We present a method that integrates any quantum algorithm capable of finding solutions to integer linear programs into the branch-and-price algorithm, which is regularly used to solve large-scale integer linear programs with a specific structure. The role of the quantum algorithm is to find integer solutions to subproblems appearing in branch-and-price. Obtaining optimal or near-optimal integer solutions to these subproblems can increase the quality of solutions and reduce the depth and branching factor of the branch-and-price algorithm and hence reduce the overall running time. We investigate the viability of the approach by considering the tail assignment problem and the quantum approximate optimization algorithm (QAOA). Here, the master problem is the optimization problem set partitioning or its decision version exact cover and can be expressed as finding the ground state of an Ising spin glass Hamiltonian. For exact cover, our numerical results indicate that the required algorithm depth decreases with the number of feasible solutions for a given success probability of finding a feasible solution. For set partitioning, on the other hand, we find that for a given success probability of finding the optimal solution, the required algorithm depth can increase with the number of feasible solutions if the Hamiltonian is balanced poorly, which in the worst case is exponential in the problem size. We therefore address the significance of properly balancing the objective and constraint parts of the Hamiltonian. We empirically find that the approach is viable with QAOA if polynomial algorithm depth can be realized on quantum devices.

Although the drift-diffusion model (DDM) is fundamental in semiconductor physics and related fields, the accurate solution of the DDM is unavailable over a long period of time. The DDM is accurately and analytically solved based on the Fermi-Dirac statistics and general mobility model. The differences in current values, carrier density, and electric field functions between the accurate solution, other solutions, and the standard Scharfetter-Gummel (SG) scheme are evident. The results for mobility extracted from the accurate solution are larger and evidently different from those of the SG scheme, Mott-Gurney equation, and the analytic solution under the uniform-electric-field approximation.

Antiferromagnets (AFMs) are promising materials for future high-frequency field-free spintronic applications. Self-localized spin structures can enhance their capabilities and introduce alternative functionalities to AFM-based devices. Here we consider a domain wall (DW), a topological soliton that bridges a connection between two ground states, similar to a Josephson junction link between two superconductors. We demonstrate the similarities between DWs in biaxial AFM with easy-axis primary anisotropy, driven by a spin current, and long Josephson junctions (LJJs). We found that the Bloch line (BL) in DWs resembles the fluxon state of Josephson junctions, creating a close analogy between the two systems. We propose a scheme that allows us to create, move, read, and delete such BLs. This transmission line operates at room temperature and can be dynamically reconfigured in contrast to superconductors. Results of a developed model were confirmed by micromagnetic simulations for ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{Dy}\mathrm{Fe}\mathrm{O}}_3$, i.e., correspondingly with weak and strong in-plane anisotropy. Overall, the proposed scheme has significant potential for use in magnetic memory and logic devices.

In this study, we present the fabrication and characterization of $\mathrm{Ni}$/${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$/$\mathrm{Ni}$ trilayers using rf sputtering. These trilayers exhibit thick $\mathrm{Ni}$ layers (10 $\text{μ}\mathrm{m}$) and excellent adherence to the substrate, enabling high magnetoelectric coefficients. By engineering the magnetic anisotropy of nickel through anisotropic thermal residual stress induced during fabrication, and by selecting a carefully chosen cut angle for the ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ substrate, we achieved self-biased behavior. We demonstrate that these trilayers can power medical implant devices remotely using excitation by a small ac magnetic field, thereby eliminating the need for a dc magnetic field and bulky magnetic field sources. The results highlight the potential of these trilayers for the wireless and noninvasive powering of medical implants. This work contributes to the advancement of magnetoelectric materials and their applications in healthcare technology.

