Elastic metasurfaces are mostly conceived and designed based on gradient phase and thus suffering from parasitic scattering. Inspired by the advances of surface impedance model in acoustics, in this research, we establish an interface-impedance model to realize scattering-free modulation of elastic shear-horizontal (SH) waves. Anomalous refraction at large angle is successfully obtained through interface impedance. Meanwhile, focusing and Airy-beam generation are also investigated, which are mostly achieved by phase-based structures. We provide lossless or lossy forms of impedance to suppress parasitic waves. The establishment of boundaries with different shapes has been discussed. Finally, the simulated results of elastic metasurfaces composed of optimized units further validates the feasibility of impedance theory in achieving precise manipulation of SH waves.

Complementary magnon transistors (CMTs) are desired to effectively regulate the transport of coherent spin waves. Here, using comb-shaped gating electrodes with a variable duty ratio ($\delta$) and a gating current flowing through them, we were able to decrease or even increase the transmission of spin waves in a wide frequency range complimentarily. The reduction or amplification degree at opposite gating currents depends on $\delta$. We further found that interference between spin waves transmitted through the gated and ungated regions was responsible for the gate tunability at low $\delta$; at high $\delta$, the inhomogeneous temperature and magnetic fields introduced by the gating currents can nontrivially deflect spin waves and leads to an opposite gate tunability. Realization of the CMT based on a dc gating current may pave the way toward coherent magnon devices and circuits, spin-wave processing, or lensing applications.

A distributed quantum computing system requires a quantum communication channel between spatially separated processing units. In superconducting circuits, such a channel can be realized by using propagating microwave photons to encode and transfer quantum information between an emitter and a receiver node. Here we experimentally demonstrate a superconducting circuit that deterministically transfers the state of a data qubit into a propagating microwave mode, with a process fidelity of 94.5%. We use a time-varying parametric drive to shape the temporal profile of the propagating mode to be time symmetric and with constant phase, so that reabsorption by the receiving processor can be implemented as a time-reversed version of the emission. We demonstrate a self-calibrating routine to correct for time-dependent shifts of the emitted frequencies due to the modulation of the parametric drive. Our work provides a reliable method to implement high-fidelity quantum state transfer and remote entanglement operations in a distributed quantum computing network.

Efficient spintronic devices based on thin films need a full spin polarization at Fermi energy, ultralow magnetic damping, and magnetization perpendicular to the film plane. ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Si}$ and ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Ge}$ half-metal magnets Heusler compounds are good candidates due to their minority spin gap that leads to fully polarized current and ultralow magnetic damping. However, their low magnetocrystalline anisotropy leads to in-plane magnetization. One way to get perpendicular magnetic anisotropy in such Heusler compounds is to grow them on ${\mathrm{Mn}}_x\mathrm{Ga}$- or ${\mathrm{Mn}}_x\mathrm{Ge}$-buffer layers with the ${\mathrm{D}0}_{22}$ structure for which a strong magnetocrystalline anisotropy was reported. Here we first analyzed the impact of the stoichiometry of these binary alloys on their magnetic properties where the largest magnetocrystalline anisotropy was observed for the 3:1 stoichiometry. The replication of this perpendicular magnetic anisotropy in several half-metal magnet Heusler compounds epitaxially grown on top of them was thus analyzed by using standard magnetometry but also x-ray magnetic circular dichroism and in situ magneto-optic Kerr effect measurements. Squared hysteresis loops needed for applications were obtained using ${\mathrm{Mn}}_3\mathrm{Ge}$ with a coercive magnetic field that can be tailored by varying the different thicknesses in the stack. Our results also allowed us to explain some reported magneto-optic Kerr effect results not yet understood.

Many thermal measurements in high magnetic fields—including heat capacity, thermal conductivity, thermopower, magnetocaloric, and thermal-Hall-effect measurements—require thermometers that are sensitive over a wide temperature range, are low mass, have a rapid thermal response, and have a minimal easily correctable magnetoresistance. Here, we report the development of a granular-metal oxide ceramic composite (cermet) for this purpose formed by cosputtering of the metallic alloy nichrome ($\mathrm{Ni}$${}_{0.8}$$\mathrm{Cr}$${}_{0.2}$) and the insulator silicon dioxide ($\mathrm{Si}\mathrm{O}$${}_2$). We find that cosputtering of $\mathrm{Ni}$-$\mathrm{Cr}$ alloys with $\mathrm{Si}\mathrm{O}$${}_2$ in a reactive-oxygen plus inert-argon-gas mixture produces resistive thin-film thermometers sensitive enough to be used in calorimetry and related measurements from room temperature down to below 100 mK in magnetic fields up to at least 41 T.

