Cation disorder is increasingly being studied as a means of tuning properties in electronic materials. Through Monte Carlo simulations and first-principles calculations, we determine the ranges of elastic moduli and polarization constants in $\mathrm{Zn}\mathrm{Ge}\mathrm{N}$${}_2$ as a function of ordering. We use heterostructure calculations to demonstrate a disorder-dependent type-I or type-II band offset between relaxed $\mathrm{Ga}\mathrm{N}$ and strained $\mathrm{Zn}\mathrm{Ge}\mathrm{N}$${}_2$ in the polar [001] direction. Modeling polarization and band offsets, we then use these calculations to comment on which values are desirable for device design, which parameters are obtainable through targeted growth techniques, and the challenges that remain in realizing a device and understanding cation disorder in heterostructures. Although the elastic and polarization properties change little with the order parameter, the band characteristics undergo dramatic shifts, creating a type-I band offset in partially disordered material.

Conventional acoustic metamaterial barriers are usually used to realize sound insulation for a continuous broad bandwidth. In some practical scenes, however, the noise signal from complex noise sources, such as gearboxes and motors, are usually complicated spectra with discrete peaks or valleys, instead of perfect continuous ones. In this case, the broadband design is unnecessary and may increase the thickness of metamaterials if too many frequency components are included. We need only a customized spectrum to achieve sound insulation at desired discrete frequencies, while, at other ones, insulation can be unwanted to preserve an effective signal other than noise. Here, we propose a customizable acoustic metamaterial barrier (CAMB) with intelligent and selective sound insulation. The CAMB is a composite structure consisting of a Helmholtz resonator (HR) and a microperforated panel (MPP) destined to control sound insulation at low frequencies, within 200–1000 Hz, and high-frequencies, within 1000–3000 Hz, respectively. An inverse process is proposed for customizable design. We use analytical and numerical methods to obtain the design libraries for the parameters of the HRs and MPPs. We numerically and experimentally demonstrate an example of a CAMB customized for a practical complex noise source. The sample has a thickness of 48 mm, approximately λ/11 for the lowest targeted frequency. The proposed customizable concept may pave the way for acoustic insulating metamaterials for complex sound sources with different frequency components.

Quantum systems must be prepared, controlled, and measured with high fidelity in order to perform complex quantum algorithms. Control fidelities have greatly improved in silicon spin qubits but state-preparation and readout fidelities have generally been poor. By operating with low electron temperatures and employing high-bandwidth cryogenic amplifiers, we demonstrate single-qubit readout visibilities $>99\mathrm{\%}$, exceeding the threshold for quantum error correction. In the same device, we achieve average single-qubit control fidelities $>99.95\mathrm{\%}$. Our results show that silicon spin qubits can be operated with high overall operation fidelity.

This work theoretically investigates the possibility of generating amplitude-squeezed light with high-quantum-efficiency interband cascade lasers. Based on a stochastic approach, we show that, by employing the suppressed-pump-noise configuration, this kind of midinfrared source enables operation with considerable amplitude squeezing over a large bandwidth of several GHz. Our results facilitate future midinfrared quantum photonic applications such as free-space secure communications.

Efficient manipulation of magnons for information processing is a central topic in spintronics and magnonics. An outstanding challenge for long-distance spin transport with minimal dissipation is to overcome the relaxation of magnons and to amplify the spin current they carry. Here, we propose to amplify magnon currents based on the realization of the bosonic Klein paradox in magnetic nanostructures. This paradox involves the antimagnon, carrying opposite spin and energy, the existence of which is usually precluded by ferromagnetic instabilities, as it is an excitation at negative energy. We show that by appropriately tuning the effective dissipation through spin-orbit torques, both magnons and antimagnons are dynamically stabilized. As a result, we find that the reflection coefficient of incident magnons at an interface between two coupled magnets can become larger than one, thereby amplifying the reflected magnon current. Our findings can lead to magnon amplifier devices for spintronic applications. Furthermore, our findings yield a solid-state platform to study the relativistic behavior of bosonic particles, which is an outstanding challenge with fundamental particles.

