We demonstrate a method to generate photons by injecting hot electrons into a p-n junction within a $\mathrm{Ga}\mathrm{As}$/$\mathrm{Al}\mathrm{Ga}\mathrm{As}$ heterostructure. Hot electrons are generated by biasing across a mesoscopic potential in the n-type region and travel toward the p-type region through a quantum Hall edge channel in the presence of a magnetic field perpendicular to the substrate. The p-type region is created several microns away from the hot-electron emitter by inducing interfacial charges using a surface gate. The energy relaxation of the hot electrons is suppressed by separating the orbitals before and after longitudinal-optical phonon emission. This technique enables the hot electrons to reach the p-type region and to recombine with induced holes followed by photon emission. Hot-electron-induced hole recombination is confirmed by a peak around 810 nm in an optical spectrum that corresponds to excitonic recombination in a $\mathrm{Ga}\mathrm{As}$ quantum well. An asymmetric structure observed in the optical spectrum as a function of the magnetic field originates from the chiral transport of the hot electrons in the Hall edge channel. We propose that the combination of our technology and an on-demand single-electron source would enable the development of an on-demand single-photon source embedded in a semiconductor wafer, which could accelerate the integration of on-chip scalable quantum optical circuits.

Spaceborne telescopes are critical components of gravitational wave observatories. The interaction between wave front aberrations and spacecraft jitter produces significant tilt-to-length noise, which ultimately limits measurement sensitivity. Although the impact of wave front error has been extensively studied, the influence of aperture diffraction on tilt-to-length coupling remains insufficiently explored. In this paper, an efficient optical model based on Fresnel impulse response theory is developed to simulate diffraction effects in scientific interferometers. A systematic analysis is conducted on how the first 36 Zernike aberration modes and their cross-coupling affect optical path stability, leading to the derivation of a normalized sensitivity matrix that identifies critical aberration types. Through Monte Carlo simulations, the influence of wave front quality on tilt-to-length noise is further quantified under practical constraints. The results demonstrate that a targeted suppression of jitter-sensitive aberrations, particularly those with even radial orders, can substantially reduce coupling noise. These findings provide theoretical foundations and practical strategies for optimizing the wave front error budget in future space-based gravitational wave detection missions.

Spintronic devices, such as magnetic tunnel junctions (MTJs), offer nonvolatility and ultralow power operation, making them promising candidates for building physical reservoirs in neuromorphic computing. However, realizing low-power and hardware-integrable reservoir computing (RC) systems remains a major challenge. In this work, we construct an echo-state network based on voltage-controlled stochastic dynamics of ten distinct MTJs. These devices exhibit an S-shaped switching probability as a function of the driving-voltage pulse width, thereby offering the essential nonlinearity, stochasticity, and tunability required for RC. Moreover, by adopting a time-division-multiplexing strategy that integrates outputs from all ten distinct devices, we implement a reservoir with enhanced dynamical diversity. The resulting system achieves an accuracy of over 96% on the Modified National Institute of Standards and Technology (MNIST) task and reduces the normalized root-mean-square error (NRMSE) of the nonlinear autoregressive moving average (NARMA-10) task by about 35% compared with the single-device case. In addition, the MTJs exhibit a 50% switching time of about 660 ps and the energy consumption per switching event is estimated to be about 17.6 fJ at 2 V and 150 kΩ. This study demonstrates the feasibility of using voltage-pulse-controlled MTJs for RC and provides a practical pathway toward hardware-based neural network implementations.

Anisotropy, arising from reduced symmetry in material systems, has significant implications for both fundamental science and technological applications. Despite its importance, fully understanding and harnessing anisotropy for controlling spin current generation in practical scenarios has been challenging. In this study, we introduce an approach to generate anisotropic spin current, using facet-controlled anisotropic energy densities in yttrium iron garnet (${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$, YIG), through spin pumping and inverse spin Hall effect measurements. The cubic symmetry in YIG (001) generates a fourfold anisotropic spin current, which significantly influences spin pumping into the $\mathrm{Pt}$ layer. In contrast, the circular symmetry in YIG (111) results in an isotropic spin current. This leads to controlled anisotropic magnon transport, enabling the development of tunable magnonic devices and circuits.