Isolating noise in water relies on materials with low acoustic impedance. However, reducing the existing materials’ acoustic impedance severely compromises their stiffness and strength, resulting in a long-standing challenge of sound isolation in deep-sea environments with high ambient pressure. To overcome the mutual exclusion of low acoustic impedance and high mechanical properties, we propose a design principle including two steps that regulate the lattice orientation and incorporate a hierarchical morphology in an anisotropic metamaterial. Regulating the lattice orientation leads to low effective acoustic impedance while counterintuitively improving the initial stiffness. By learning from nature, incorporating a hierarchical morphology enables the metamaterial with an unprecedented decoupling characteristic that the mechanical strength can be enhanced independently from the acoustic impedance. A hierarchical metamaterial is constructed as a proof-of-concept demonstration and displays high sound transmission loss over 16 dB in a low and broad frequency range from 400 to 1200 Hz. Of note, the hierarchical metamaterial could maintain stable acoustic performance even under a high ambient pressure of 2 MPa. This work not only opens an alternative avenue for realizing sound isolation in deep-sea environments but also offers a design principle for metamaterials combining antagonistic functional properties.

Fano noise, readout noise, and the partial-charge-collection (PCC) effect collectively contribute to the degradation of energy spectra in charge-coupled device (CCD) measurements, especially at low energies. In this work, the x rays produced by the fluorescence of fluorine (677 eV) and aluminum (1486 eV) were recorded using a Skipper-CCD, which enabled the readout noise to be reduced to $0.2e^{-}$. Based on an analytical description of photopeak shapes resulting from the convolution of the PCC effect and Fano noise, we achieved a precise characterization of the energy spectra. This description enabled us to disentangle and quantify the contributions from both Fano noise and the PCC effect. As a result, we determined the Fano factor and the electron-hole pair creation energy. Additionally, we estimated the PCC region of the sensor and, for the first time, experimentally observed the expected skewness of photopeaks at low energies.

Time-dependent drives play a crucial role in quantum computing efforts with circuit quantum electrodynamics. They enable single-qubit control and entangling logical operations, as well as qubit readout. However, their presence can lead to deleterious effects such as large ac-Stark shifts and unwanted qubit transitions ultimately reflected into reduced control or readout fidelities. Qubit cloaking was introduced by Lledó et al. [C. Lledó, R. Dassonneville, A. Moulinas et al., Nat. Commun. 14, 6313 (2023)] to temporarily decouple the qubit from the coherent photon population of a driven cavity, allowing for the application of arbitrary displacements to the cavity field while avoiding the deleterious effects on the qubit. For qubit readout, cloaking permits us to prearm the cavity with an, in principle, arbitrarily large number of photons, in anticipation of the qubit-state-dependent evolution of the cavity field, allowing for improved readout strategies. Here, we take a closer look at two such strategies: first, arm-and-release readout, introduced together with qubit cloaking, where after arming the cavity, the cloaking mechanism is released and the cavity field evolves under the application of a constant drive amplitude; and, second, an arm-and-longitudinal readout scheme, where the cavity drive amplitude is slowly modulated after the release. We show that the two schemes complement each other, offering an improvement over standard dispersive readout for any values of the dispersive interaction and the cavity decay rate, as well as any target measurement integration time. Our results provide a recommendation for improving qubit readout without changes to the standard circuit-QED architecture.

Since Hanbury Brown and Twiss proposed intensity interferometry in 1956, light’s fluctuating nature, high-order coherence, and spatial correlations have become not only the cornerstones of quantum optics but also resources for many classical optical applications. Correlation-based optical metrologies, including ghost imaging and ghost diffraction, have distinct advantages ranging from local to nonlocal geometry, spatially coherent to incoherent light, and array to single-pixel sampling. In this paper we propose ghost diffractive deep neural networks (${\mathrm{GD}}^2\mathrm{NNs}$), a nonlocal optical information-processing system that combines traditional ghost diffraction with cascaded diffraction layers “learned” with use of diffractive deep neural networks. ${\mathrm{GD}}^2\mathrm{NNs}$ use light’s second-order coherence to enable image-free and interferometer-free coherent beam-demanded phase-object sorting with thermal light. Furthermore, ${\mathrm{GD}}^2\mathrm{NNs}$ convert the general encoder-decoder-detector cascaded framework into a parallel one, resulting in no optical interaction between the encoder and the decoder. As a proof-of-principle demonstration, we numerically and experimentally classify different phase objects using three-layer and two-layer ${\mathrm{GD}}^2\mathrm{NNs}$, respectively. This paper effectively provides a paradigm shift, particularly for diffraction-related coherent linear optical information processing systems, from spatially coherent to incoherent light and from cascaded to parallel processing.