Topological systems are inherently robust to disorder and continuous perturbations, resulting in dissipation-free edge transport of electrons in quantum solids, or reflectionless guiding of photons and phonons in classical wave systems characterized by topological invariants. Realization of robust, lossless topological insulators in the technologically important terahertz (THz) frequency range has drawn immense attention. In this paper, we propose a Kagome lattice structure that supports topological edge states with valley-dependent transport. Optical topological insulators are subsequently fabricated, in which mirror symmetry is broken and degenerate states are lifted at $K(K^{\prime })$ valleys in the band structure. Theoretical and numerical analyses show that four types of edge states can be obtained. The performance of the fabricated topological waveguides is characterized with THz time-domain spectroscopy (TDS). Nearly identical THz wave transmission in the 0.437–0.453-THz range is verified with a straight-line topological waveguide and Z-shaped waveguides with multiple sharp turning corners, which quantitatively illustrate the strong backscattering suppression effects from the nontrivial topology edge states of the structures. Particularly, the THz TDS measurements provide important extra time-domain information about the topological waveguiding mode, which is generally unavailable from previous topological insulator investigations solely replying on power spectrum measurements.

The symmetrization postulate in quantum mechanics is formally reflected in the appearance of an exchange phase governing the symmetry of identical-particle global states under particle swapping. Many indirect measurements of this fundamental phase have been reported thus far, but a direct observation has been achieved only recently for photons. Here, we propose a general scheme capable of directly measuring the exchange phase of any type of particle (bosons, fermions, or anyons), exploiting the operational framework of spatially localized operations and classical communication. We experimentally implement it on an all-optical platform, providing a proof of principle for different simulated exchange phases. As a by-product, we supply a direct measurement of the real bosonic exchange phase of photons. Additionally, we analyze the performance of the proposed scheme when mixtures of particles of different nature are injected. Our results confirm the symmetrization tenet and provide a tool to explore it in various scenarios. Finally, we show that the proposed setup is suited to generating indistinguishability-driven $\mathrm{NOON}$ states useful for quantum-enhanced phase estimation.

The nitrogen-vacancy center (NVC) in a diamond is a promising platform for Floquet engineering. Using the synchronized readout, we investigate the NVC’s Floquet state driven by the Carr-Purcell sequence in a large-amplitude ac magnetic field. We observe the dynamics represented as Bessel functions up to 211th order in a systematic and quantitative agreement with the theoretical model. Furthermore, numerical calculations show that the effect of finite pulse duration and error limits the modulation amplitude available for Floquet engineering. This work provides an approach to precisely investigate Floquet engineering, showing the extendable range of modulation amplitude for two-level systems.

Networks of semiconducting single-walled carbon nanotubes (SWCNTs) are interesting thermoelectric materials due to the interplay between CNT and network properties. Here, we present a unified model to explain charge and energy transport in SWCNT networks. We use the steady-state master equation for the random resistor network containing both intra- and intertube resistances, as defined through their one-dimensional density of states that are modulated by static Gaussian disorder. The tube-resistance dependence on the carrier density and disorder is described through the Landauer formalism. Electrical and thermoelectric properties of the network are obtained by solving Kirchhoff’s laws through a modified nodal analysis, where we use the Boltzmann-transport formalism to obtain the conductivity, Seebeck coefficient, and electronic contribution to the thermal conductivity. The model provides a consistent description of a wide range of previously published experimental data for temperature and charge-carrier-density-dependent conductivities and Seebeck coefficients, with energetic disorder being the main factor to explain the experimentally observed mobility upswing with carrier concentration. Moreover, we show that, for lower disorder energies, the Lorentz factor obtained from the simulation is in accordance with the Wiedemann-Franz law for degenerate-band semiconductors. At higher disorder, deviations from simple band behavior are found. Suppressed disorder energy and lattice thermal conductivity can be the key to higher thermoelectric figures of merit, zT, in SWCNT networks, possibly approaching or even exceeding zT = 1. The general understanding of transport phenomena will help the selection of chirality, composition, and charge-carrier density of SWCNT networks to improve their efficiency of thermoelectric energy conversion.

