Fock-state lattice (FSL) offers a powerful quantum simulator for topological phenomena due to the unbounded scalability and ease of implementation. Nevertheless, the unique topological properties induced by its site-dependent coupling have remained elusive, mainly due to the challenge of handling an infinite state space without translational symmetry. Here, we rigorously analyze the topological features of a semi-infinite FSL-based Su-Schrieffer-Heeger (SSH) model, in both Hermitian and non-Hermitian realms, by mapping it to the solvable Jaynes-Cummings model via a unitary displacement transformation. We find a topological zero mode persisting across all parameter regimes, which is more stable than the conventional SSH model. It originates from the bound state at the inherent domain wall under anisotropic conditions. With gain and loss introduced, we predict a non-Hermitian bound effect, i.e., any state overlapping with the bound state will quickly stabilize to the domain wall, with the minimal stabilization time occurring in the vicinity of exceptional point. The parity-time phase transition can be observed by the oscillating-to-steady crossover of dynamics in the subspace orthogonal to the bound state. Furthermore, a concrete experimental proposal based on the trapped-ion setup is provided.

Controlling photon-mediated energy flow is central to the future of communications, thermal management, and energy harvesting technologies. Recent breakthroughs have revealed that many-body systems violating Lorentz reciprocity can sustain persistent photon heat current at thermal equilibrium, hinting at a paradigm of heat flow akin to superconductivity. Yet, the behavior of such systems far from equilibrium remains largely unexplored. In this work, we uncover the rich physics of radiative heat transfer in nonequilibrium, far-field many-body systems composed of thermal emitters that break Lorentz reciprocity. We show that the total heat flow naturally decomposes into two distinct components: an equilibrium term, which generates a persistent circulating heat current within the system, and a nonequilibrium term, which governs energy exchange with the environment. Remarkably, while the internal persistent heat current is ever-present, the nonequilibrium contribution can be precisely engineered to achieve perfect heat rectification and circulation. Our results open a route toward designing thermal systems with unprecedented control—unlocking the potential for lossless heat circulation and one-way thermal devices. This fundamentally shifts the landscape for next-generation thermal logic, energy conversion, and photonic heat engines.

We theoretically investigate the magnetic-multipole orders in two-dimensional (2D) altermagnets, focusing on two representative models: a generic minimal three-site model and a four-site model representative of monolayer FeSe. We construct low-energy effective Hamiltonians for both systems and calculate their respective multipole indicators to characterize the underlying magnetic order. Our analysis reveals an intriguing contrast between the two systems. We find that the generic minimal model exhibits the expected nonzero magnetic-octupole order. In the monolayer-FeSe model, however, the magnetic-octupole order vanishes globally, and a magnetic-hexadecapole order is present instead. The emergence of altermagnetic splitting in the band structure then arises via the interplay with a sublattice-isospin degree of freedom. Our work demonstrates how the classification and comprehensive understanding of 2D altermagnetic materials transcends bulk descriptions.

The capability of magnons to coherently couple with various quantum systems makes them an ideal candidate to build hybrid quantum systems. The optomagnonic coupling is essential for constructing a hybrid magnonic quantum network, as the transmission of quantum information among remote quantum nodes must be accomplished using light rather than microwave field. Here, we provide an optomagnonic continuous-variable quantum teleportation protocol, which enables the transfer of an input optical state to a remote magnon mode. To overcome the currently relatively weak coupling in the experiment, we introduce non-Gaussian distillation operations to enhance the optomagnonic entanglement and thus the fidelity of the teleportation. An auxiliary microwave cavity is adopted to realize the non-Gaussian and displacement operations on magnons. We show that a series of optical states, such as coherent, single-photon, squeezed, and cat states, can be teleported to the magnon mode. The work provides guidance for the experimental realization of magnonic quantum repeaters and quantum networks and a route to prepare diverse magnonic quantum states exploiting the photon-to-magnon quantum teleportation.

Feedback cooling plays a critical role in stabilizing quantum systems and achieving low temperatures, where a key question is to determine the fundamental thermodynamic limits on cooling performance. We establish a fundamental bound on quantum feedback cooling in Gaussian systems, by deriving a generalized second law of thermodynamics involving the kinetic temperatures of the system and a measure of quantum information flow obtained by continuous measurement. In contrast to previously known bounds, the obtained bound can be saturated by experimentally feasible situations using the quantum Kalman filter with a large feedback gain, where the cooling efficiency approaches its maximum. Our theoretical result is numerically demonstrated using parameters from an experiment of levitated nanoparticles. Our theory provides a general framework for understanding the thermodynamic constraints on quantum feedback cooling.

