavelength) $\pi$ phase shifts near the critical coupling regime. By combining this feature with a nonlinear switching mechanism, one may obtain highly sensitive devices. Notably, the sharpness of the phase step in the considered case is independent of the quality factor of the resonators and the corresponding width of the resonances in transmittance. Instead, it is defined by the proximity to the critical coupling regime. Balancing near the critical coupling allows one to vary the sensitivity and achieve controllable smearing of the step function. The described effect is quite robust and can be realized for different materials and types of nonlinearity. The possibility of using sharp steps and low-quality resonators simultaneously provides multiple advantages for the resulting device. These include compact size, low manufacturing requirements, high operation speed, and low switching intensities. These sensitive and tunable phase thresholders may have multiple applications in optical computing. Few examples are provided, including a minimally invasive logic gate and a signal intensity classifier. In particular, the considered thresholders are useful in neuromorphic chips since they may act as optical neurons. In this paper, we provide an example of a photonic scheme that represents the behavior of a neuron and discuss its characteristics. Both the amplitude and phase of light are actively used in the scheme to store and update the state of a neuron.

Phase-separating active systems can display phenomenology that is impossible in equilibrium. The binodal densities are not solely determined by a bulk (effective) free energy, but also affected by gradient terms, while capillary waves and Ostwald processes are determined by three distinct interfacial tensions. These and related phenomena were so far explained at continuum level using a top-down minimal theory (Active Model $\mathrm{B}+$). This theory, by Taylor expanding in the scalar order parameter (or density), effectively assumes that phase separation is weak, which is not true across most of the phase diagram. Here, we develop a quantitative account of active phase separation, by introducing the active counterpart of Cahn-Hilliard theory, constructing the density current from all possible terms with up to four spatial derivatives without Taylor expanding in the density. From this $\mathcal{O}\left({\nabla }^4\right)$ theory, we show how to compute binodals and interfacial tensions for arbitrary choices of the five density-dependent “coefficient functions” that specify the theory (replacing the four constant coefficients of Active Model $\mathrm{B}+$). We further show how a well-studied particle model for active phase separation, involving thermal quorum-sensing active particles (tQSAPs), yields a fully specified example of the $\mathcal{O}\left({\nabla }^4\right)$ theory upon coarse-graining. We find that to coarse-grain consistently at $\mathcal{O}\left({\nabla }^4\right)$ requires a systematic procedure, based on multiple-scale analysis, to eliminate fast-evolving orientational moments. Using this, we calculate from microscopic physics all five coefficient functions of the active Cahn-Hilliard theory for tQSAPs. We identify contributions that were missed in previous continuum theories, and show how neglecting them becomes justified only in the limit of large quorum-sensing range parameter $\gamma$. Comparison with particle-based simulations of tQSAPs shows that, both qualitatively and quantitatively, our $\mathcal{O}\left({\nabla }^4\right)$ theory improves on previous continuum models, predicting not only that binodal densities depend on $\gamma$, but also—unexpectedly—that phase boundaries become reentrant at small thermal diffusivity. A further surprising prediction of the wider theory is that in certain regimes of parameter space, bulk phase separation exhibits an instability in which, at $\mathcal{O}\left({\nabla }^4\right)$ level, the interfacial width shrinks to zero. We link this to the runaway effects of active pumping terms that cause positive feedback of a sharpening interface.

Flows with deformable interfaces are commonly controlled by applying external fields or by modifying the boundaries that interact with the fluid; however, realizing such strategies can be demanding or impractical in many settings. Here, we demonstrate that fluids with broken symmetries can self-control their mechanics. We present a continuum model of a viscous fluid with highly deformable interfaces subject to capillary stresses. Our model features odd viscosity, a parity-violating transport coefficient that emerges in chiral fluids. Using direct numerical simulations of two-dimensional two-phase flows, we focus on the impact of an odd droplet on a superhydrophobic surface. We demonstrate that odd viscosity dramatically disrupts conventional symmetric spreading by inducing asymmetric deformations and chiral flow patterns. Our analysis reveals a variety of unconventional dynamic regimes, including leftward and rightward bouncing as well as rolling, depending on the relative strength of the odd viscosity. Overall, this work presents a framework of broad interest to the control of highly deformable liquids and materials with broken symmetries, as well as to droplet dynamics, where it showcases the potential of odd viscosity as a route for controlling interfacial flows and designing functional metamaterials with tailored fluidic properties.