High-performance interrogation of an inductor-capacitor microsensor has been a long-standing challenge due to the limited size of the sensor. Parity-time ($PT$) symmetry, an intriguing concept originated from quantum physics, has been utilized to improve the spectral resolution and sensitivity of the conventional readout circuit, while the $PT$-symmetry condition has to be satisfied. In this work, a sandwich-type wireless capacitance readout mechanism based on perturbed $PT$-symmetric electronic trimer without manual tuning of the reader circuit is proposed. Theoretical eigenvalue analysis by solving the system equations shows that the system exhibits single real mode in weak coupling regime whose eigenfrequency changes in response to the capacitance of the neutral resonator. Furthermore, the proposed readout system exhibits wider readout capacitance range compared to the standard $PT$-symmetry-based system while retaining higher $Q$ factor compared to the conventional readout method, which has been validated with the experimental prototype based on printed circuit board. Our work not only enriches the underlying theory of non-Hermitian physics, but also shows potential applications in scenarios where longer interrogation distance is required, such as implanted medical devices, parameter detection in harsh environment, etc.

The bowing of the energy of the three lowest band-to-band transitions in $\beta \text{−}({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3$ alloys is resolved using a combined density-functional theory (DFT) and generalized spectroscopic ellipsometry approach. The DFT calculations of the electronic band structure of both $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ and $\theta \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ allow the linear portion of the energy shift in the alloys to be extracted, and provide a method for quantifying the role of coherent strain present in the $\beta \text{−}({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3$ thin films on (010) $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ substrates. The energies of band-to-band transitions are obtained using the spectroscopic ellipsometry eigenpolarization model approach [A. Mock et al., Phys. Rev. B 95, 165202 (2017)]. After subtracting the effects of strain, which also induces additional bowing and after subtraction of the linear portion of the energy shift due to alloying, the bowing parameters associated with the three lowest band-to-band transitions in monoclinic $\beta \text{−}({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3$ are found.

Collective decision making is vital for recent information and communications technologies. In our previous research, we mathematically derived conflict-free joint decision making that optimally satisfies players’ probabilistic preference profiles. However, two problems exist regarding the optimal joint decision-making method. First, as the number of choices increases, the computational cost of calculating the optimal joint selection probability matrix explodes. Second, to derive the optimal joint selection probability matrix, all players must disclose their probabilistic preferences. Now, it is noteworthy that explicit calculation of the joint probability distribution is not necessarily needed; what is necessary for collective decisions is sampling. This study examines several sampling methods that converge to heuristic joint selection probability matrices that satisfy players’ preferences. We show that they can significantly reduce the above problems of computational cost and confidentiality. We analyze the probability distribution each of the sampling methods converges to, as well as the computational cost required and the confidentiality secured. In particular, we introduce two conflict-free joint sampling methods through the quantum interference of photons. The first system allows the players to hide their choices while satisfying the players’ preferences almost perfectly when they have the same preferences. The second system, where the physical nature of light replaces the expensive computational cost, also conceals their choices under the assumption that they have a trusted third party.

The grain-size effect of permittivity has been widely studied and its phenomenological theory is well established. In this work, we use such grain-size-effect theory to examine the grain-size effect of flexoelectricity, which has been overlooked so far. Two typical flexoelectric materials are employed, namely, ferroelectric ${\mathrm{Ba}\mathrm{Ti}\mathrm{O}}_3$ ceramics and paraelectric ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ ceramics. The results suggest that the variation of the intrinsic flexoelectric coefficient is completely synchronized with the variation of the grain-size-dependent permittivity for ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ ceramics. However, this synchronization is overturned in ${\mathrm{Ba}\mathrm{Ti}\mathrm{O}}_3$ ceramics, the flexoelectric coefficient of which increases with the grain size rather than dielectric permittivity. Under a flexoelectric field, it is proven that the polarization deflection of the 180° domains (more likely to exist for large grain sizes) dominates the flexoelectricity of ferroelectric ${\mathrm{Ba}\mathrm{Ti}\mathrm{O}}_3$ ceramics. The observed flexoelectric grain-size effect is beneficial for the design of bulk materials with a high flexoelectric coefficient and provides a simple and effective way to improve the performance of actuators and sensors based on bulk flexoelectricity.

