We propose an electrostatically coupled valley phononic metamaterial for three-axis inertial sensing (two accelerations, one rotation), which consists of unequal masses on the lattice sites to break the inversion symmetry. Different combination constructions of the metamaterials can form three types of interfaces hosting the valley edge states with distinct dispersion relations. A design strategy of assembling various interfaces is introduced to tailor the overall structure of a metamaterial for achieving three-axis inertial sensing. Critically, the acceleration induces the energy localization of the valley edge modes and the Coriolis force introduces additional phase differences into the vibration phase of masses. Hence, a three-axis inertial-sensing method based on the valley phononic metamaterial is proposed by tracking the mode shape shifts and the variation of phase difference between masses. The maximum cross-axis sensitivities of the sensing method are all below $0.4\mathrm{\%}$, underscoring the capability of three-axis independent sensing. The proposed valley phononic-metamaterial-based sensing method provides promising perspectives and avenues for the design of multiaxis inertial sensors.

With a variety of realizations, optomechanics utilizes its light-matter interaction to test fundamental physics. By coupling the phonons of a mechanical resonator to the photons in a high-quality cavity, control of increasingly macroscopic objects has become feasible. In such systems, state manipulation of the mechanical mode is achieved by driving the cavity. To be able to achieve high drive powers the system is typically designed such that it remains in a linear response regime when driven. A nonlinear response, and especially bistability, in a driven cavity is often considered detrimental to cooling and state preparation in optomechanical systems and is avoided in experiments. Here we show that with an intrinsic nonlinear cavity backaction cooling of a mechanical resonator is feasible operating deep within the nonlinear regime of the cavity. With our theory taking the nonlinearity into account, precise predictions on backaction cooling can be achieved even with a cavity beyond the bifurcation point, where the cavity photon number spectrum starts to deviate from a typical Lorentzian shape.

The fundamental aspect of the physics of ferroelectric materials is the screening of uncompensated bound charges by the dissociative adsorption of ionic charges from the environment. The adsorption of ions can be especially strong when the ferroelectric undergoes a temperature-induced transition from the paraelectric phase to the ferroelectric state. Here, we demonstrate that the adsorption of ions and free radicals by the polar surface of ferroelectric nanoparticles can be very efficient in aqueous solutions due to the strong ferro-ionic coupling in the nanoparticles. The obtained results can be useful for the development of alternative methods and tools for adsorption of the cations (${\mathrm{Li}}^{+},{\mathrm{K}}^{+},{\mathrm{Na}}^{+}$, etc.), anions (${\mathrm{Cl}}^{-},{\mathrm{Br}}^{-},{\mathrm{J}}^{-}$), and/or free radicals (${\mathrm{CO}}^{-}$, ${\mathrm{NH}}_4^{+}$, etc.) from aqueous solutions using lead-free uniaxial ferroelectric nanoparticles. The results may provide an alternative approach to the environment-friendly laboratory-scale purification of different aqueous solutions from ionic contamination using controllable cyclic temperature variations.

The linear relationship between the adsorption energies of different intermediates simplifies catalyst design; however, it simultaneously complicates the achievement of optimal performance in pure-phase materials. The perovskite oxide ${\mathrm{Sr}\mathrm{Mn}\mathrm{O}}_3$, characterized by its inherent dual $\mathrm{Mn}-\mathrm{O}$ coordination environment, is capable of overcoming the limitations through dual active-site cooperation effects. In this study, strain engineering was further applied to ${\mathrm{Sr}\mathrm{Mn}\mathrm{O}}_3$ to optimize the synergistic effect between the $\mathrm{Mn}-\mathrm{O}$ corner and $\mathrm{Mn}-\mathrm{O}$ face sites. Tensile strain enhances this synergy while reducing the adsorption strength of the intermediates, resulting in a decreased reaction energy barrier and improved oxygen-reduction reaction activity. Conversely, compressive strain has the opposite effect. The lowest overpotential of 0.23 V is achieved at a strain of 3%. Beyond this threshold, the synergy is disrupted due to significant lattice distortion. The design principles are conceptually validated by doping potassium atoms at the A site. The ΔG${}_{{}^{\ast }\mathrm{OH}}$ value has been identified as a key descriptor for the catalytic activity of ORR on ${\mathrm{Sr}\mathrm{Mn}\mathrm{O}}_3$. This study offers theoretical guidance for the design of high-activity, low-cost ORR catalysts.