We introduce AppQSim, a benchmarking suite for quantum computers focused on applications of Hamiltonian simulation. We consider five different settings for which we define a precise task and score: condensed matter and material simulation (dynamic and static properties), nuclear magnetic resonance simulation, chemistry ground-state preparation, and classical optimization. These five different benchmark tasks display different resource requirements and scalability properties. We introduce a metric to evaluate the quality of the output of a tested quantum hardware, called distinguishability cost, defined as the minimal number of gates that a perfect quantum computer would have to run to certify that the output of the benchmarked hardware is incorrect.

Oblivious transfer is a fundamental cryptographic primitive that is useful for secure multiparty computation. There are several variants of oblivious transfer. We consider 1-out-of-2 oblivious transfer, where a sender sends two bits of information to a receiver. The receiver receives only one of the two bits, while the sender does not know which bit the receiver has received. Perfect quantum oblivious transfer with information-theoretic security is known to be impossible. We aim to find the lowest possible cheating probabilities. Bounds on cheating probabilities have been investigated for “complete” protocols, where if both parties follow the protocol, the bit value obtained by the receiver matches the sender's bit value. We instead investigate incomplete protocols, where the receiver obtains an incorrect bit value with probability $p_f$. We present optimal noninteractive protocols where Alice's bit values are encoded in four symmetric pure quantum states, and where she cannot cheat better than with a random guess. We find the protocols such that for a given $p_f$, Bob's cheating probability $p_r$ is as low as possible, and vice versa. Furthermore, we show that noninteractive quantum protocols can outperform noninteractive classical protocols and give a lower bound on Bob's cheating probability in interactive quantum protocols. Importantly for optical implementations, our protocols do not require entanglement nor quantum memory.

The large energy range and high intensity of current hadron accelerators, such as the Large Hadron Collider (LHC) and its planned high-luminosity upgrade, pose great challenges to beam measurements. The Beam Gas Curtain presents an accurate, minimally invasive profile monitor with a large energy range for high-intensity beams, by exploiting fluorescence from a supersonic gas jet interacting with the accelerator particle beam. In this paper, we report for the first time the proton and lead ion beam transverse profile and emittance continuously measured throughout the whole LHC energy range.

$\mathrm{La}{\mathrm{I}}_3$ has emerged as a promising scintillator due to its relatively small band gap. While some studies have explored various dopants to enhance its performance, there remains significant room for optimization, highlighting the importance of further understanding and tuning the intrinsic characteristics of $\mathrm{La}{\mathrm{I}}_3$. In this work, the crystal structure and properties of $\mathrm{La}{\mathrm{I}}_3$ are extensively investigated under high pressure up to 50 GPa. The ambient layered Cmcm-$\mathrm{La}{\mathrm{I}}_3$ is found to undergo an unexpected isostructural phase transition at ∼11 GPa, characterized by an anomalous change in the ratio of the $a$ to $b$ lattice parameters. This transition is further supported by Raman spectroscopy, electrical transport measurements, and first-principles calculations. Additionally, ultraviolet-visible absorption experiments indicate that the band gap of $\mathrm{La}{\mathrm{I}}_3$ gradually narrows and tends toward closure, eventually leading to a metallic state at 37 GPa. This work uncovers an interesting second-order phase transition among lanthanide halides, providing new insights into the fundamental behavior of $\mathrm{La}{\mathrm{I}}_3$ under high pressure.

Fast tuning of the transition frequency of superconducting qubits using magnetic flux is essential, for example, for realizing high-fidelity two-qubit gates with low leakage or for reducing errors in dispersive qubit readout. To apply accurately shaped flux pulses, signal distortions induced by the flux control lines need to be carefully compensated for. This requires their in situ characterization at the reference plane of the qubit. However, many existing approaches are limited in time resolution or in pulse duration. Here, we overcome these limitations and demonstrate accurate flux control with subpermille residual frequency errors on timescales ranging from nanoseconds to tens of microseconds. We achieve this by combining two complementary methods to characterize and compensate for pulse distortions. We have deployed this approach successfully in a quantum error correction experiment calibrating 24 flux-activated two-qubit gates. Reliable calibration methods, as the ones presented here, are essential in experiments scaling up superconducting quantum processors.