Superconducting microwave circuits with Josephson junctions, the major platform for quantum computing, can only reach the full capability when connected. This requires an efficient protocol to distribute microwave entanglement. While quantum computers typically use discrete-variable (DV) methods for information encoding, the entire continuous-variable (CV) degree of freedom in electromagnetic fields must be utilized to achieve the highest entanglement distribution rate. Here, we propose a hybrid protocol to resolve the incompatibility between DV microwave quantum computers and CV quantum communications. CV microwave entanglement is distributed using optical swapping of optical-microwave entanglement pairs. To interface with DV microwave quantum computers, we further design a hybrid circuit to simultaneously convert and distill high-quality DV entanglement from noisy CV entanglement. The hybrid circuit is trained with machine-learning algorithms, ensuring high entanglement fidelity and generation rate. Our work not only provides a practical method to realize efficient quantum links for superconducting microwave quantum computers, but also opens avenues to bridge the gap between DV and CV quantum systems.

Strain and composition play a fundamental role in semiconductor physics, since they are means to tune the electronic and optical properties of a material and hence develop alternative devices. Today it is still a challenge to measure strain in epitaxial systems in a nondestructive manner, which becomes especially important in strain-engineered devices that often are subjected to intense stress. In this work, we demonstrate a microscopic mapping of the full tensors of strain and lattice orientation by means of scanning x-ray diffraction microscopy. We develop a formalism to extract all components of strain and orientation from a set of scanning diffraction measurements and apply the technique to a patterned ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ double layer to study strain relaxation and indium incorporation phenomena. The contributions due to varying indium content and threading dislocations are separated and analyzed.

The stochastic artificial neural network is widely studied nowadays, since it may address the critical issue of uncertainty quantification demanded in many application scenarios. At the hardware level, it calls for devices that can emulate stochastic weight-modification behaviors of synapses with high efficiency. In this work, we propose a stochastic spintronic synapse based on spin-torque-induced stochastic magnetic domain-wall (DW) dynamics, including stochastic DW generation by spin-transfer torque and deterministic DW motion induced by spin-orbit torque. The former plays the role of updating the synaptic weights stochastically, while the latter gives rise to multistates, namely, the analog property of the synapse. The proposed DW-based stochastic synapse requires few devices to implement sufficient resistance states. The neural-network-level simulation demonstrates that a spiking neural network based on these stochastic synapses is capable of classifying breast cancer data with a high accuracy of 95.7%.

Pulsating flows are common in many industrial, scientific, and natural fluidic systems. However, because the oscillatory flow component disturbs, e.g., optical measurements, deposition, or industrial processes, it is rarely desired. Moreover, in physiological conditions, pulsation control is desired. We explore the effect of using a plant-inspired nonlinear resistor to smooth the output of a peristaltic pump. Incorporating a 3D printed millifluidic biomimetic device reduces the oscillation amplitudes by 3 orders of magnitude, from $100\mathrm{\%}$ to $0.1\mathrm{\%}$ of the output flow rate. This represents a tenfold improvement relative to a purely linear resistive-capacitive approach. The observed flow kinetics compare well to a predictive model of peristaltic transport, allowing the further development of optimized fluid-handling systems driven by pulsatile flow. Applications to particle tracking and jetting are considered.

In conventional spintronic devices, ferromagnetic materials are used, which have a magnetization dynamics timescale of around nanoseconds, setting a limit for the switching speed. Increasing the magnetization switching speed has been one of the major challenges for spintronic research. In this work we take advantage of the ultrafast magnetic dynamics in ferrimagnetic materials instead of ferromagnets, and we use femtosecond laser pulses and a plasmonic photoconductive switch to create THz electrical pulses for ferrimagnetic switching by spin-orbit torque. By anomalous Hall and magneto-optic Kerr effect (MOKE) measurement, we demonstrate the robust THz-electrical-pulse-driven magnetization switching of ferrimagnetic $\mathrm{Gd}\text{−}\mathrm{Fe}\text{−}\mathrm{Co}$. The time-resolved MOKE shows more than 50-GHz magnetic resonance frequency of $\mathrm{Gd}\text{−}\mathrm{Fe}\text{−}\mathrm{Co}$, indicating faster than 20-ps magnetic dynamics. X-ray magnetic circular dichroism demonstrates the antiferromagnetically coupled $\mathrm{Fe}$ and $\mathrm{Gd}$ sublattices. Our work provides a promising route to realize ultrafast operation speed for nonvolatile magnetic memory and logic applications.