Multimode quantum light has promising applications in many areas of physics, such as quantum communications and quantum computing. However, its multimode nature also makes it challenging to measure its properties. Recently [I. Barakat et al., Optica Quantum 3, 36 (2025)], a technique for the simultaneous measurement of squeezing of multiple broadband modes based on a phase-sensitive amplification approach was experimentally implemented using a setup that effectively corresponds to an SU(1,1) interferometer. Here, we aim to provide a complete theoretical analysis of the modal structure of (generally unbalanced) SU(1,1) interferometers and a detailed theoretical formal derivation of the framework for this technique. Utilizing the joint Schmidt decomposition of the transfer functions, we investigate the shape and phase profiles of the modes of the SU(1,1) interferometer and its components [parametric down-conversion (PDC) sections] for different parametric gain regimes. We discover a complicated interplay between the PDC modes and the modes of the entire interferometer, and analyze it by using their overlap coefficients as a similarity measure. Finally, we develop a rigorous processing method for the aforementioned multimode squeezing measurement technique and discuss necessary approximations to make this method experimentally feasible.

The Kitaev model is an exactly solvable model that exhibits a quantum spin liquid as its ground state. While this model was originally proposed as an $S=1/2$ spin model on a honeycomb lattice, extensions to higher-spin systems have recently attracted attention. In contrast to the $S=1/2$ case, such higher-$S$ models are not exactly solvable and remain poorly understood, particularly for spin excitations at finite temperatures. Here, we focus on the $S=1$ Kitaev model, which has been proposed to host bosonic quasiparticles. We investigate this model using Schwinger boson mean-field theory, where bosonic spinons are introduced as fractional quasiparticles by extending bond operators to address anisotropic spin interactions. We determine the mean-field parameters that realize a quantum spin liquid in both ferromagnetic and antiferromagnetic Kitaev models. Based on this mean-field ansatz, we calculate the dynamical and equal-time spin structure factors. We find that, when one uses the conventional decoupling scheme based on Wick decoupling with respect to spinons to calculate spin correlations, the resultant spin structure factors exhibit a momentum dependence that is not consistent with the sign structure expected from the exchange interaction: They possess a strong spectral weight indicating ferromagnetic (antiferromagnetic) correlations in the antiferromagnetic (ferromagnetic) Kitaev model. To resolve this issue, we propose an alternative scheme for evaluating the spin correlations, which is based on decoupling with respect to the bond operators. We demonstrate that, in our scheme, this discrepancy is removed, and the momentum dependence of the spin structure factors is consistent with the sign of the exchange constant. We also calculate the temperature evolution of the dynamical spin structure factor and find that the continuum observed at zero temperature splits into two distinct structures as the temperature increases, which can be understood in terms of the bandwidth narrowing of spinons. Finally, we clarify the origin of why the two distinct decoupling schemes result in different momentum dependences of the spin structure factors and discuss their relationship to results obtained in previous studies.

Nonequilibrium dynamics of quantum many-body systems is one of the main targets of quantum simulations. This focus—together with rapid advances in quantum-computing hardware—has driven increasing applications in high-energy physics, particularly in lattice gauge theories. However, most existing experimental demonstrations remain restricted to (1+1)-dimensional and/or Abelian gauge theories, such as the Schwinger model and the toric code. It is essential to develop quantum simulations of non-Abelian gauge theories in higher dimensions, addressing realistic problems in high-energy physics. To fill the gap, we demonstrate a quantum simulation of real-time dynamics in a (2+1)-dimensional $q$-deformed $\mathrm{SU}{\left(2\right)}_3$ Yang-Mills theory using a trapped-ion quantum computer. By restricting the irreducible representations of the gauge fields to the integer-spin sector of $\mathrm{SU}{\left(2\right)}_3$, we obtain a simplified yet nontrivial model described by Fibonacci anyons, which preserves the essential non-Abelian fusion structure of the gauge fields. As a demonstration, we simulate the real-time dynamics of this model using quantum circuits that explicitly implement $F$-moves. In our demonstrations, the quantum circuits execute up to 47 sequential $F$-moves. We identify idling errors as the dominant error source, which can be effectively mitigated using dynamical decoupling combined with a parallelized implementation of $F$-moves.

The Green’s function theory of Lymar’ and Rudoi [Theor. Math. Phys. 21, 990 (1974)] is generalized to the case of multiple intra- and intersublattice magnetic interactions in a collinear spin-half antiferromagnet and applied to magnetic excitations in ${\mathrm{Bi}}_2{\mathrm{CuO}}_4$. The spin Hamiltonian includes both the out-of-plane and in-plane symmetric anisotropy terms and the Zeeman term, which describes the interaction with an external magnetic field $B$ applied along the Néel vector. Within the spin-wave approximation, we calculate spin excitation dispersion, antiferromagnetic resonance frequencies, and the critical field $B_c$ of the spin-flop metamagnetic transition. A weak in-plane anisotropy is shown to result in a gap in the acousticlike branch of the excitations. The gap nonlinearly depends on the external field and closes at $B=B_c$. An expression for the Néel temperature in the Tyablikov random phase approximation at zero field is derived. For the parameters derived from the recent inelastic neutron scattering study by Yuan et al. [Phys. Rev. B 103, 134436 (2021)], it gives $T_{\mathrm{N}}\approx 52\mathrm{K}$.