Microwave frequency mixing is a fundamental functionality in microwave photonics, playing a crucial role in modern radar and wireless communication systems. Classical microwave photonic mixers require both the radio frequency (rf) signal and the local oscillator to be loaded onto the same optical light source, thereby impeding their capability in the context of distributed microwave systems. Using time-energy–entangled biphotons as the optical carrier, the quantum microwave photonic (QMWP) mixer offers a promising solution for attaining nonlocal mixing and surmounting such limitations. In this paper, we explore two types of QMWP mixer based on the configuration of the intensity modulators: cascade type and parallel type. Both QMWP mixers feature the properties of high linearity and dual outputs, with their spurious-free dynamic ranges being identical to that of the equivalent classical microwave photonic mixer. Specifically, the parallel-type QMWP mixer can nonlocally mix two physically separated rf signals, demonstrating its superiority in distributed microwave and millimeter-wave radar systems. Further, by application of multiphoton frequency-entangled sources as optical carriers, the nonlocal microwave frequency conversion capability endowed by the QMWP mixer can be extended to enhance the performance of multiple-path microwave mixing, which is essential for radar net systems.

Broadband correlated photon pairs (biphotons) are valuable in quantum metrology, but current generation methods either involve complex nonlinear structures or lack sufficient bandwidth and brightness. In this work, we theoretically describe and experimentally demonstrate an alternative technique for generation of a bright collinear biphoton field with a broad spectrum, achieved by using a tightly focused pump in a bulk nonlinear crystal. As the most straightforward application of the source, we employ Michelson interferometer-based quantum optical coherence tomography (QOCT). Utilizing the source enables the demonstration of record resolution and dispersion cancellation for this QOCT scheme.

Shadow tomography is a promising way for quantum system characterization, enabling the extraction of multiple properties of unknown quantum states using only single-copy randomized measurements. While single-copy measurements are experimentally friendly and efficient for estimating linear functions, they show limited efficiency for nonlinear ones. In contrast, multicopy measurements enabled by joint entangling operations can remarkably reduce the sample complexity for nonlinear functions. Here, we design and realize a deterministic optical three-qubit Fredkin gate by comprehensive control over multiple degrees of freedom of a single photon, achieving controlled-swap operation with high process fidelity of $0.935\pm 0.001$. Utilizing this Fredkin gate, we demonstrate hybrid shadow tomography, in which the higher-order functions like the moments can be efficiently estimated from the two-copy swap operation in conjunction with the single-copy randomized measurement. Our demonstration indicates a significant reduction in sample complexity compared with the single-copy setting. Furthermore, we show the potential advantage of our scheme in a proof-of-principle quantum metrology experiment, wherein the accuracy of parameter estimation is enhanced with the assistance of virtual distillation. Our results suggest that hybrid shadow tomography is an efficient and powerful tool for shadow-estimation-enabled quantum information processing.

We use first-principles electronic-structure theory to determine the intra- and intervalley electron-alloy scattering parameters in n-type $\mathrm{Ge}\text{−}\mathrm{Sn}$ alloys. These parameters are used to determine the alloy scattering contributions to the n-type electron mobility of $\mathrm{Ge}\text{−}\mathrm{Sn}$ at $300$ and $15\mathrm{K}$ using a first iteration of the Boltzmann transport equation in the relaxation-time approximation. For unstrained $\mathrm{Ge}\text{−}\mathrm{Sn}$, we find that an $\mathrm{Sn}$ concentration of at least $13.5\mathrm{\%}$ is needed to achieve an electron mobility greater than that of $\mathrm{Ge}$. Our results show that the mobility of $\mathrm{Ge}\text{−}\mathrm{Sn}$ can be over $25$ times that of $\mathrm{Ge}$, or ${10}^5{\mathrm{cm}}^2$/(Vs). At $15\mathrm{K}$, incorporation of less than $6\mathrm{\%}$ $\mathrm{Sn}$ into $\mathrm{Ge}$ quadruples its mobility, which suggests that $\mathrm{Ge}\text{−}\mathrm{Sn}$ has potential applications as a high-mobility 2D electron gas. Applying biaxial tensile strain to $\mathrm{Ge}\text{−}\mathrm{Sn}$ further increases the mobility and achieves this improvement at lower $\mathrm{Sn}$ content than in unstrained $\mathrm{Ge}\text{−}\mathrm{Sn}$.

The long-term evolution of an aqueous droplet containing pigments, viruses, ions, or polymers, and reaching the surface of a piece of wood, a piece of paper, a natural fabric, or a mask, governs the structure’s durability, the user’s comfort, the printing quality, or the development of bacteria or viruses. It is generally believed that this droplet spreads, penetrates the structure, stabilizes and eventually dries, following standard wetting and fluid mechanics. In this study, from nuclear magnetic resonance relaxometry and magnetic resonance imaging allowing water to be distinguished in its different states, it has been revealed that, instead of drying, the water is absorbed in nanoscale pores in the cellulose fibers and tends to diffuse throughout the entire structure in this particular state (bound water). Thus, the liquid water disappears from the pores before drying, while the nonabsorbed solute or particles remain stuck to the solid surfaces in the initial region of liquid penetration. A model was developed with the capability to predict the coupled transport of vapor and bound water through the structure, which quantitatively predicts the observations without any parameter fitting. This suggests changing the way we consider the fate of sweat, mist, ink, or rain on natural fabric clothing or biobased materials, and that we consider this diffusion as a potential major effect.

