Quantum state transmission and quantum information transmission (QIT) through fiber channels hold immense promise for advancing the scope of quantum information applications. However, besides unavoidable transmission loss, channel noise accelerates the decoherence of quantum states and severely limits the transmission distance in practical continuous-variable quantum state transmission. To address the issue of channel noise in metropolitan quantum fiber-optic links, we propose a scheme called dual-channel transferring after interference. This scheme exhibits immunity to additional channel noise while maintaining sufficient communication capacity. Based on this scheme, we experimentally achieve the transmission of a $-5.9$-dB squeezed state at 1.3 $\text{μ}\mathrm{m}$ through 3 km of optical fiber. We obtain a $-3.2$-dB output squeezed state and demonstrate that this decrease is solely attributable to channel loss, independent of channel noise. Incidentally, we achieve an improved measurement sensitivity of guided acoustic-wave Brillouin scattering noise in a fiber channel exploiting squeezed light. In addition, beyond its simplicity of installation and ease of operation, this approach also offers the highest transmission capacity compared with the existing QIT technologies. Our scheme is suitable for almost all modulation-free continuous-variable quantum information protocols, such as quantum secret sharing, quantum entanglement swapping, and some quantum key distribution schemes with entangled states, as well as participating in the construction of future quantum networks.

Optical logic operations are pivotal for optical signal processing and digital computing, enabling rapid parallel computation. However, traditional optical logic operations often adhere to the electronic logic paradigm, representing logic variables based on intensity distribution. These methods contain limitations regarding the range of logic functions and energy consumption. Herein, we introduce linear polarization (LP) modes as optical logic variables, offering a departure from these constraints by harnessing the weakly coupled processing of the two-dimensional asymmetric spatial distribution of LP modes. The weak coupling mechanism within LP modes empowers the diffractive deep neural network (D${}^2$NN) to accomplish coupling conversion between lateral and longitudinal components. This not only surmounts the limitations in conventional LP mode processing but also significantly enhances the degree of modulation freedom with minimal energy loss. Through establishing linear mapping relationships for input and output LP mode vectors, our study demonstrates that a three-layered D${}^2$NN successfully executes fundamental logical operations (AND, OR, and NOT) alongside combined logic operations (NAND and NOR). Numerical results showcase a diffraction efficiency exceeding 92%, with mode purity surpassing 97%. In addition, by integrating AND and OR logic operations within a single D${}^2$NN, we achieve modal purity exceeding 97%. These findings confirm the potential of employing the D${}^2$NN for logical operations on weakly coupled LP modes, offering promising avenues for precise manipulation of other intricate modal fields.

Superconducting logic is fast and energy efficient relative to CMOS but also fundamental studies are needed to scale up circuits for greater utility. Recently, ballistic shift registers for single-flux quanta (SFQ) bits have been shown in simulations to allow high-efficiency superconducting gates. However, these gates are unpowered, such that the bits slow after each gate operation and thus only a short sequence of gates is possible without added power. Here, we theoretically show that a circuit based on an Aharonov-Casher ring can power these shift registers by boosting the bit velocity to a constant value, despite their unusual bit states constituted by two polarities of SFQ. Each bit state is forced into a different ring arm and then accelerated as part of the operation. The circuit dynamics depend on various circuit parameters and choices of how to merge the bit-state paths. One design from each merge design choice is proposed to possibly enable scaling up to an array of gates by adding serial biasing in a relatively simple way. We find adequate performance for ballistic logic in terms of boosted velocity, energy efficiency, and parameter margins. We also discuss the classical barriers of the circuit, which relate to the Aharonov-Casher effect in a different parameter regime.

