Realizing large-scale quantum networks requires the generation of high-fidelity quantum entanglement states between remote quantum nodes, a key resource for quantum communication, distributed computation, and sensing applications. However, entanglement distribution between quantum network nodes is hindered by optical transmission loss and local operation errors. Here, we propose a quantum repeater architecture that synergistically integrates Rydberg-atom quantum processors with optical cavities to overcome these challenges. Our scheme leverages cavity-mediated interactions for efficient remote entanglement generation followed by Rydberg-interaction-based entanglement purification and swapping. Numerical simulations, incorporating realistic experimental parameters, demonstrate the generation of Bell states with 99% fidelity at rates of 1.1 kHz between two nodes in a local-area network (distance $0.1\mathrm{km}$), and can be extended to metropolitan-area ($25\mathrm{km}$) or intercity ($250\mathrm{km}$, with the assistance of frequency converters) networks with a rate of 0.1 kHz. This scalable approach opens up near-term opportunities for exploring quantum network applications and investigating the advantages of distributed quantum information processing.

Resonant-microstructure-based metastructures typically exhibit narrow effective bandwidths, and their operating frequencies are predominantly determined by the masses of the local resonators. This inherent limitation severely constrains the ability to manipulate low-frequency elastic waves. To overcome the limitations of mass dependence, an enhanced inertial amplification (IA) metastructure is proposed. The equivalent mass of the metastructure can be effectively increased without adding mass through the design of the linkages and hinges, thereby reducing the starting bandgap frequency and broadening the bandwidth. Eigenmode analysis further elucidates the physical mechanism underlying the formation of low-frequency bandgaps. Moreover, coupled bandgaps and strong wave-mitigation domains are obtained based on the spatial modulation of IA supercells. The proposed IA metastructure is employed to implement a one-dimensional topological insulator, thereby achieving low-frequency, robust, and wide-response-area topological interface states. This study is expected to promote the application of low-frequency, lightweight elastic-wave and acoustic devices in energy transport, energy harvesting, and vibration shielding.

Introducing flexible native entanglement gates can significantly reduce circuit complexity. We propose a gate integrating $i$swap and cphase operations within a single gate cycle. We theoretically show one possible realization of this gate for superconducting qubits using bichromatic parametric drives at distinct frequencies. We show how various parameters, such as drive amplitudes and frequencies, can control entanglement parameters. This approach enhances gate versatility, opening pathways for more efficient quantum computing.

Higher-order topological insulators, featured with multidimensional topologically protected boundary states, have attracted much research interest. However, in the existing higher-order topological insulators, topological corner states mostly emerge in a single band gap, which restricts their potential applications in photonics and acoustics. Here, a higher-order topological insulator hosting tri-band corner and edge states is proposed theoretically and realized experimentally based on a generalized honeycomb lattice where each sublattice site is generalized to a trimer. The triple topological band gaps are induced by the multiple degrees of freedom at each trimer, exhibiting enriched valley degrees of freedom and rich topological in-gap corner states when tuning the on-site energies. Both the numerical and experimental results demonstrate the existence of tri-band second-order corner states. The results may pave the way for multiband integrated acoustic devices.

Achieving fast and high-fidelity qubit operations is crucial for unlocking the potential of quantum computers. In particular, reaching low gate errors in two-qubit gates has been a long-standing challenge in the field of superconducting qubits due to their typically long duration relative to coherence times. To realize fast gates, we use the hybridization between fixed-frequency superconducting qubits with a strongly interacting coupler mode that is tunable in frequency. To reduce population leakage during required adiabatic passages through avoided level crossings, we employ a sensitivity-adaptive closed-loop optimization method to design complex pulse shapes. We compare the performance of Gaussian-square, Fourier-series, and piecewise-constant-slope pulse parametrizations and are able to reach 99.9% controlled-$Z$-gate fidelity using a 64-ns-long Fourier-series pulse defined by only seven parameters. These high-fidelity values are achieved by analyzing the optimized pulse shapes to identify and systematically mitigate signal-line distortions in the experiment. To improve the convergence speed of the optimization, we implement an adaptive cost function, which continuously maximizes the sensitivity. The demonstrated method can be used for tune-up and recalibration of superconducting quantum processors.