Ultrafast light-matter interaction has emerged as a powerful tool to control and probe the macroscopic properties of functional materials, especially two-dimensional transition metal dichalcogenides that can form different structural phases with distinct physical properties. However, it is often difficult to accurately determine the transient optical constants. In this work, we developed a near-infrared pump—a terahertz to midinfrared (12–22 THz) probe system in transmission geometry to measure the transient optical conductivity in $2H{\text{−}\mathrm{Mo}\mathrm{Te}}_2$ layered material. By performing separate measurements on bulk and thin-film samples, we are able to overcome issues related to nonuniform substrate thickness and penetration depth mismatch and to extract the transient optical constants reliably. Our results show that photoexcitation at 690 nm induces a transient insulator-metal transition, while photoexcitation at $2\text{μ}\mathrm{m}$ has a much smaller effect due to the photon energy being smaller than the band gap of the material. Combining this with a single-color pump-probe measurement, we show that the transient response evolves towards the $1T^{{}^{\prime }}$ phase at higher fluence. Our work provides a comprehensive understanding of the photoinduced phase transition in the $2H{\text{−}\mathrm{Mo}\mathrm{Te}}_2$ system.

Using analytical and numerical means, we document a geometry-enabled phenomenon, termed herein dispersion morphing, in which lattice stretching in rotator structures modifies the real and imaginary dispersion characteristics of the system. We then demonstrate diverse functionality derived from dispersion morphing under adiabatic (static) and nonadiabatic (dynamic) lattice deformation, to include dramatic changes in group velocity, refractive index, directivity, and amplification. The proposed rotator lattices consist of in-plane rotators coupled by angled elastic linkages the location and spacing of which can be easily reconfigured, allowing significant changes in the dispersion characteristics of the lattices. Under adiabatic lattice deformation, we reconfigure the directivity and refractive index of the periodic structure and present a closed-form solution to achieve flat bands across the entire wave-number domain. We also incorporate chirality in the unit-cell design to counteract pass-band shifting in the process of dispersion morphing, such that a real-time wave manipulation becomes possible. For dynamic lattice deformation, we model the lattice constant as (i) a step function of time and (ii) a harmonic function of time. In the former scenario, we employ the concept of temporal interfaces and achieve on-demand time delay of the propagation. In the latter scenario, we demonstrate a parametric amplification effect with stretching-informed amplification parameters. We report strong agreement between our theoretical analysis and numerical simulations, verifying the aforementioned findings. We believe that the versatile adaptations of such rotator lattices and their rich dynamics may inspire next-generation reconfigurable and multifunctional metamaterial devices.

We propose superconducting-semiconducting (super-semi) qubit and coupler designs based on high-quality compact through-silicon vias (TSVs) to overcome challenges introduced by materials and processing required to fabricate high-quality super-semi Josephson junctions. In our designs, an interposer “probe” wafer containing TSVs is used to contact a sample wafer with, e.g., a superconductor-proximitized epitaxially grown germanium quantum well. By utilizing the capacitance of the probe-wafer TSVs, the majority of the electric field in the qubits is pulled away from lossy regions in the semiconducting wafer, such as the graded buffer layers sometimes required for epitaxial growth. Through simulations, we find that the probe wafer can reduce the electric field participation of the qubit in the sample wafer by an order of magnitude for thin substrates and remains small even when the epitaxial-layer thickness approaches $100\mu \mathrm{m}$. We also show how the qubit-coherence improvements achieved via this scheme are extensible to multiqubit systems that have tunable qubit-qubit couplings without magnetic fields. This approach additionally shrinks the on-chip footprint of voltage-tunable superconducting qubits while homogenizing critical wiring structures independent of semiconducting materials, which could aid in accelerating the understanding of super-semi heterostructures in a variety of systems.

We perform a study of the transport properties of cubic boron nitride at low to high electric fields based on calculations performed by density-functional theory and full-band ensemble Monte Carlo. The full band structure and the carrier-phonon scattering rates are computed from first principles using density-functional theory with a hybrid functional and density-functional perturbation theory, respectively. The results of these calculations are used in an ensemble Monte Carlo simulator to calculate the velocities, energies, and impact ionization coefficients in different crystallographic directions. In conjunction, we have also developed the form-factor parameters to recreate the full band structure based on the empirical pseudopotential method, which is less computationally expensive and more accessible. The results of the transport calculations performed using the two differently computed band structures are compared.