Roughness-insensitive surface magnetization is an intrinsic property of magnetoelectric antiferromagnets and is today understood as a manifestation of bulk magnetoelectric multipoles. Here, we provide an experimental quantification of the crystal-facet-dependent surface magnetization in the archetypical magnetoelectric antiferromagnet ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and show that the data are consistent with a quadrupolar component of the bulk magnetoelectric multipolization. Using quantitative nanoscale magnetometry on lithographically defined rectangular mesas that expose 30 distinct crystallographic facets, we quantify mesa stray magnetic fields, which arise from differences between the mesa top and side-facet magnetizations. The resulting dataset supports a linear map from surface normal to surface magnetization, from which we directly infer the bulk quadrupolar component within the multipolization framework. Our work provides systematic, facet-resolved evidence of roughness-insensitive surface magnetization, including in-plane components, and delivers a quantitative route to constraining bulk multipoles from surface stray-field data. Beyond addressing the modern theory of magnetoelectric multipolization, our approach offers a generally applicable method to quantify surface magnetizations in antiferromagnetic compounds and informs the choice of crystal cuts for future spintronics devices.

It is known that the opening or closing mechanism of a voltage-gated ion channel is triggered by the potential difference across the cell membrane in the nervous system. Based on this picture, we model the ion channel as a nanoscale two-terminal ionic tunneling junction. We apply an external time-varying voltage on the junction to mimic the membrane potential difference in the stimulation of neurons. We derive the non-Markovian quantum Langevin equation from the first principle of quantum mechanics for the ion transport in ion channels, and obtain the ion transport current in terms of quantum tunnelings of ions controlled by the time-varying voltage. We find that the time-varying voltage induces an effective magnetic flux, which causes quantum coherence in ion tunnelings. This effective magnetic flux induces further an oscillatory component to the spectral structure of the ion system, forming a time-dependent quantum memory. Such voltage-induced memory is defined as the active quantum memory, which manifests in the system with a regular oscillatory sideband structure in the ion transport current. The sideband structure demonstrates a multicrossing hysteresis in the current-voltage $(I-V)$ curve, responding to the variation of the time-varying voltage (membrane potential difference). We also find that the strength of active quantum memory can be described by the ratio of amplitude and frequency of the time-varying voltage, and can be quantitatively measured through the number of nonzero cross points in the $I-V$ hysteresis and conductance-voltage diagram. Additionally, we explore the temperature dependence of the active quantum memory in such a system. Further, we apply this model to the ion channel system on the biological energy scale. The description of these active quantum memory characteristics provides a quantum mechanical understanding to the underlying mechanism of ion channel dynamics.

Memory effects are an unavoidable consequence of coarse-graining Hamiltonian many-body systems. Although Markovian embeddings with auxiliary variables are widely used to approximate such dynamics, their consistency with the exact projected microscopic evolution is rarely examined. Here, we analyze this consistency problem at the structural level. Starting from a general Markovian Fokker-Planck equation defined on an extended state space comprising coarse-grained variables and auxiliary degrees of freedom, we derive the exact non-Markovian evolution governing the marginal probability of the coarse-grained variables. We then identify the conditions under which this marginal equation reproduces the structural form of the generalized Fokker-Planck equation obtained from Zwanzig's projection formalism. These conditions follow from microscopic Hamiltonian dynamics and constrain the admissible form of Markovian embeddings, ensuring consistency with equilibrium structure, conservation laws, positivity, and microscopic reversibility. The resulting framework provides a systematic route for constructing microscopically consistent Markovian representations of non-Markovian coarse-grained dynamics. We illustrate the approach in coarse-grained particle models, ranging from isothermal dynamics to fully energy-conserving nonisothermal formulations.

Non-Hermitian topological matter provides a platform for engineering phenomena that go beyond the capabilities of Hermitian systems, enabling the use of losses to engineer topological phenomena. Non-Hermitian models often rely on artificial platforms made of engineered lattices because controlling losses in natural compounds is challenging. Although typical models for non-Hermitian photonic matter are often single mode, photonic systems are often multimodal, producing mixing between different normal modes in each site. Here, we explore a family of multimodal non-Hermitian lattices, featuring multiple resonant modes. We show that these multimodal models are capable of featuring topological modes and criticality, similar to the artificial single-mode models often considered. We analyze the robustness of these non-Hermitian topological modes to fluctuation of local losses, disorder, and artificial gauge field. We show that these effects can be captured via both a full microscopic model and effective multiorbital models. Specifically, we show that due to their multiorbital nature, the localization properties of non-Hermitian multiorbital models can be controlled by an external gauge field. Our results demonstrate that internal orbital degrees of freedom provide a promising strategy to engineer controllable non-Hermitian topology and criticality.