The perpendicular magnetic anisotropy (PMA) of metal/ferromagnet (FM)/oxide trilayers is known to depend on the degree of oxidation of the FM/oxide interface. Among the different methods to tune the PMA, magnetoionics is emerging as a promising technique with potential applications in low-power spintronic devices. In this work, the PMA of $\mathrm{Pt}$/$\mathrm{Co}$/${\mathrm{Al}\mathrm{O}}_x$/${\mathrm{Hf}\mathrm{O}}_2$ capacitorlike devices was gradually tuned by electric field gating. Hard-x-ray photoelectron spectroscopy (HAXPES) measurements at a synchrotron radiation source, guaranteeing tunable photon energies, a collimated beam, and a large photon flux, have allowed us to probe the composition of the cobalt ultrathin film buried below the dielectric layer of the capacitors, and its evolution upon the application of the gate voltage. The $\mathrm{Co}$ $2p$ HAXPES spectra of the gated devices were compared to those obtained for $\mathrm{Pt}/\mathrm{Co}/{\mathrm{Al}\mathrm{O}}_x$ reference samples, for which the PMA was controlled by tuning the $\mathrm{Co}$ oxidation with oxygen plasma. For similar magnetic anisotropy states, the two types of samples exhibit equivalent $\mathrm{Co}$ $2p$ HAXPES spectra, with the same weight of metallic Co and $\mathrm{Co}\mathrm{O}$ signatures. These results constitute direct experimental proof that, in our integrated devices, the gate voltage modifies the PMA through the modification of the oxidation state of the buried cobalt layer driven by oxygen-ion migration.

Controlling near-field heat transport is crucial for the development of alternative energy applications. In recent years, the application of an external magnetic field to actively control noncontact heat transport has emerged as a highly appealing technique, and some exotic subwavelength-scale thermomagnetic phenomena have been predicted, especially in magneto-optical (MO) dipole systems. Here, we report two additional near-field thermomagnetic effects that can occur in macroscopic planar MO many-body systems. First, we predict an extremely large thermal magnetoresistance for nanoscale heat transport in a simple MO configuration comprising several interacting $\mathrm{In}\mathrm{Sb}$ planar slabs. It is found that the thermal resistance at room temperature can be substantially increased up to the order of 10 000% with a relatively strong magnetic field. We elucidate that this striking variation benefits from the multibody planar architecture, which allows us to transform an effective energy tunneling arising from zero-field cavity surface modes into a feeble tunneling mediated by field-induced hyperbolic modes. We also show the possibility of reducing the required field through structural optimization. Subsequently, we predict a magnetic-field-driven transition between superdiffusive and ballistic transport by further examining the radiative transport regime in a periodic $\mathrm{In}\mathrm{Sb}$ many-slab configuration under the action of external fields. This peculiar transition is associated with a field-induced alteration in the polarization of the dominant modes of transport. Our predicted thermomagnetic effects not only enrich the community of many-body energy transport but also provide guidelines for the development of advanced thermal management of elegant MO multibody architectures.

We propose a terahertz quantum illumination (QI) scheme utilizing emissions from free-electron lasers (FELs) based on joint photon number measurement and quantum state discrimination using maximum a posteriori estimation. We analyze the performance of our QI scheme and quantify it with error probabilities. We numerically demonstrate the quantum advantage of our QI scheme over classical illumination. Our work paves the way to using FELs as entangled photon sources for quantum illumination in the terahertz regime.

Particle-induced x-ray emission (PIXE) is a well-established ion-beam analysis technique, enabling quantitative measurement of the elemental composition of a sample surface under an ambient atmosphere with an external beam, which significantly simplifies the measurements, and is strictly necessary for those samples that cannot sustain a vacuum environment. Few-MeV electrostatic proton accelerators are used today in PIXE systems. We present here an external beam PIXE methodology based on a compact laser-driven proton accelerator. A 10-TW class ultrashort laser is used to generate a few-MeV proton beam, and a compact transport magnetic beamline is used to collect and transport the proton beam and to prevent unwanted fast electrons from reaching the sample. An x-ray CCD camera in single-photon detection mode is used to retrieve the spectrum of radiation emitted by the samples upon proton irradiation in air. Elemental composition analysis is performed and validated against standard energy-dispersive x-ray spectroscopy, demonstrating quantitative and accurate external beam PIXE analysis with compact laser-driven accelerators.