The topological characteristics of energy bands in crystalline systems are encapsulated in the Berry curvature of the bulk Bloch states. In photonic crystal slabs, far-field emission from guided resonances naturally provides a noninvasive way to probe the embedded wavefunctions, raising the question of how the information carried by escaping photons relates to the band topology. We develop a non-Hermitian model to describe the guided and leaky modes of photonic crystal slabs with long-range couplings and non-local responses. Within this framework, radiation Berry curvature is defined from the far-field polarization and compared to the conventional bulk Berry curvature of the crystal Bloch modes. We investigate this bulk-radiation correspondence in the vicinity of the $\mathrm{\Gamma }$ point of the square lattice and the $K$ point of the honeycomb lattice. The results show that the comparability between the bulk topology and the radiation topology is not universal; the validity is contingent upon the specific bulk Bloch states. Notably, the correspondence completely breaks down surrounding the far-field singularities, while it can hold in smooth regions under special symmetry conditions, e.g., inversion symmetry. Besides, net Berry curvature concentration is captured at the valleys of the nonlocal honeycomb lattice, facilitating further exploration on generalized topological phases in photonic lattices beyond the regimes with localized couplings and Hermiticity.

We propose a multisetting protocol for the detection of two-body Bell correlations and apply it to spin-nematic squeezed states realized in $f$ pairs of SU(2) subsystems within spin-$f$ atomic Bose-Einstein condensates. Experimental data for $f=1$, together with numerical simulations using the truncated Wigner method for $f=1,2,3$, demonstrate the protocol's effectiveness. We derive Bell inequalities tailored to collective observables of these subsystems and show how tuning interaction parameters controls the number of independent settings. Our findings extend multisetting Bell tests to high-spin ultracold ensembles, enabling scalable, flexible measurement configurations. This establishes a pathway to quantum metrology and information processing in tunable many-body platforms.

Chromium trihalides $\mathrm{Cr}{X}_3$ ($X=\text{Cl}$, Br, and I) have recently become a focal point of research due to their intriguing low-temperature, layer-dependent magnetic properties that can be manipulated by external stimuli. This makes them essential candidates for spintronic applications. Their magnetic orders are often related to the electronic structure parameters, such as spin-orbit coupling (SOC), Hund’s coupling ($J_H$), $p-d$ covalency, and interorbital Coulomb interactions. Accurately determining such parameters is paramount for understanding $\mathrm{Cr}{X}_3$ physics. We have used high-resolution resonant inelastic x-ray scattering spectroscopy to study $\mathrm{Cr}{X}_3$ across phase transition temperatures. Ligand field multiplet calculations were used to determine the electronic structure parameters by incorporating the crystal field interactions in a distorted octahedral orientation with $C_3$ symmetry. These methods provide the most detailed description of $\mathrm{Cr}{X}_3$ magneto-optical and electronic (energetic) terms to date. The crystal field distortion parameters $D\sigma$ and $D\tau$ were experimentally determined, and the energies of $d$ orbitals have been reported. The spectroscopic measurements reveal an energy separation between spin-allowed quartet states and spin-forbidden doublet states, which increases upon going from ${\mathrm{CrCl}}_3$ to ${\mathrm{CrI}}_3$. The role of SOC, for Cr $2p$ orbitals, in spin-flip excitations has been demonstrated. The determined $10Dq$ values are in good agreement with the spectrochemical series, and Racah $B$ follows the nephelauxetic effect. Such precise measurements offer insights into the energy design of spintronic devices that utilize quantum state tuning within two-dimensional magnetic materials.