Identification of neutron sources is central to nuclear physics and its applications, from planetary science to nuclear security, yet direct source discrimination from measured neutron spectra remains fundamentally elusive. Here, we introduce a Bayesian protocol that directly infers source ensembles from measured neutron spectra by combining full-spectrum template matching with probabilistic evidence evaluation. Applying this protocol to recoil and time-of-flight spectroscopy, we recover single- and two-source configurations with strong statistical significance (beyond $4\sigma$) at event counts as low as $\sim {10}^3$. These results demonstrate that neutron spectral signatures can be leveraged for robust source identification, opening a new observational window for both fundamental research and operationally driven applications.

Spectroscopic characterization is a key tool for determining carrier temperature in optoelectronic materials and devices. Assigning and extracting carrier temperature requires the assumption of quasiequilibrium, where carriers follow a Fermi-Dirac distribution. However, under low illumination intensities, carrier-carrier equilibration may be too slow for this assumption to hold. This is particularly relevant for hot carrier solar cells (HCSCs), which are required to operate under solar photon fluxes. Using a nonequilibrium model with a relaxation time approximation, we show that slow carrier-carrier scattering may distort temperature extraction from photoluminescence spectroscopy. Furthermore, our work shows that inefficient carrier-carrier equilibration in HCSCs leads to depletion of carriers at the extraction energies, resulting in a reduction in the extracted current and therefore the efficiency of the device. Our findings highlight the significance of considering carrier transport and scattering properties when evaluating and engineering candidate HCSC absorber materials.

The ingenious scheme we propose for achieving unidirectional reflection lasing (URL) onset involves integrating a one-dimensional defective atomic lattice with a coherent-gain atomic system. Its physical essence lies in the fact that the right-side reflectivity is drastically reduced due to the destructive interference between direct and secondary reflections, whereas on the left-side direct reflection is effectively suppressed and the secondary reflection is efficiently enhanced, ultimately reaching the lasing threshold. Through numerical results and further analyses, we have elucidated how to precisely tailor the lattice parameters and coupling fields to control the destructive-interference point, thereby enabling the onset and active modulation of URL. Our scheme not only effectively circumvents the stringent structural-parameter tuning process required to directly reach the URL onset, but also benefits the integration of active photonic devices into compact quantum networks and may improve the efficiency of optical information transmission.

A metamolecule comprising a metal double bar on a ferrite substrate exhibits nonreciprocal Fano resonance. A theoretical analysis demonstrates that the interaction between the two eigenmodes of the metamolecule depends linearly on the space- and time-inversion operations and the direction of the incident energy flow. Owing to these characteristics, the metamolecule exhibits nonreciprocal Fano resonance. Moreover, the difference in transmittance between forward and backward directions reaches the order of unity. Numerical and experimental studies confirm the theoretical findings. This study paves the way for realizing giant nonreciprocal Fano resonance with a single subwavelength structure.