The accurate computation of properties of large molecular systems is classically infeasible and is one of the applications in which it is hoped that quantum computers will demonstrate an advantage over classical devices. However, due to the limitations of present-day quantum hardware, variational-hybrid algorithms introduced to tackle these problems struggle to meet the accuracy and precision requirements of chemical applications. Here, we apply the quantum computed moments (QCM) approach combined with a variety of noise-mitigation techniques to an eight qubit and spin-orbital representation of the water molecule (${\text{H}}_2\text{O}$). A noise-stable improvement on the variational result for a four-excitation trial state (circuit depth 25, 22 cz gates) was obtained, with the ground-state energy computed to be within $1.0\pm 0.8$ mHa of exact diagonalization in the 14 spin-orbital basis. Thus, the QCM approach, despite an increased number of measurements and noisy quantum hardware (cz error rates c.0.3% corresponding to expected error rates on the trial-state circuit of order 7%), is able to determine the ground-state energy of a nontrivial molecular system at the required accuracy (c.0.05%). To the best of our knowledge, these results are the largest calculations performed on a physical quantum computer to date to achieve millihartree agreement with exact diagonalization, and a promising indicator of how such hybrid approaches might scale to problems of interest in the low-error and fault-tolerant regimes as quantum computers develop.

The feasibility of zirconium doping of $\alpha$-${\mathrm{Ga}}_2{\mathrm{O}}_3$ grown by pulsed laser deposition is demonstrated. Targets with different zirconium contents are used to adjust the zirconium content in the thin films. Therefore, a two-step growth process is utilized, where first an undoped $\alpha$-${\mathrm{Ga}}_2{\mathrm{O}}_3$ thin film is grown as a high-temperature buffer layer and the zirconium-doped $\alpha$-${\mathrm{Ga}}_2{\mathrm{O}}_3$ layer is subsequently deposited at a lower growth temperature. Highly conductive thin films are obtained with resistivities as low as $3.3\times {10}^{-3}\mathrm{\Omega }\mathrm{cm}$. An electron mobility as high as $38{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ is measured for a high free carrier density of $6.5\times {10}^{18}{\mathrm{cm}}^{-3}$. The crystallization in the $\alpha$-phase was confirmed by x-ray diffraction measurements. Further, a strong influence of the growth temperature on the zirconium incorporation is observed, which can be explained by the increased desorption of volatile ${\mathrm{Ga}}_2{\mathrm{O}}_3$ suboxides at high growth temperatures. Depth-resolved x-ray photoelectron spectroscopy measurements were employed to investigate the doping profile in the thin films. They reveal a strongly depth-dependent incorporation of the zirconium, with a decreased incorporation towards the surface. First Schottky barrier diodes on zirconium-doped $\alpha$-${\mathrm{Ga}}_2{\mathrm{O}}_3$ thin films with rectification ratios as high as 8.5 orders of magnitude at $\pm 3\mathrm{V}$ are presented.

We report on the achievement of a reduced time difference in a time scale with respect to Coordinated Universal Time (UTC) by steering a hydrogen-maser-based time scale with a near-continuously operating optical lattice clock. The time scale is generated in a postprocessing analysis for 230 days using a hydrogen maser with its fractional frequency stability limited by a flicker floor of $2\times {10}^{-15}$ and an $\mathrm{Yb}$ optical lattice clock operated with an uptime of 81.6%. During the 230-day period, the root-mean-square time difference of our time scale with respect to UTC is 0.52 ns, which is a better performance than those of time scales steered by microwave fountain clocks, which exhibit root-mean-square differences from 0.99 to 1.6 ns. With the high uptime achieved by the $\mathrm{Yb}$ optical lattice clock, our simulation results indicate the potential for generating a state-of-the-art time scale with a time difference of $<0.1$ ns over a month using a better hydrogen maser reaching the mid-${10}^{-16}$ stability level. This work demonstrates that the use of an optical clock with a high uptime enhances the stability of a time scale.