Self-assembled $\mathrm{In}\mathrm{Ga}\mathrm{As}$/$\mathrm{Ga}\mathrm{As}$ quantum dots (QDs) are of particular importance for the deterministic generation of spin-photon entanglement. One promising scheme relies on the Larmor precession of a spin in a transverse magnetic field, which is governed by the in-plane $g$ factors of the electron and the valence-band heavy hole. We probe the origin of heavy-hole $g$-factor anisotropy with respect to the in-plane magnetic field direction and uncover how it impacts the entanglement generated between the spin and the photon polarization. First, using polarization-resolved photoluminescence measurements on a single QD, we determine that the impact of valence-band mixing dominates over effects due to a confinement-renormalized cubic Luttinger $q$ parameter. From this, we construct a comprehensive hole $g$-tensor model. We then use this model to simulate the concurrence and fidelity of spin-photon entanglement generation with anisotropic hole $g$ factors, which can be leveraged by tuning the magnetic field angle and the excitation polarization. The results demonstrate that postgrowth control of the hole $g$ factor can be used to improve spin-photon cluster-state generation.

Andreev-spin qubits are a new qubit platform that merges superconductivity with semiconductor physics. The mechanisms dominating observed energy relaxation remain unidentified. We report here on three steps taken to address these questions in an $\mathrm{In}\mathrm{As}$ nanowire weak link. First, we designed a microwave readout circuit tuned to be directly sensitive to the spin-dependent inductance of the weak link so that higher orbital states are not necessary for readout—this resulted in larger windows in parameter space in which the spin-state properties can be probed. Second, we implemented a successful gap-engineering strategy to mitigate quasiparticle poisoning. Third, the weak link was fabricated by in situ shadow evaporation, which has been shown to improve atomic-scale disorder. We show how our design allows characterization of the spin stability and coherence over the full range of magnetic flux and gate voltage of an odd-parity bias point. The spin-relaxation and dephasing rates are comparable with those of the best devices previously reported, suggestive that surface atomic-scale disorder and quasiparticle poisoning are not linked to spin relaxation in $\mathrm{In}\mathrm{As}$ nanowires. Our design strategies are transferrable to novel materials platforms for Andreev qubits, such as germanium and carbon.

Analog Ising machines (IMs) occupy an increasingly prominent area of computer architecture research, offering high-quality, low-latency, and low-energy solutions to intractable computing tasks; however, IMs have a fixed capacity, with little to no utility in out-of-capacity problems. Previous works have proposed parallel, multi-IM architectures to circumvent this limitation [A. Sharma, et al., in Proceedings of the 49th Annual International Symposium on Computer Architecture, ISCA ’22 (Association for Computing Machinery, New York, NY, USA, 2022), p. 508; R. Santos, et al., Enhancing quantum annealing via entanglement distribution, ArXiv:2212.02465]. In this work, we theoretically and numerically investigate trade-offs in parallel IM networks to guide researchers in this burgeoning field. We propose formal models of parallel IM execution models, and we then provide theoretical guarantees for probabilistic convergence. Numerical experiments illustrate our findings and provide empirical insights into the high- and low-synchronization-frequency regimes. We also provide practical heuristics for parameter and model selection, informed by our theoretical and numerical findings.

We study the effect of magnetic domain wall curvature on its dynamics in the creep regime in systems displaying Dzyaloshinskii-Moriya interaction (DMI). We first derive an extended creep model that is able to account for the finite curvature effect in magnetic bubble domain expansion. We then discuss the relative importance of this effect and discuss its dependence on the main magnetic and disorder parameters. We show this effect can be easily measured in $\mathrm{Pt}$/$\mathrm{Co}$ multilayer samples, reporting a strong velocity reduction below a sample-dependent threshold value of the magnetic bubble radius. We finally show, both theoretically and experimentally, how the radius of magnetic bubbles can have a strong impact on the reproducibility of DMI measurements.