Ultrathin oxide semiconductors with sub-1-nm thickness are promising building blocks for ultrascaled field-effect transistor (FET) applications due to their resilience against short-channel effects, high air stability, and potential for low-energy device operation. However, the n-type dominance of ultrathin oxide FET has hindered their integration into complementary metal-oxide-semiconductor (CMOS) technology, which requires both n- and p-type devices. Here, we develop an ab initio device-driven computational screening workflow to identify sub-1-nm-thickness oxide semiconductors for sub-5-nm FET applications. We demonstrate that ultrathin ${\mathrm{Ca}\mathrm{O}}_2$, $\mathrm{Ca}\mathrm{O}$, and $\mathrm{Sr}\mathrm{O}$ are compatible with p-type device operations under both high-performance (HP) and low-power (LP) requirements specified by the International Technology Roadmap of Semiconductors (ITRS), thereby expanding the limited family of p-type oxide semiconductors. Notably, $\mathrm{Ca}\mathrm{O}$ and $\mathrm{Sr}\mathrm{O}$ emerge as the first-of-the-kind sub-1-nm-thickness oxide semiconductors capable of simultaneously meeting the HP and LP criteria of the ITRS for both n- and p-type devices. $\mathrm{Ca}\mathrm{O}$ and $\mathrm{Sr}\mathrm{O}$ FETs outperform many existing low-dimensional semiconductors, exhibiting scalability below a 5-nm gate length. Our findings offer a pioneering effort in the ab initio, device-driven screening of sub-1-nm-thickness oxide semiconductors, significantly broadening the material candidate pool for future CMOS technology nodes.

In the noisy intermediate-scale quantum era, quantum devices can only execute shallow-depth circuits to maintain acceptable fidelity. This poses a significant challenge in implementing quantum algorithms that require interactions between nonadjacent qubits, especially on superconducting platforms with limited qubit connectivity. In conventional methods, swap gates are often employed to bridge distant qubits, at the cost of increased circuit depth and reduced overall fidelity. In this paper, we propose a scheme for implementing a controlled-$Z$ gate between next-nearest-neighbor qubits ($N^3\text{−}\mathrm{C}Z$), which enables direct high-fidelity entanglement between nonadjacent qubits without disturbing the intermediate qubit. Implemented on fixed-frequency and fixed-coupler superconducting qubits via simultaneous cross-resonance drives, the $N^3\text{−}\mathrm{C}Z$ gate achieves an average gate fidelity of 99.0% under realistic decoherence conditions, which is further confirmed by quantum process tomography with a fidelity of 98.9%. Moreover, we demonstrate that the $N^3\text{−}\mathrm{C}Z$ gate significantly reduces circuit depth and gate count in key quantum applications and circuit components, including quantum error correction, the quantum fan-out gate, the Toffoli gate, quantum ripple-carry adder, and graph state preparation. These results highlight the potential of the $N^3\text{−}\mathrm{C}Z$ gate as an efficient and hardware-friendly primitive for scalable quantum computation.

Rydberg atoms have emerged as a promising platform for physical implementation of quantum computation. Nonadiabatic holonomic quantum computation (NHQC) provides a powerful route toward high-fidelity and intrinsically robust quantum control. Here we propose a universal framework for robust quantum control based on geometric-optimized NHQC, enabling ultrafast and error-resilient quantum gates on Rydberg atoms. By optimizing geometric phases, we realize gate operations that effectively suppress Rabi-frequency errors while maximizing gate speed, thereby resolving the long-standing trade-off between robustness and evolution time encountered in previous optimized gate schemes. Numerical simulations on a Rydberg-atom platform show that our scheme achieves fidelities exceeding $99.999\mathrm{\%}$ for single-qubit gates and $99.94\mathrm{\%}$ for two-qubit entangling gates, even in the presence of decoherence and Rabi-frequency errors of up to $20\mathrm{\%}$. Therefore, our protocol offers a powerful path toward high-fidelity, error-resistant NHQC on the neutral-atom platform, with broad potential applications in scalable quantum information processing.

Imaging of spatial mode profiles is crucial for understanding the behavior of mechanical resonators. The recent development of phononic circuits has increased the demand for a fast imaging method based on principles of coherent detection. However, it becomes complicated to perform measurements on a large surface area. Here, we present a frequency-detuned collimated-beam interferometry measurement scheme with an in-plane spatial resolution of approximately $6\text{μ}\mathrm{m}$, which can provide information about the phase dynamics of the entire mechanical oscillation cycle on a timescale of a few seconds. We employ a stroboscopic pulse-probing method to resolve high-frequency vibrational motion with a standard CMOS camera. We use this setup to image megahertz frequency resonant mode profiles present in a valley-Hall topological triangular cavity, over an area of more than $20{\mathrm{mm}}^2$. We relate the obtained data to numerical simulations of the topological edge modes to reveal the relation between backscattering and the mode profile distribution. The presented protocol can become a staple for characterizing mesoscopic mechanical resonators.