We demonstrate continuous Pound-Drever-Hall (PDH) nondestructive monitoring of the electron spin polarization of an atomic vapor in a microfabricated vapor cell within an optical resonator. The two-chamber silicon and glass cell contains ${}^{87}$Rb and 1.3 amg of ${\mathrm{N}}_2$ buffer gas, and is placed within a planar optical resonator formed by two mirrors with dichroic dielectric coatings to resonantly enhance the coupling to phase-modulated probe light near the $D_2$ line at 780 nm. We describe the theory of signal generation in this system, including the spin-dependent complex refractive index, cavity optical transfer functions, and PDH signal response to spin polarization. We observe cavity transmission and PDH signals across approximately 200 GHz of detuning around the atomic resonance line. By resonant optical pumping on the 795-nm $D_1$ line, we observe spin-dependent cavity line shifts, in good agreement with theory. We use the saturation of the line shift versus optical pumping power to calibrate the number density and efficiency of the optical pumping. In the unresolved sideband regime, we observe quantum noise limited PDH readout of the spin polarization density, with a flat noise floor of 9×${10}^9{\text{spins cm}}^{-3}{\text{Hz}}^{-1/2}$ for frequencies above 700 Hz. We note possible extensions of the technique.

We introduce a feasible scheme to produce high-rate long-distance entanglement that uses hybrid entanglement between continuous variables (CVs) and discrete variables (DVs). We show that hybrid entanglement can effectively remove the experimental limitations of existing CV and DV systems to produce long-range entanglement. We benchmark the resulting DV entangled states using an entanglement-based-quantum-key-distribution protocol. We show, using hybrid entangled states, that entanglement-based quantum key distribution is possible with standard telecommunication fibers for 300 km. The key idea is the use of the CV part, which can be adjusted to be robust regarding photon losses, for increasing the transmission distance, and the use of the DV part for achieving high secure key rates. Our results show that hybrid entangled states provide a clear advantage for practical generation of long-distance and high-rate entanglement that may lead to further applications in quantum information processing.

The coupling of ferromagnetic and ferroelectric materials has sparked great interest in the field of spintronics due to nonvolatile electrical magnetic control. In this work, we propose two-dimensional multiferroic ${\text{MnSe}}_2/{\text{In}}_2{\text{Se}}_3$ van der Waals (vdW) heterostructure to investigate the magnetoelectric coupling. The electronic structure, magnetic anisotropy, magnetic phase transition, and transport properties were investigated by employing the first-principles calculations in combination with the nonequilibrium Green’s function method. The results reveal that polarization reversal not only can effectively tune the Schottky-to-Ohmic contact but also reorients the magnetic easy axis. In addition, Curie temperature ($T_c$) was predicted based on the Heisenberg model and Monte Carlo simulations, and the competition between interfacial charge injection and lattice mismatch determines the $T_c$ of ${\text{MnSe}}_2/{\text{In}}_2{\text{Se}}_3$ heterostructure. Furthermore, we constructed the vdW ${\text{MnSe}}_2/{\text{In}}_2{\text{Se}}_3$-based magnetic-tunnel-junction and ferroelectric-tunnel-junction nanodevice, which exhibits high tunneling magnetoresistance of up to $1.805\times {10}^3\mathrm{\%}$ and a spin-filter efficiency of up to 98.5%. Our findings demonstrate the significant potentials of multiferroic ${\text{MnSe}}_2/{\text{In}}_2{\text{Se}}_3$ vdW heterostructures in designing a next-generation spintronic and nonvolatile memory device.