The torsion pendulum suspended by fused silica fiber has been widely utilized in gravitational experiments. For a practical torsion pendulum, which oscillates with a certain amplitude, the second-order, third-order, and higher-order terms of the angle should be considered, as a result, the quality factor ($Q$) is dependent on the amplitude. This work focuses on the nonlinearity of the fused silica fiber, whose $Q$ value reaches the order of magnitude of $1\times {10}^5$ or higher. The influence mechanism of amplitude on the $Q$ value of the torsion pendulum is analyzed using kinematics theory, and the amplitude modulation has been carried out to measure the coupling coefficient. Two fused silica fibers with diameters of 55 and 46 $\text{μ}\mathrm{m}$ are measured in turn, when the amplitude is reduced from tens of milliradians to several milliradians, the $Q$ value increases observably. The determined change coefficients ${\gamma }_0$ of two fused silica fibers are 0.031(3)/mrad and 0.030(2)/mrad, respectively, which agree well with each other. For the 55-$\text{μ}\mathrm{m}$-diameter fused silica fiber, the change rate of $Q$ value reaches $5.1(5)\times {10}^4/$mrad. This means that the $Q$ value is extremely dependent on the amplitude, thus this effect should be considered in gravitational experiments, especially in the evaluation of fiber anelasticity or to improve the measurement sensitivity of torque.

We propose an optimization scheme to maximize the secure key rate of a high-dimensional variant of BBM92. We use the position-momentum conjugate bases to encode the higher-dimensional qudits realized in a fully passive optical setup. The setup employs a single lens for the basis measurements and no lossy or slow elements. We optimize the qudit dimension for the protocol by maximizing the number of equiprobable sections (macropixels) of the detected beam while minimizing their overlap error. We show the enhanced key rate by discarding events from the ambiguous border pixels. Our strategy maximizes the overlap between the discarded regions from neighboring macropixels, thereby globally minimizing the overall loss and error. We calculate the optimal dimension and the secure key rate for certain beam parameters. We experimentally show the feasibility of our scheme. This work paves the way for realistic implementations of high-dimensional device-independent quantum key distribution with enhanced bit rates.

Material characterization, particularly three-dimensional (3D) surface-contour measurement, is essential for fully understanding and optimizing the performance of micro- and nano-structured devices. Point scanning confocal microscopy (PSCM) is a well-established 3D measurement technique, but it requires point-by-point scanning. Optical sectioning structured-illumination microscopy (OS-SIM), while faster and more cost-effective than PSCM, faces challenges when measuring samples with complex reflective properties, such as interreflection and subsurface scattering. This paper proposes confocal structured illumination microscopy (CSIM). CSIM uses the single-pixel imaging principle to separate indirect light signals caused by interreflection and subsurface scattering from the direct light signal of the conjugated object point. Subsequently, it applies the confocal imaging principle to extract direct light signals for confocal image reconstruction. Our experimental results demonstrate that, for samples with interreflection, CSIM effectively eliminates the artifacts caused by interreflection and accurately reconstructs the 3D contour of the measured sample, a task that OS-SIM struggles to accomplish. For samples with subsurface scattering, CSIM achieves a signal-to-background ratio (SBR) that is 3.5 times higher than that of OS-SIM. The proposed method enables precise 3D surface contouring of micro- and nano-structured samples with complex reflective properties. It has broad potential impacts in fields such as microelectronics, materials science, and mechanical engineering.

The selection of gate dielectric materials is critical in organic thin-film transistors (OTFTs), as carrier transport occurs at the semiconductor/gate dielectric interface, directly impacting device performance. In this study, we systematically investigate how gate dielectric surfaces affect both carrier transport and injection at the contacts in model inverted-coplanar or bottom-gate bottom-contact (BGBC), single-crystal OTFTs. We examine ten gate dielectric surfaces with relatively high hydrophobicity and classify their influence into three groups based on chemical structure and surface energy: (i) fluorinated polymers, (ii) silane coupling agents (SCAs) without phenyl rings, and (iii) hydrocarbons containing phenyl rings. Among these, OTFTs using fluorinated polymers (low surface energy) exhibited the highest mobility and the smallest subthreshold swing (SS), while devices with high surface energy dielectrics displayed reduced mobility or degraded subthreshold characteristics. The transfer-line method (TLM) and Kelvin probe force microscopy (KFM) revealed that contact resistance is highly sensitive to the gate dielectric, with the highest resistance observed in devices using phenyl-containing hydrocarbons with high surface energy. Importantly, when the effects of contact resistance are excluded, all the devices exhibited high intrinsic mobility. These findings highlight the pivotal role of gate dielectric surface properties in determining both carrier transport and injection, offering key insights for optimizing the performance of BGBC-type OTFTs.