The cryogenic hardware required to build a superconducting-qubit-based quantum computer demands a variety of microwave components. These elements include microwave couplers, filters, amplifiers, and circulators and/or isolators. Traditionally implemented as discrete components, integration of this peripheral hardware, in an effort to reduce overall footprint, thermal load, and added noise, is a key challenge to scaling modern quantum processors with qubit counts climbing over the one hundred plus mark. Ferrite-based microwave isolators, generally employed in the readout chain to decouple qubits and resonators from readout electronics, persist as one of the volumetrically largest devices still utilized as discrete components. Here, we present an alternative two-port isolating integrated circuit derived from the dc superconducting quantum interference device (dc SQUID). Nonreciprocal transmission is achieved using the three-wave microwave-mixing properties of a flux-modulated dc SQUID. We show that when multiple dc SQUIDs are embedded in a multipole admittance-inverting filter structure, the three-wave mixing derived from the flux pumping of the dc SQUIDs can provide directional microwave power flow. For a three-pole filter device, we experimentally demonstrate a directionality greater than 15 dB over a 600-MHz bandwidth.

The proton-boron (pB) reaction has attracted extensive interest for confinement fusion since it produces energetic $\alpha$ particles without neutrons. Based on the pitcher-catcher geometry, a scheme to achieve a high-yielding pB nuclear reaction is proposed, where a meshed catcher target is used. The hot electrons generated by the interaction between laser and pitcher target induce a sheath field in the meshes that accelerates protons in the catcher target to drive a nuclear reaction. Not only is the number of protons increased because the action area of the sheath field becomes larger, but also the energy of protons is well controlled to meet the optimal value by adjusting the size of the mesh based on laser intensity. Two-dimensional particle-in-cell simulations show that our scheme has a 6-times improvement in the yield of nuclear reaction compared with the traditional solid catcher target. With a further increase of laser intensity, the gain of nuclear reaction yield also increases. Our approach provides an idea for the research of laser-driven pB nuclear reaction studies and compact $\alpha$ sources.

Surface acoustic waves (SAWs) provide an efficient dynamical coupling between strain and magnetization in micro- and nanometric systems. Using a hybrid device composed of a piezoelectric, GaAs, and a ferromagnetic Heusler alloy thin film, ${\mathrm{Fe}}_3\mathrm{Si}$, we are able to quantify the amplitude of magnetoacoustic waves generated with SAWs via magnetic imaging in an x-ray photoelectron microscope. The cubic anisotropy of the sample, together with a low damping coefficient, allows for the observation of resonant and nonresonant magnetoelastic coupling. Additionally, via micromagnetic simulation, we verify the experimental behavior and quantify the magnetoelastic shear strain component in ${\mathrm{Fe}}_3\mathrm{Si}$, which appears to be large ($b_2=10\pm 4{\mathrm{MJm}}^{-3}$).

Understanding the nature of active sites and the catalytic properties of oxide-supported bimetallic clusters under reaction conditions remains challenging. In this study, we combine first-principles calculations with genetic algorithm and grand canonical Monte Carlo methods to reveal the structures and compositions of ${\mathrm{Ce}\mathrm{O}}_2$-supported $\mathrm{Cu}$-based bimetallic clusters in an oxygen-rich environment. Oxidized ${\mathrm{Cu}}_4{X}_4$ (X = $\mathrm{Pd}$, $\mathrm{Pt}$, and $\mathrm{Rh}$) bimetallic clusters on ${\mathrm{Ce}\mathrm{O}}_2(111$) are stable and exhibit different catalytic properties during $\mathrm{CO}$ oxidation compared with the pristine bimetallic clusters. Microkinetic simulations predict that ${\mathrm{Ce}\mathrm{O}}_2(111)$-supported ${\mathrm{Cu}}_4{\mathrm{Pd}}_4{\mathrm{O}}_{10}$, ${\mathrm{Cu}}_4{\mathrm{Pt}}_4{\mathrm{O}}_{11}$, and ${\mathrm{Cu}}_4{\mathrm{Rh}}_4{\mathrm{O}}_{14}$ clusters have much higher $\mathrm{CO}$ oxidation activity than the supported ${\mathrm{Cu}}_4{\mathrm{Pd}}_4$, ${\mathrm{Cu}}_4{\mathrm{Pt}}_4$, and ${\mathrm{Cu}}_4{\mathrm{Rh}}_4$ clusters; this is ascribed to the moderate $\mathrm{CO}$ adsorption strength and active oxygen on oxidized alloy clusters. A mechanistic study suggests that $\mathrm{CO}$ oxidation occurs via the ${\mathrm{O}}_2$ associative reaction mechanism on the ${\mathrm{Cu}}_4{\mathrm{Pd}}_4{\mathrm{O}}_{10}$ and ${\mathrm{Cu}}_4{\mathrm{Pt}}_4{\mathrm{O}}_{11}$ clusters, while it proceeds through the ${\mathrm{O}}_2$ dissociative reaction mechanism on the ${\mathrm{Cu}}_4{\mathrm{Rh}}_4{\mathrm{O}}_{14}$ cluster. Our calculations further predict that $\mathrm{CO}$ oxidation on the ${\mathrm{Cu}}_4{\mathrm{Rh}}_4{\mathrm{O}}_{14}$ cluster exhibits a low apparent activation energy, indicating that the oxidized cluster possesses excellent $\mathrm{CO}$ oxidation activity. This work demonstrates that the catalytic activity and reaction mechanism vary with the composition and oxidation state of the alloy nanocluster under the reaction conditions and emphasizes the influence of the reaction atmosphere on the reaction mechanisms and catalytic activity of oxide-supported alloy catalysts.