The measurement of a wave function plays a pivotal role in quantum physics and presents a distinctive challenge in experiment. Recent works have shown that both the real and imaginary components of the wave function can be extracted by employing weak or strong measurements, thereby enabling the determination of its amplitude and phase. Here, we propose a simple approach for reconstructing the wave function utilizing the spin-orbit interaction of light at the air-glass interface. By directly measuring the amplitude and employing spatial differentiation to capture the phase gradient, it becomes possible to successfully reconstruct an unknown wave function. To demonstrate its feasibility, we experimentally measure the pure wave function of photons with a Gaussian state. Furthermore, we conduct measurements on a custom state featuring a targeted phase jump to examine the accuracy of our methodology. The measured results show a distribution with high contrast and considerable accuracy, with a fidelity that can exceed 85%. We believe that this work contributes valuable insights into the practical applications of spin-orbit interaction, including optical image processing, wave-front sensing, and quantitative phase imaging.

Interfacing the different building blocks of a future large-scale quantum network will require efficient and noiseless frequency conversion of quantum light. Nitrogen-vacancy centers in diamond are a leading candidate to form the nodes of such a network. However, the performance of a suitable converter remains a bottleneck, with existing demonstrations severely limited by parasitic noise arising at the target telecommunication wavelength. Here we demonstrate a platform for efficient low-noise quantum frequency conversion based on a monolithic bulk periodically poled potassium titanyl phosphate cavity and show its suitability for the conversion of 637-nm single photons from nitrogen-vacancy centers in diamond to telecommunication wavelengths. By resonantly enhancing the power of an off-the-shelf pump laser, we achieve an internal conversion efficiency of $(72.3\pm 0.4)\mathrm{\%}$ while generating noise of only $(110\pm 4)\mathrm{kHz}/\mathrm{nm}$ at the target wavelength without the need for any active stabilization. This constitutes a fivefold reduction in noise over existing state-of-the-art single-step converters at these wavelengths. We verify the almost-ideal preservation of nonclassical correlations by converting photons from a spontaneous-parametric-down-conversion source and moreover show the preservation of time-energy entanglement via Franson interferometry.

Although Rydberg-atom-based electric field sensing provides key advantages over traditional antenna-based detection, it remains limited by the need for a local oscillator (LO) for low-field and phase-resolved detection. In this work, we demonstrate that closed-loop quantum interferometric schemes can be used to generate a system-internal reference that can directly replace an external LO for Rydberg field sensing. We reveal that this quantum interferometrically defined internal reference phase and frequency can be used analogously to a traditional LO for atom-based down-mixing to an intermediate frequency for lock-in phase detection. We demonstrate that this LO-equivalent functionality provides analogous benefits to an LO, including full ${360}^{\circ }$ phase resolution as well as improved sensitivity. The general applicability of this approach is confirmed by demodulating a four-phase-state signal broadcast on the atoms. Our approach may open up new sensing schemes and although the present implementation still uses an auxiliary rf field, we provide a clear path toward all-optical Rydberg-atom sensing implementations by discussing several schemes that allow for all-optical rf phase detection without the need for an external rf LO field.

To describe charge-polarization coupling in the nanostructure formed by a thin ${\mathrm{Hf}}_x{\mathrm{Zr}}_{1-x}{\mathrm{O}}_2$ film with single-layer graphene as the top electrode, we develop the “effective” Landau-Ginzburg-Devonshire model. This approach is based on the parametrization of the Landau expansion coefficients for polar (ferroelectric) and antipolar (antiferroelectric) orderings in thin ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ films from a limited number of polarization-field curves and hysteresis loops. The Landau expansion coefficients are nonlinearly dependent on the film thickness, h, and $\mathrm{Zr}/[\mathrm{Hf}+\mathrm{Zr}]$ ratio, x, in contrast to h-independent and linearly-x-dependent expansion coefficients of classical Landau energy. We explain the dependence of the Landau expansion coefficients by the strong nonmonotonic dependence of the polar properties on the ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ film thickness, grain size, and surface energy. The proposed Landau free energy with five effective expansion coefficients, which are interpolation functions of x and h, describes the continuous transformation of polarization dependences on applied electric field and hysteresis loop shapes induced by changes to x and h in the range 0 < x < 1 and 5 nm < h < 35 nm. Using the effective free energy, we demonstrate that polarization of ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ films influences the graphene conductivity strongly, and the full correlation between the distribution of polarization and charge carriers in graphene is revealed. In accordance with our modeling, polarization of the 5–25-nm-thick ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ films, which are in ferroelectriclike or antiferroelectriclike states for chemical compositions of 0.35 ≤ x ≤ 0.95, determine the concentration of carriers in graphene and can control its field dependence. The result is promising for the creation of next-generation $\mathrm{Si}$-compatible nonvolatile memories and graphene-ferroelectric FETs, because the working voltages applied to the ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ film (which acts as a gate) can be relatively low (less than 2 V). These low voltages are sufficient to induce the pronounced hysteresis of ferroelectric polarization in the ${\mathrm{Hf}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_2$ gate, which, due to strong electric coupling, induces hysteresis of the graphene charge.