The Mott insulator α$\text{−}\mathrm{RuC}{\mathrm{l}}_3$, featuring the intertwined interplay of spin-orbit coupling and Kitaev spin correlations, provides an unparalleled platform for probing quantum many-body physics. Using scanning tunneling microscopy/spectroscopy, we compare temperature-dependent $\mathit{dI}/\mathit{dV}$ spectra between in situ grown monolayers and exfoliated bulk samples. Both systems exhibit pronounced Mott gap softening near 110 K, manifested by spectral weight transfer from Hubbard bands toward the Fermi level, resulting in low-energy correlated charge delocalization. Although this gap softening coincides with Kitaev paramagnetic and structural phase transitions in bulk crystals, monolayer studies provide compelling insights. By eliminating structural phase transition in monolayer sample, we suggest that spin correlations, rather than Coulomb interactions alone, may govern charge dynamics within the Mott-Hubbard framework, challenging conventional Mott-Hubbard paradigms. These results resolve a long-standing controversy regarding the Mott gap magnitude in α$\text{−}\mathrm{RuC}{\mathrm{l}}_3$ and experimentally confirm the critical role of spin correlations in Mott physics.

Hamiltonian learning (HL), enabling precise estimation of system parameters and underlying dynamics, plays a critical role in characterizing quantum systems. However, conventional HL methods face challenges in noise robustness and resource efficiency, especially under limited measurements. In this work, we present Inverse Physics-Informed Neural Networks for Hamiltonian Learning (iPINN-HL), an approach that incorporates the Schrödinger equation as a soft constraint via a loss function penalty into the ML procedure. This formulation allows the model to integrate both observational data and known physical laws to infer Hamiltonian parameters with greater accuracy and resource efficiency. We benchmark iPINN-HL against a deep-neural-network-based quantum state tomography method [denoted as DNN-HL (Deep Neural Network for Hamiltonian Learning)] and demonstrate its effectiveness across several different scenarios, including one-dimensional spin chains, cross-resonance gate calibration, crosstalk identification, and real-time compensation to parameter drift. Our results show that iPINN-HL can approach the Heisenberg limit and exhibits robustness to noises, while outperforming DNN-HL in accuracy and resource efficiency. Therefore, iPINN-HL is a powerful and flexible framework for quantum system characterization for practical tasks.

In recent years, the investigation of synchronization in higher-order networks has emerged as a prominent area of research in nonlinear dynamics. In this work, we present a substantially generalized model of phase oscillators on globally coupled simplex structures that elucidate the formation mechanisms of strongly asymmetric synchronization clusters in complex systems characterized by many-body interactions. The strong asymmetric cluster synchrony involves three characteristics: (1) each cluster shows a different frequency band for the natural frequencies of the synchronized oscillators, (2) the phases of each cluster are locked to different interval sizes, and (3) the oscillators are nonuniformly distributed between the clusters. Focusing on a paradigmatic example of two coupled 2-simplex (three-body) interactions, we use the mean-field method to identify the existence of strongly asymmetric multicluster synchrony. Their solutions are analytically obtained through self-consistent equations. Our results also demonstrate, both theoretically and numerically, that the presence of asymmetric multicluster synchrony gives rise to multistability. When increasing the coupling strength, the system shows a transition to synchronization, which is then followed by synchronization fading, a complete loss of synchronization, and synchronization re-establishment. Our findings are not only limited to this case, but can also be extended to $n$-simplex interactions. Furthermore, we highlight that the inclusion of two-body interaction terms can disrupt the stability of the incoherent state, inducing spontaneous synchronization.

We propose a method to probe the thermal properties of quantum field theory (QFT) in an inflationary universe simulated by spin systems. Our previous work [Phys. Rev. Res. 7, 023197 (2025)] has demonstrated that QFT of Majorana fermions in an arbitrary two-dimensional spacetime can be mapped onto a spin system. In this study, we apply this mapping to investigate the thermal properties of an inflationary universe. An interaction between a quantum field and a detector allows one to extract information about the quantum field from the excitation probability of the detector, known as the Unruh-DeWitt detector. In an inflationary universe with Hubble constant $H$, the excitation probability of an Unruh-DeWitt detector follows a thermal distribution with temperature $H/\left(2\pi \right)$, indicating that a static observer in the inflationary universe perceives a thermal field. We consider a spin system corresponding to QFT in an inflationary universe and introduce a single spin interacting with this system as an Unruh-DeWitt detector. We demonstrate that the detector response asymptotically approaches the result of QFT with an appropriate power of the number of spin sites. Since the dynamics of spin systems can be implemented on programmable quantum simulation platforms, our study offers a concrete route toward experimentally probing the thermal properties of an inflationary universe in controlled quantum settings. This highlights the potential of quantum technologies to emulate and investigate aspects of quantum field theory in curved spacetimes.