We study relaxation processes in dipolar-coupled negatively charged nitrogen-vacancy ($\mathrm{N}$-$V^{-}$) centers close to zero field. Specifically, we uncover regimes where flip-flop and double-flip processes, as well as mixing induced by local electric fields, play a significant role in $\mathrm{N}$-$V$–$\mathrm{N}$-$V$ cross relaxation. Our results are relevant for understanding decoherence in many-body spin systems, as well as for high-sensitivity magneto- and electrometry with long-lived interacting solid-state spins. As a proof of principle, we present an orientation and microwave-free magnetometer based on cross relaxation.

Accurate characterization of the single-photon detection efficiency (SPDE) of single-photon detectors (SPDs) is an essential but nontrivial task for various applications. Conventional methods require detailed detector models to calculate the estimated SPDE, which are not always available. To overcome this limitation, we propose a generalized method based on decoy state for accurate characterization of SPDE with experimental demonstration and verification in this work. The decoy-state scheme uses only three weak laser intensities to probe the response of an SPD and calculate rigorous bounds on the background noise and SPDE without prior knowledge of the detector model. To show the versatility, the decoy-state scheme is applied to the single-photon avalanche diode and the homodyne detector. The effects of time-dependent noise and multiphoton response to our scheme are analyzed. The experimental results show that the effects of time-dependent noise can be eliminated, and an accuracy bound of efficiency can be achieved with a bound range of 2.6%. The relaxed assumptions on the detector model, straightforward measurement process, rigorous calculation, and high accuracy, could open possibilities for our generalized toolbox as a device calibration standard, fundamental physics research, quantum information, lidar, and biomedical applications.

This paper solves a long-standing problem in resonant ultrasound spectroscopy (RUS) for cubic solids through the use of two-dimensional deep learning (DL). By means of inverse methods, conventional RUS can determine all independent elastic constants of a crystalline solid specimen by comparing measured and calculated free-vibration resonance frequencies. However, to avoid invalid local minima in the inverse process, good initial guesses of the elastic constants must be available. Here, we propose a DL scheme to remedy this problem, which utilizes an input elasticity image composed of three layers obtained from resonance frequency data. After network training, this scheme is executed in two steps: DL processing by a neural network to output elastic constants in a Blackman diagram classification, followed by the use of a regression network around the classified point in this diagram for more accurate determination. By means of simulations, we demonstrate that this DL scheme yields the principal elastic constants within an error of approximately $5\mathrm{\%}$ without any inverse processing even in the unfavorable case of five missing modes for 111 existing cubic crystals.

In recent years, optical control of mechanical oscillators has emerged as a critical tool for everything from information processing to laser cooling. While traditional forms of optomechanical cooling utilize systems comprising discrete optical and mechanical modes, it has recently been shown that cooling can be achieved in a chip-based system that possesses a continuum of modes. Through Brillouin-mediated phonon-photon interactions, cooling of a band of traveling acoustic waves can occur when anti-Stokes scattered photons exit the system more rapidly than the relaxation rate of the mechanical waves, to a degree determined by the acousto-optic coupling. Here, we demonstrate that a continuum of traveling-wave phonons can be cooled within an optical fiber, extending this physics to macroscopic length scales. Leveraging the large acousto-optic coupling permitted within a liquid-core optical fiber, heterodyne spectroscopy reveals power-dependent changes in spontaneous-Brillouin-scattering spectra that indicate a reduction of the thermal phonon population by 21 K using 120 mW of injected laser power. These results provide alternative ways to manipulate phonon populations that could enable acousto-optic applications with reduced noise or provide ways to control traveling-wave phonons at the quantum level.