The integration of photonic components into surface ion traps provides a scalable approach for trapped-ion quantum computing, sensing, and metrology, enabling compact systems with enhanced stability and precision. However, the introduction of optical apertures in the trap electrodes can distort the trapping electric field. This can lead to excess micromotion and ion displacement, which degrade the performance of quantum logic operations and optical clocks. In this work, we systematically investigate the electric field distortion in a surface ion trap with integrated waveguides and grating couplers that require apertures in the surface electrode using finite element method simulations. We analyze methods to reduce these distortions by exploiting symmetries and transparent conductive oxide materials.

A quantum network utilizes quantum entanglement and quantum error correction to effectively transmit quantum information. The development of such networks is a crucial step toward achieving secure and efficient quantum communication. This paper introduces a Bell inequality to verify nonlocality in continuous-variable (CV) multipartite chained entanglement-swapping networks, and proposes a CV-quantum key distribution (QKD) protocol for such networks with Bell-test gating, in which key generation proceeds only when the Bell test is passed. We analyze the achievable key rates under collective and coherent attacks. Numerical simulations show a clear scalability advantage, with the maximum secure distance increasing with the number of nodes. These results support the proposed CV-QKD protocol as a practical route to long-distance secure communication in CV quantum networks.

An emerging device architecture for infrared imaging is the curved focal-plane array, which benefits from several optical advantages over the traditional flat design. However, the curving process introduces additional strain in the active region, which must be taken into account. Type-II superlattices, a promising alternative to traditional bulk materials for use in infrared photodetectors, are candidate materials for use in these devices, but the transport properties of these highly heterogeneous materials are not straightforward and can be affected by different material conditions, such as superlattice (SL) disorder and external strain. We present a comprehensive study of the internal quantum efficiency (QE) calculated for a curved device that incorporates finite-element-analysis (FEA) modeling, nonequilibirium Green’s function (NEGF) calculations, and Gaussian process (GP) regression. FEA is used for predicting the strain configuration throughout the active region induced by the curving procedure of the device. NEGF is used to calculate the vertical hole mobility for a select set of strain configurations, from which the internal quantum efficiency of the device is approximated to predict performance under strained conditions. This data set is then used to train a GP model that maps the QE predictions onto the spatial coordinates of the curved device, based on the strain configuration predicted using FEA. This analysis is performed for ideal and disordered SLs to understand both the fundamental and practical limitations of the performance of these materials in curved devices.

We generalize the van der Pol oscillator model to account for a realistic nonlinearity of the resonant-tunneling-diode (RTD) $I$-$V$ curve. In the case of weak nonlinearity, perturbation theory is applied, and analytical expressions are derived for first-order corrections to the oscillation frequency, quadrature component (phase shift), and higher harmonics. Applicability requirements for perturbation theory are discussed. These requirements are always satisfied at sufficiently high frequencies, but they can fail already at frequencies as low as a few hundred GHz for RTDs with thicker barriers and at slightly above 500 GHz for thin-barrier RTDs, where oscillators transition to a strongly nonlinear regime. Calculation results for the above corrections for several RTD wafers, with typical parameters for sub-THz and THz oscillators, are presented. In particular, our calculations indicate that first-order correction terms play an essential role in the mechanism of variation of the RTD-oscillator frequency with bias. Taking into account the realistic nonlinearity of the RTD $I$-$V$ curve leads to significant quantitative and even qualitative differences in the behavior of RTD oscillators, compared to the conventional van der Pol oscillator model. The presented generalized model lays the groundwork for a more accurate analysis of nonlinear phenomena in RTD oscillators, it can serve as a reference for numerical simulations, it is also essential for qualitative and semiquantitative analysis of RTD oscillators.