Semiconductor quantum dots (QDs) are a promising platform for multiple different qubit implementations, all of which are voltage controlled by programmable gate electrodes. However, as the QD arrays grow in size and complexity, tuning procedures that can fully autonomously handle the increasing number of control parameters are becoming essential for enabling scalability. We propose a bootstrapping algorithm for initializing a depletion-mode QD device in preparation for subsequent phases of tuning. During bootstrapping, the QD device functionality is validated, all gates are characterized, and the QD charge sensor is made operational. We demonstrate the bootstrapping protocol in conjunction with a coarse-tuning module, showing that the combined algorithm can efficiently and reliably take a cooled-down QD device to a desired global-state configuration in under $8$ min, with a success rate of $96\mathrm{\%}$. Finally, by following heuristic approaches to QD device initialization and combining the efficient ray-based measurement with the rapid radio-frequency reflectometry measurements, the proposed algorithm establishes a reference in terms of performance, reliability, and efficiency against which alternative algorithms can be benchmarked.

We present a design of a strained-topological-insulator spin-orbit-torque random-access-memory (STI SOTRAM) bit cell comprising a piezoelectric/magnet (gating)/topological insulator (TI)/magnet (storage) heterostructure that leverages the TI’s high charge-to-spin conversion efficiency coupled with the piezo-induced strain-based gating mechanism for low-power in-memory computing. The piezo-induced strain effectively modulates the conductivity of the topological surface state by altering the gating magnet’s magnetization from out of to in plane, facilitating the storage magnet’s spin-orbit-torque (SOT) switching. Through comprehensive coupled stochastic Landau-Lifshitz-Gilbert simulations, we explore the device dynamics, anisotropy-stress phase space for switching, and write conditions and demonstrate a significant reduction in energy dissipation compared to conventional heavy-metal-based SOT switching. Additionally, we project the energy consumption for in-memory Boolean operations (and and or). Our findings suggest the promise of the STI SOTRAM for low-power, high-performance edge computing.

We present thin-film niobium ($\mathrm{Nb}$) spiral resonators exhibiting large geometric inductance, high critical magnetic fields, and high single-photon quality factors. These low-loss geometric inductors can be a compelling alternative to kinetic inductors to create high-impedance superconducting devices for applications that require magnetic fields. By varying the spiral pitch, we realize resonators with characteristic impedances ranging from $3.25–7.09\mathrm{k}\mathrm{\Omega }$. We measure the temperature and magnetic-field-dependent losses and find that the high-impedance resonators maintain an intrinsic quality factor above approximately ${10}^5$ for parallel magnetic fields of up to 1 T. These properties make spiral $\mathrm{Nb}$ resonators a promising candidate for quantum devices that require circuit elements with high impedance and magnetic-field resilience.

The characterization of nonstabilizerness is fruitful due to its application in gate synthesis and classical simulation. In particular, the resource monotone called the stabilizer extent is a useful tool to estimate the simulation cost using rank-based simulators, one of the state-of-the-art simulators of Clifford+$T$ circuits. In this work, we propose faster numerical algorithms to compute the stabilizer extent. Our algorithm utilizes the column generation method, which iteratively updates the subset of pure stabilizer states used for calculation. This subset is selected based on the overlaps between all stabilizer states and a target state. In order to update the subset, we make use of a newly proposed subroutine for calculating the stabilizer fidelity that (i) achieves linear time complexity with respect to the number of stabilizer states, (ii) superexponentially reduces the space complexity by in-place calculation, and (iii) prunes unnecessary states for the computation. As a result, our algorithm can compute the stabilizer fidelity and the stabilizer extent for Haar random pure states up to $n=9$ qubits, which naively requires a memory of $305\mathrm{Ei}\mathrm{B}$. We further show that our algorithm runs faster when the target state vector is real. We prove that the problem size is reduced by $\mathcal{O}(2^n)$ compared to the general cases, which makes it computable for the case of $n=10$ qubits.