Superscattering is a unique wave phenomenon that allows subwavelength objects to produce a large scattering cross section, surpassing the fundamental single-channel limit. This effect has been extensively studied in many wave systems, such as electromagnetic waves, water surface waves, and airborne acoustics. However, in the context of underwater acoustics, achieving superscattering with a single material has remained unexplored due to complex acoustic-solid interactions. Here, we have inversely designed a simple yet efficient structure to achieve the superscattering of ultrasound in water. Both numerical simulations and experimental results show that the proposed superscatterer exhibits significantly stronger ultrasound backscattering compared with a bare rigid cylinder. Furthermore, we construct a superscattering chain barrier. It is able to enhance ultrasound insulation while maintaining water permeability. This chain barrier is demonstrated to be robust for ultrasound with a wide range of incident angles. The results from this study are expected to benefit various fields of underwater acoustics, particularly in marine detection and sea-life protection.

We present a sensitive diamond quantum sensor with a magnetic field sensitivity of $9.4\pm 0.1\mathrm{pT}/\sqrt{\mathrm{Hz}}$ in a near-dc frequency range of 5 to 100 Hz. This sensor is based on the continuous-wave optically detected magnetic resonance of an ensemble of nitrogen-vacancy centers along the [111] direction in a diamond (111) single crystal. The long $T_2^{\ast }\sim 2\text{μ}\mathrm{s}$ in our diamond and the reduced intensity noise in laser-induced fluorescence result in remarkable sensitivity among diamond quantum sensors. Based on an Allan-deviation analysis, we demonstrate that a subpicotesla field of 0.3 pT is detectable by interrogating the magnetic field for a few thousand seconds. The sensor head is compatible with various practical applications and allows a minimum measurement distance of about 1 mm from the sensing region. The proposed sensor facilitates the practical application of diamond quantum sensors. The sensitivity presented is realized without a magnetic flux concentrator, so that a sensitivity of tens of $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ can be achievable by using a flux concentrator.

Anti-ambipolar transistors (AATs) are a promising candidate for multivalued logic devices, which are vital for improving the device density and data-handling capabilities of nanoelectronics. Compared with most AATs with Λ-shaped transport characteristics, the emerging four-logic-state bi-AATs have a stronger capability for exponentially increasing the integration density. Here, we demonstrate an alternative strategy to achieve bi-anti-ambipolar transport by using the intrinsic electronic properties of two-dimensional (2D) materials. In detail, by breaking symmetry in edge-sharing octahedra, 2D X${\mathrm{PS}}_3$ (X = $\mathrm{Al},\mathrm{Ga},\mathrm{In},\mathrm{Tl}$) materials exhibit isolated band structures with subgap states near the Fermi level. More importantly, this special electronic feature inspires the design of double subgap tunnel field-effect transistors (TFETs) for realizing bi-anti-ambipolar transport. Through quantum transport simulations, we observe M-shaped I-V curves in the 2D ${\mathrm{InPS}}_3$ TFET, verifying the feasibility of the device concept. This work broadens the horizon for the development of bi-anti-ambipolar devices in the forthcoming era of big data.

The task of sensing the presence of a target object using a weak light source is challenging when the object is embedded in a noisy environment. One possibility is to use quantum illumination to do this, as it can outperform classical illumination in determining the object presence and range. This advantage persists even when both classical and quantum illumination are restricted to identical suboptimal object-detection measurements based on nonsimultaneous, phase-insensitive coincidence counts. Motivated by realistic experimental protocols, we present a theoretical framework for analyzing coincident multishot data with simple detectors. This approach allows for the often-overlooked noncoincidence data to be included, as well as providing a calibration-free threshold for inferring an object’s presence and range, enabling a fair comparison between different detection regimes. Our results quantify the advantage of quantum over classical illumination when performing target discrimination in a noisy thermal environment, including estimating the number of shots required to detect a target with a given confidence level.

Eddy currents in a superconductor shield the magnetic field in its interior and are responsible for the formation of a magnetic stray field outside of the superconducting structure. The stray field can be controlled by the external magnetic field and affect the magnetization dynamics in the magnetic system placed in its range. In the case of a hybrid system consisting of a superconducting strip placed over a magnetic layer, we theoretically predict the confinement of spin waves in the well of the static stray field. The number of bound states and their frequencies can be controlled by an external magnetic field. We present the results of semianalytical calculations complemented by numerical modeling.