Understanding the mechanical behavior of rocks is crucial in subsurface activities, including storage of carbon dioxide and hydrogen gases, which both rely on shale caprocks as potential sealing barriers. Several current large-scale initiatives focus on potential carbon storage in North Sea aquifers. The Draupne Formation contains a series of shale layers interbedded with sandstone layers, the overall thickness of which varies in the range from tens to hundreds of meters. Injection of carbon dioxide into the underlying sandstone reservoirs leads to changes in the surrounding stress field, which can result in fault reactivation or the creation of microfractures, and thus, alter the performance of the shale caprock. Time-resolved microcomputed tomography (4D $\text{μ}$CT) has, in recent years, become a powerful technique for studying the mechanical properties of rocks under stress conditions similar to those prevailing in geological reservoirs. Here, we present results from experiments performed on Draupne shale using a triaxial rig combined with 4D $\text{μ}$CT based on synchrotron radiation. Detailed mechanical analysis of the tomography datasets by digital volume correlation reveals the three-dimensional pattern of the temporally evolving deformation field. Intermittent bursts of deformation at different locations within the specimen are observed, which eventually evolve into a major fracture plane extending laterally across the whole sample. This study suggests that the pseudolinear-elastic-appearing behavior in the macroscopic stress-strain relationship previously reported for Draupne shale samples could consist of a series of irreversible processes occurring at various weak points within the sample. The combination of 4D $\text{μ}$CT imaging with strain analysis enables in situ investigations of deformation processes via quantification of shear and volumetric strains within the sample, thus providing an improved understanding of the fracture dynamics of shales.

Nanowire lasers can be monolithically and site-selectively integrated onto silicon photonic circuits. To assess their full potential for ultrafast optoelectronic devices, a detailed understanding of their lasing dynamics is crucial. However, the roles played by their resonator geometry and the microscopic processes that mediate energy exchange between the photonic, electronic, and phononic subsystems are largely unexplored. Here, we study the dynamics of $\mathrm{Ga}\mathrm{As}$-$\mathrm{Al}\mathrm{Ga}\mathrm{As}$ core-shell nanowire lasers at cryogenic temperatures using a combined experimental and theoretical approach. Our results indicate that these NW lasers exhibit sustained intensity oscillations with frequencies ranging from $160\text{GHz}$ to $260\text{GHz}$. As the underlying physical mechanism, we have identified self-induced electron-hole plasma temperature oscillations resulting from a dynamic competition between photoinduced carrier heating and cooling via phonon scattering. These dynamics are intimately linked to the strong interaction between the lasing mode and the gain material, which arises from the wavelength-scale dimensions of these lasers. We anticipate that our results could lead to optimised approaches for ultrafast intensity and phase modulation of chip-integrated semiconductor lasers at the nanoscale.

Variational algorithms have received significant attention in recent years due to their potential to solve practical problems using noisy intermediate-scale quantum (NISQ) devices. A fundamental step of these algorithms is the evaluation of the expected value of Hamiltonians, and hence efficient schemes to perform this task are required. The standard approach employs local measurements of Pauli operators and requires a large number of circuits. An alternative is to use entangled measurements, which might introduce additional gates between physically disconnected qubits that harm the performance. To solve this problem, we propose hardware-efficient entangled measurements (HEEMs), that is, measurements that permit only entanglement between physically connected qubits. We show that this strategy enhances the evaluation of molecular Hamiltonians in NISQ devices by reducing the required circuits without increasing their depth. We provide quantitative metrics of how this approach offers better results than local measurements and arbitrarily entangled measurements. We estimate the ground-state energy of the ${\mathrm{H}}_2\mathrm{O}$ molecule with classical simulators and quantum hardware using the variational quantum eigensolver with HEEM.