Integrated photonic chips have gradually become a significant option for information transmission and processing, in which the integration density will play an increasingly important role similar to that witnessed in integrated circuits. To date, great efforts have been made for silicon-on-insulator wafers to achieve dense integration with low crosstalk, although it remains quite challenging in the emerging lithium-niobate-on-insulator (LNOI) platform. Here, we report a strategy utilizing Floquet-mode-index modulation to realize broadband zero crosstalk with minimal impact on other performance metrics on the LNOI chips. The underlying physics of zero crosstalk is attributed to the collapse of the Floquet quasienergy, which is further experimentally verified by ultrabroadband low-crosstalk transmissions with low excess loss. Moreover, we demonstrate broadband eight-channel light transmissions in a compact LNOI waveguide array, showing an advantage over the conventional ones in comparison. Our work provides an alternative approach for improving the integration density of on-chip photonic circuits, opening up different possibilities for dense waveguide applications in the promising LNOI platform.

In this work we present a simulation of the semiconductor electrodes of photoelectrochemical (PEC) water-splitting cells based on the nonequilibrium Green’s function (NEGF) formalism. While the performance of simple PEC cells can be adequately explained with semiclassical drift-diffusion theory, the increasing interest towards thin-film cells and nanostructures, in general, requires theoretical treatment that can capture the quantum phenomena influencing the charge carrier dynamics in these devices. Specifically, we study a $p$-type ${\mathrm{Cu}}_2\mathrm{O}$ electrode and examine the influence of the bias voltage, reaction kinetics, and the thickness of the ${\mathrm{Cu}}_2\mathrm{O}$ layer on the generated photocurrent. The NEGF equations are solved in a self-consistent manner with the electrostatic potential from Poisson’s equation, sunlight-induced photon scattering and the chemical overpotential required to drive the water-splitting reaction. We show that the NEGF simulation accurately reproduces experimental results from both voltammetry and impedance spectroscopy measurements, while providing an energy-resolved solution of the charge carrier densities and corresponding currents inside the semiconductor electrode at nanoscale.

Twisted kagome lattices have unusual physical effects upon regulating the twist angle, an additional degree of freedom, which has drawn attention to these lattices. Here, we extend twisted kagome lattices to continuous elastomers and study the dynamics of flexural waves. We confirm that the twist angle can introduce boundary-obstructed topological insulators into topological trivial elastic kagome metamaterials by topological quantum chemistry theory. The kagome metamaterials have degenerate boundary states and twist-angle-dependent corner states. According to corner states corresponding to the inner angles of the modes, the corner states can be divided into two categories, obtuse-corner states and acute-corner states. The operating frequencies of the corner state corresponding to different inner angles are nondegenerate. The twist angle leads to rich and diverse regulations of the corner state. These results reveal hidden topological properties in trivial lattices and add an additional degree of freedom, the twisted angle, to tune higher-order topological insulators.

Frequency-mixing processes in spin systems have a variety of applications in meteorology and in quantum data processing. Spin spectroscopy based on frequency mixing offers some advantages, including the ability to eliminate crosstalk between driving and detection. We experimentally explore nonlinear frequency-mixing processes with negatively charged nitrogen-vacancy defects in diamond at low temperatures, and near level anticrossing. The experimental setup allows simultaneously applying magnetic driving in the longitudinal and transverse directions. Magnetic resonance detection is demonstrated using both Landau-Zener-Stückelberg interferometry and two-tone driving spectroscopy. The experimental results are compared with predictions of a theoretical analysis based on the rotating wave approximation.