We propose and demonstrate two cavity-assisted thermometry methods that exploit the sensitivity of cavity radiation to the position of the ion in the cavity mode to achieve highly sensitive temperature measurements. Our analysis allows us to determine the relative positions of the rf null and the cavity mode by the change of cavity emission at different positions of the ion in the cavity mode. By analyzing the second-order correlation function of the cavity emission, temperature measurements from near the motional ground state to over tens of millikelvin can be achieved and motion patterns of different frequencies can be characterized. We demonstrate our approach by measuring the temperature of a single ${}^{138}{\mathrm{Ba}}^{+}$ ion trapped in a fiber microcavity with a length of 230 $\text{μ}\mathrm{m}$ using both proposed methods, achieving comparable results.

We develop a method for entangling operations on nuclear spins surrounding a negatively charged boron-vacancy (V$\mathrm{B}$-center) point defect in hexagonal boron nitride (h$\mathrm{BN}$). To this end, we propose to employ the electron spin of a V$\mathrm{B}$ center as a control qubit. We show that, in the presence of a background magnetic field and by applying control pulses, one can collectively manipulate the state of the nuclei with ${\hat{U}}_z$ and ${\hat{U}}_x$ rotations. These rotations can serve for implementing the synchronous three-qubit $X$, $Z$, and Hadamard gates. Through our numerical analyses considering realistic system parameters and decoherence effects, we demonstrate that these gates can be executed with high fidelities. Furthermore, as an example for the application of our toolbox, we use these collective gates to prepare the highly entangled Greenberger-Horne-Zeilinger states among the three nuclear spins with a fidelity of 0.99. By including electron decoherence effects, we find that the relative deviations of the gate fidelities from the noisy terms are negligibly small, demonstrating the noise resilience of our protocols. Our work can serve as the foundation for exploiting the nuclear spins in h$\mathrm{BN}$ in future quantum technological applications.

Because of its exceptional optical and nonlinear properties, ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ has been widely adopted as a key semiconductor for optical communications, where effective thermal management is vital to ensure device performance and reliability. This study investigates the thermal conductivity of ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ based on ab initio calculations. By considering the contribution of wavelike phonons and the effect of four-phonon scattering, the calculated thermal conductivity of ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ at 300 K is $4.54\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$, which matches the experimental value of $4.63\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$. Wavelike mutually coherent phonons contribute significantly to thermal transport, with contributions as high as 25.6% to the total thermal conductivity at 900 K. Four-phonon scattering exhibits a limited but non-negligible impact on thermal conductivity, resulting in a reduction of 4.02%. Spectral analysis reveals that, for particlelike phonons, low-frequency modes from 0 to 6 THz contribute 81.5% to the thermal conductivity. This study clarifies phonon transport mechanisms in ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$, offering valuable guidance for device design.

Quantum crosstalk, which stems from unwanted interference of quantum operations with nearby qubits, is a major source of noise or errors in a quantum processor. In the context of shared quantum computing, it is challenging to mitigate the crosstalk effect between quantum computations being simultaneously run by multiple users since the exact spatiotemporal gate distributions are not apparent due to privacy concerns. It is therefore important to develop techniques for accurate detection and mitigation of crosstalk to enable high-fidelity quantum computing. Assuming prior knowledge of crosstalk parameters, we propose a time-adaptive detection method leveraging spectator qubits and multiple quantum coherence to amplify crosstalk-induced perturbations. We demonstrate its utility in detecting random sparsely distributed crosstalk within a time window. Our work evaluates its performance in two scenarios: simulation using an artificial noise model with gate-induced crosstalk and always-on idlings channels; and the simulation using noise sampled from an IBM quantum computer parameterized by the reduced Hamiltonian, stochastic, and affine (HSA) error model. The presented results show our method’s efficacy hinges on the dominance of single-qubit coherent noise across channels, and the effect of angle mismatching is suppressed as spectator qubits increase. From simulation using real-device noise parameters, our strategy outperforms the previous constant-frequency detection method of Harper et al. [arXiv:2402.02753] in the detection success rate, achieving an average detection success probability of $0.852\pm 0.022$ (equally scaled noise channels) and $0.933\pm 0.024$ (asymmetrically scaled noise channels) from one to seven crosstalk counts.