Quantum entanglement represents an ideal resource to guarantee the security of random numbers employed in many scientific and cryptographic applications. However, entanglement-based certified random number generators are particularly challenging to implement. Here, we demonstrate a certified quantum random number generator based on momentum-polarization entangled single-photon states. The use of single-photon entanglement allows an attenuated laser source to be employed and a simple setup where only linear optical components are utilized. For the latter, a semi-device-independent modeling of the photonic quantum random number generator is developed, which certifies a minimum entropy of $(2.5\pm 0.5)\mathrm{\%}$, corresponding to a generation rate of 4.4 kHz. At the expenses of a higher level of trust in the system, the certified minimum entropy can be increased to $(30.1\pm 0.5)\mathrm{\%}$, implying a generation rate of 52.7 kHz. Our results show that a simple optical implementation combined with an accurate modeling provide an entanglement-based high-security quantum random number generator using imperfect devices.

We use phase-resolved imaging to directly study the nonlinear modification of the wavelength of spin waves propagating in 100-nm-thick in-plane magnetized yttrium iron garnet waveguides. We show that, by using moderate microwave power, one can realize spin waves with large amplitudes corresponding to precession angles in excess of 10° and nonlinear wavelength variation of up to 18% in this system. We also find that, at large precession angles, the propagation of spin waves is strongly affected by the onset of nonlinear damping, which results in a strong spatial dependence of the wavelength. This effect leads to spatially dependent controllability of the wavelength by the microwave power. Furthermore, it leads to the saturation of nonlinear spectral shift effects several micrometers away from the excitation point. These findings are important for the development of nonlinear integrated spin-wave signal-processing devices and can be used to optimize their characteristics.

The faithful distribution of entanglement over noisy channels is a vital prerequisite for many quantum technological applications. Quantum information can be encoded in different degrees of freedom (DOF) of photons, where each encoding comes with its own advantages and disadvantages with respect to noise resilience and practicality in manipulation. In this work, we experimentally implement a deterministic entanglement purification protocol that allows us to faithfully distribute entanglement in one DOF over a noisy channel and then remotely transfer it to another DOF for manipulation. In particular, we distribute robust energy-time entanglement and transfer it to polarization entanglement at the communicating parties. The remotely obtained polarization state is independent of the polarization noise during distribution and reaches fidelities to a Bell state of up to $97.6\mathrm{\%}$. Our scheme enables robust and efficient polarization entanglement distribution in the presence of arbitrary polarization noise, which is relevant for future large-scale quantum networks.

The moiré effect provides an interpretation for the steering of antennas that form beams through internal spatial interferences. We make an explicit connection between such antennas and the moiré effect, and use it to model six planar antennas that steer by scaling, rotating, or translating operations. Three of the antennas illustrate how to use moiré patterns to generate antenna designs.

Resistive random-access memory has attracted tremendous attention and numerous investigations as a promising next-generation nonvolatile memory device to address the physical limits of flash memory. Particularly, physically transient resistive switching memory is intensively researched for its degradable and environmentally friendly characteristics. Zinc oxide ($\mathrm{Zn}\mathrm{O}$), as a low-cost biocompatible and biodegradable material, has been widely used in the dielectric layer, yet many previous studies on $\mathrm{Zn}\mathrm{O}$-based memory devices show unsatisfactory switching properties. In this work, ${\mathrm{Mo}\mathrm{S}}_2$ quantum dots (QDs) are added between the $\mathrm{W}$ bottom electrode and $\mathrm{Zn}\mathrm{O}$ insulator by spin coating ($\mathrm{W}/{\mathrm{Mo}\mathrm{S}}_2$ QD$/\mathrm{Zn}\mathrm{O}/\mathrm{Ag}$) to improve its resistive switching behavior. The modified device exhibits distinctly better properties, including more-uniform switching parameters (low- and high-resistance states, $V_{\mathrm{set}}$, $V_{\mathrm{reset}}$), ultralow threshold voltages, and steady retention. Moreover, we transfer the device onto polyvinyl alcohol substrate, making it fully degradable, and it is completely dissolved in phosphate-buffered solution after 40 min. These results indicate that the ${\mathrm{Mo}\mathrm{S}}_2$ QD–optimized transient resistive switching memory shows great potential in green electronics, implantable biomedical devices, and secure information-storage applications.