Anomalous Nernst (ANE) and spin Seebeck effects (SSE) are ubiquitous in conducting magnetic materials subject to temperature gradients. Their characterization in metallic systems is especially strenuous because of their indistinguishable symmetry. Here, we report on the accurate characterization of the ANE and SSE in $\mathrm{Fe}$-based multilayers at and above room temperature. We reveal that both effects consist of temperature-dependent and -independent components. At high temperatures, we provide evidence that the ANE decreases mainly due to reduced magnetization and spin polarization of free electrons, whereas the SSE increases owing to the enhanced thermal magnon density. We show that the relative strength of ANE and SSE can be tuned by thickness, stacking order, and doping concentration in various $\mathrm{Fe}$-based multilayers, opening the way for thermoelectric device engineering.

In spintronic terahertz (THz) emitters, THz radiation is generated by exciting an ultrafast spin current through femtosecond laser excitation of a ferromagnetic-nonmagnetic metallic heterostructure. Although an extensive phenomenological knowledge has been built up during the last decade, a solid theoretical modeling that connects the generated THz signal to the laser induced-spin current is still incomplete. Here, starting from general solutions to Maxwell’s equations, we model the electric field generated by a superdiffusive spin current in spintronic emitters, taking $\mathrm{Co}$/$\mathrm{Pt}$ as a typical example. We explicitly include the detector shape, which is shown to significantly influence the detected THz radiation. Additionally, the electron energy dependence of the spin Hall effect is taken into account, as well as the duration of the exciting laser pulse and the thickness of the detector crystal. Our modeling leads to realistic emission profiles and highlights the role of the detection method for distinguishing key features of the spintronic THz emission.

Magnon spintronics is an emerging field that explores the use of magnons, the quanta of spin waves in magnetic materials for information processing and communication. Achieving unidirectional information transport with fast switching capability is critical for the development of fast integrated magnonic circuits, which offer significant advantages in high-speed, low-power information processing. However, previous unidirectional information transport has primarily focused on Damon-Eshbach spin-wave modes, which are nonswitchable as their propagation direction is defined by the direction of the external field and cannot be changed in a short time. Here, we experimentally demonstrate a fast switchable unidirectional magnon emitter in the forward-volume spin-wave mode by a current-induced asymmetric Oersted field. Our findings reveal significant nonreciprocity and nanosecond switchability, underscoring the potential of the method to advance high-speed spin-wave processing networks.

Lead halide perovskite semiconductors have been revealed to exhibit high anharmonicity in their lattice dynamics, which has an important influence on associated carrier dynamic processes, including nonradiative carrier recombination. Anion vacancies in lead halide perovskites, which are one of the most common defects in halide perovskites, can create trap states and induce nonradiative recombination, impacting the photoelectric performance of perovskites. In this work, we demonstrate that the defect level of $V_X$ (X = $\mathrm{Cl}$, $\mathrm{Br}$, $\mathrm{I}$) in the mixed-anion perovskites $\mathrm{Cs}\mathrm{Pb}({\mathrm{Cl}}_x{\mathrm{Br}}_{1-x}{)}_3$ and $\mathrm{Cs}\mathrm{Pb}({\mathrm{Br}}_x{\mathrm{I}}_{1-x}{)}_3$ deepens with increasing composition x because of the elevated conduction band. Our results further show that $V_X$ in halide perovskites can easily capture electrons with a small energy barrier. In contrast, hole capture is much more difficult for $V_X$ due to pronounced lattice relaxations, which give rise to a high energy barrier. In the mixed-anion perovskites $\mathrm{Cs}\mathrm{Pb}({\mathrm{Cl}}_x{\mathrm{Br}}_{1-x}{)}_3$ and $\mathrm{Cs}\mathrm{Pb}({\mathrm{Br}}_x{\mathrm{I}}_{1-x}{)}_3$, the resulting lattice softening further increases the hole-capture barrier, thereby preventing $V_X$ defects from capturing holes. Therefore, through mixing anions in lead halide perovskites, nonradiative recombination caused by the halogen vacancy in perovskites can be significantly mitigated by enhanced anharmonic lattice relaxation and softening.

Quantum gate teleportation provides an approach to introduce nonlinear interactions between long-distance qubits, facilitating distributed quantum computation. We present two alternative protocols for deterministically teleporting controlled-not (cnot) and controlled-phase-flip (cpf) gates, using minimal resources—one entangled qubit (ebit) and two classical bits (cbits). Our protocols eliminate the need for local cnot gates at each party, which are typically required in the standard quantum circuit model [Eisert et al. Phys. Rev. A 62, 052317 (2000)]. Instead, by using a superposition of single-qubit gate orders, our approach makes quantum gate teleportation more experimentally feasible and flexible. Remarkably, the teleportation of the cpf gate and other two-qubit controlled unitary gates can be achieved by adjusting inherent single-qubit operations, reducing the need for single-qubit gates in cnot-based constructions. Additionally, we develop two optical architectures for the teleportation of these gates. The polarization-based and transverse spatial-based setups show that this approach is more feasible and practical, and pave a way for a distributed quantum computing network.