An ultrahigh electric field induced by ionic liquid gating (ILG) can be employed to manipulate ferromagnetism with low Joule heating dissipation, showing great potential for spintronics applications. In ferromagnetic/heavy metal thin films, however, typical materials used in both layers are electron-carrier dominant, which significantly suppresses the ILG effect due to the short electrostatic screening length in metal. Here, we employ ${\mathrm{Mn}}_2\mathrm{Co}\mathrm{Al}$, a spin gapless semiconductor with hole carriers, as the ferromagnetic layer and investigate the ILG effect in $\mathrm{Mg}\mathrm{O}/{\mathrm{Mn}}_2\mathrm{CoAl/Pd}$ ultrathin films with perpendicular magnetic anisotropy. Reversible change of the magnetic anisotropy from the out-of-plane to the in-plane direction is achieved, induced by electrostatic charge accumulation. Moreover, ambipolar transport behavior has been observed and explained by a two-carrier model. Finally, we find that skew scattering is the mechanism of the anomalous Hall effect and can be enhanced at a positive gate voltage in our system. Our results strongly demonstrate that a significant ILG effect on magnetism can be easily achieved in two-carrier dominant ultrathin films.

The interaction of radiation with chiral molecular films is not macroscopically invariant under mirror reflections and, accordingly, chiro-optical effects exist which affect the spatial symmetry of the radiation profile and which almost exclusively show up in the near field due to the large mismatch between molecule size and wavelength size. Here we prove that the scattering of a mirror-symmetric pair of plane waves by a nanowire lying on a chiral nanofilm is not mirror-symmetric with an angular dissymmetry factor that can be as large as a few tenths. Due to evanescent coupling, the nanowire efficiently experiences molecular chirality which produces a spatially asymmetric near field so that the self-consistent unbalanced excitation of nanowire photonic modes with opposite angular momenta yields asymmetric far-field interference. In addition to enriching the physical understanding of mirror symmetry breaking in chiral nanophotonics, our results could suggest ultra-efficient schemes for enantiomeric discrimination which is essential in biological chemistry and pharmacology.

Voltage-controlled magnetic anisotropy (VCMA) is a low-energy alternative to manipulate the ferromagnetic state, which has been recently also considered in antiferromagnets (AFMs). Here, we theoretically demonstrate that VCMA can be used to excite linear and parametric resonant modes in easy-axis AFMs with perpendicular anisotropy, thus opening the way for an efficient electrical control of the Néel vector and for the detection of high-frequency dynamics. Our work leads to two key results: (i) VCMA parametric pumping experiences the so-called “exchange enhancement” of the coupling efficiency and, thus, is 1–2 orders of magnitude more efficient than microwave magnetic fields or spin-orbit torques, and (ii) it also allows for zero-field parametric resonance, which cannot be achieved by other parametric pumping mechanisms in AFMs with an out-of-plane easy axis. Therefore, we demonstrate that VCMA parametric pumping is the most promising method for coherent excitation and manipulation of AFM order in perpendicular easy-axis AFMs.

We explore the implementation of hybridly protected quantum operations combining the merits of geometry and holonomy, dynamical decoupling approach, and dephasing-free feature based on a simple and experimentally achievable spin model. The implementation of the quantum operations can be achieved in different physical systems with controllable parameters. The protected quantum operations are hence controllable and well suited for resolving various quantum-computation tasks, such as executing quantum error-correction codes or quantum error mitigation. Our scheme is based on an experimentally achievable Hamiltonian with reduced requirement of computational resources and thus, it brings us closer towards realizing protected quantum operations for resolving quantum-computation tasks in near-term quantum devices.

Scanning superconducting quantum interference device (SQUID) microscopy is a magnetic imaging technique combining high field sensitivity with nanometer-scale spatial resolution. Here, we demonstrate a scanning probe that combines the magnetic and thermal imaging provided by an on-tip SQUID with the tip-sample distance control and topographic contrast of a noncontact atomic force microscope (AFM). We pattern the nanometer-scale SQUID, including its weak-link Josephson junctions, via focused-ion-beam milling at the apex of a cantilever coated with Nb, yielding a sensor with an effective diameter of 365 nm, field sensitivity of $9.5\mathrm{nT}/\sqrt{\mathrm{Hz}}$, and thermal sensitivity of $620\mathrm{nK}/\sqrt{\mathrm{Hz}}$, operating in magnetic fields up to 1.0 T. The resulting SQUID-on-lever probe is a robust AFM-like scanning probe that expands the reach of sensitive nanometer-scale magnetic and thermal imaging beyond what is currently possible.

The modulation of millimeter-wave transmission through a silicon wafer upon photoexcitation is typically very inefficient for off-the-shelf low effective charge carrier lifetime wafers, typically requiring tens of kilowatts of photoexciting intensity to generate significant modulation. Here we demonstrate that increasing the light-matter interaction for the millimeter waves using diffractively coupled waveguide modes leads to an increase in photomodulation efficiency of greater than two orders of magnitude, while maintaining the switching speed, of the order of $10\mu \mathrm{s}$, of the bare wafer.

On-chip thermoelectric generation is of vital importance and is attracting wide attention as an option for implementing green microelectronics. We achieve temperature sensing and energy harvesting using the anomalous Nernst effect (ANE) in ${\mathrm{[IrMn/magnetic\; metal]}}_n$ multilayers, which can be used as on-chip temperature sensors and thermoelectric generators. An increase of 103% (1356%) in the voltage (power) generation coefficient is achieved by increasing the number of periods ($n$) from 1 to 7, due to the enhanced interfacial spin-orbit-coupled scattering. The voltage and power generation coefficients of an optimized ${\mathrm{[IrMn/NiFe]}}_5$ sample with geometric dimensions of $1800\mu \mathrm{m}\times 120\mu \mathrm{m}$ reach $1.3\mu \mathrm{V}{\mathrm{K}}^{-1}$ and $1.7\mathrm{pW}{\mathrm{K}}^{-2}$, respectively. Meanwhile, the exchange bias field introduced by Ir-Mn enables an ANE voltage and power output without an external field. Both features can advance the thermopower applications of ${\mathrm{[IrMn/magnetic\; metal]}}_n$ multilayers, especially the ${\mathrm{[IrMn/NiFe]}}_n$ system, for energy-efficient microelectronics.

As a secondary structure of DNA, DNA tetrahedra exhibit intriguing charge-transport phenomena and provide a promising platform for wide applications like biosensors, as shown in recent electrochemical experiments. Here, we study charge transport in a multiterminal DNA tetrahedron, finding that its charge-transport properties strongly depend upon the interplay of contact position, on-site energy disorder, and base-pair mismatch. Our results indicate that this multiterminal DNA tetrahedron behaves as a nanoscale charge splitter when the source is contacted at the top vertex. Besides, we find that the charge-transport efficiency is nearly independent of the contact position in the weak disorder regime, and is dramatically declined by the occurrence of a single base-pair mismatch between the source and the drain, in accordance with experimental results [J. Am. Chem. Soc. 134, 13148 (2012); Chem. Sci. 9, 979 (2018)]. By contrast, the charge-transport efficiency will be enhanced monotonically by shifting the source toward the drain in the strong disorder regime, and be increased when the base-pair mismatch takes place exactly at the contact position. In particular, when the source moves successively from the top vertex to the drain, the charge transport through the tetrahedral DNA device can be separated into three regimes, ranging from disorder-induced linear decrement of conductance to disorder-insensitive charge transport, and to disorder-enhanced charge transport. Finally, we predict that the DNA tetrahedron functions as a more efficient spin filter compared to double-stranded DNA and as a nanoscale spin splitter with opposite spin polarization observed at different drains. These results could be readily checked by electrochemical measurements and help for designing intriguing DNA tetrahedron-based molecular nanodevices.

We present an experimental study of local magnetic imaging in order to visualize the current flow in superconducting networks. We track the evolution of the spatial distribution of the current flow as the network is driven from fully superconducting to fully normal phases. Our results highlight the factors that contribute to the disordered flow in superconducting networks during their collapse, and demonstrate that the current is never uniformly distributed in the network. These results can assist the design and development of circuits based on superconductors and Josephson junctions.

In this work, we introduce an interconnected nano-optoelectronic spiking artificial neuron emitter-receiver system capable of operating at ultrafast rates (about $100\mathrm{ps}/$optical spike) and with low-energy consumption (< pJ/spike). The proposed system combines an excitable resonant tunneling diode (RTD) element exhibiting negative differential conductance, coupled to a nanoscale light source (forming a master node) or a photodetector (forming a receiver node). We study numerically the spiking dynamical responses and information propagation functionality of an interconnected master-receiver RTD node system. Using the key functionality of pulse thresholding and integration, we utilize a single node to classify sequential pulse patterns and perform convolutional functionality for image feature (edge) recognition. We also demonstrate an optically interconnected spiking neural network model for processing of spatiotemporal data at over 10 Gbit/s with high inference accuracy. Finally, we demonstrate an off-chip supervised learning approach utilizing spike-timing-dependent plasticity for the RTD-enabled photonic spiking neural network. These results demonstrate the potential and viability of RTD spiking nodes for low footprint, low-energy, high-speed optoelectronic realization of spike-based neuromorphic hardware.

An optical unitary converter (OUC) that can convert a set of $N$ mutually orthogonal optical modes into another set of arbitrary $N$ orthogonal modes is expected to be a key device in diverse applications, including optical communication, deep learning, and quantum computing. While various types of OUC have been demonstrated on photonic integration platforms, the sensitivity against a slight deviation in waveguide dimensions has been the crucial issue in scaling $N$. Here, we demonstrate that an OUC based on the concept of multiplane light conversion (MPLC) shows outstanding robustness against waveguide deviations. Moreover, it becomes more and more insensitive to fabrication errors as we increase $N$, which is in clear contrast to the conventional OUC architecture, composed of $2\times 2$ Mach-Zehnder interferometers. The physical origin behind this unique robustness and scalability is studied by considering a generalized OUC configuration. As a result, we reveal that the number of coupled modes in each stage plays an essential role in determining the sensitivity of the entire OUC. The maximal robustness is attained when all-to-all-coupled interferometers are employed, which are naturally implemented in a MPLC-based OUC.

Impurities in silicon are fundamental to a variety of modern nanoscale technologies working in both classical and quantum regimes of operation. The aggressive miniaturization of electronic devices has reduced their size to the nanometer scale, where the exact count and positioning of a few impurity atoms dictates their overall operation and performance. In the emerging area of quantum hardware development, single-impurity spins in silicon form excellent qubits and identifying their exact locations is important to engineer two-qubit interactions for high-fidelity quantum operations and the associated quantum control systems. This work reports a theoretical framework for the spatial metrology of single-impurity atoms in silicon with exact atomic precision for impurity depths approaching the bulk limit. The application of a carefully designed electric field pulls the impurity wave functions toward the surface, leading to spatially resolved scanning tunneling microscope images of electronic states exhibiting features that distinctly depend on the exact locations of the impurity atoms beneath the silicon surface. After verification of the developed metrology technique for individual atom positions, we train a machine-learning algorithm that can autonomously perform the metrology with high throughput in the presence of noise commensurate with experimental measurements. A future experimental implementation of the established capability for impurity-atom characterization is anticipated to play an important role in the design of a wide range of electronic and quantum devices.

The current autotuning approaches for quantum dot (QD) devices, while showing some success, lack an assessment of data reliability. This leads to unexpected failures when noisy or otherwise low-quality data is processed by an autonomous system. In this work, we propose a framework for robust autotuning of QD devices that combines a machine learning (ML) state classifier with a data quality control module. The data quality control module acts as a “gatekeeper” system, ensuring that only reliable data are processed by the state classifier. Lower data quality results in either device recalibration or termination. To train both ML systems, we enhance the QD simulation by incorporating synthetic noise typical of QD experiments. We confirm that the inclusion of synthetic noise in the training of the state classifier significantly improves the performance, resulting in an accuracy of $95.0(9)\mathrm{\%}$ when tested on experimental data. We then validate the functionality of the data quality control module by showing that the state classifier performance deteriorates with decreasing data quality, as expected. Our results establish a robust and flexible ML framework for autonomous tuning of noisy QD devices.