As society paves its way towards device miniaturization and precision medicine, microscale actuation and transport become increasingly prominent research fields with high impact in both technological and clinical contexts. In order to accomplish movement of micron-sized objects towards specific target sites, active biohybrid transport systems, such as motile living cells that act as smart biochemically powered microcarriers, have been suggested as an alternative to synthetic microrobots. Inspired by the motility of leukocytes, we propose the amoeboid crawling of eukaryotic cells as a promising mechanism for transport of micron-sized cargoes and present an in-depth study of this type of composite active matter. Its transport properties result from the interactions of an active element (cell) and a passive one (cargo) and reveal an optimal cargo size that enhances the locomotion of the load-carrying cells, even exceeding their motility in the absence of cargo. The experimental findings are rationalized in terms of a biohybrid active particle model that describes the emergent cell-cargo dynamics and enables us to derive the long-time diffusive transport of amoeboid microcarriers. As amoeboid locomotion is commonly observed for mammalian cells such as leukocytes, our results lay the foundations for the study of transport performance of other medically relevant cell types and for extending our findings to more advanced transport tasks in complex environments, such as tissues.

Recently, the ${\mathrm{La}\mathrm{Al}\mathrm{O}}_3/{\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ (LAO/STO) interface has been highlighted as a major platform for spintronics, and its fundamental control of spin properties, therefore, becomes a key issue for application of this system. Here, we present a study showing the modulation of magnetic two-dimensional electron gases (2DEGs) with simultaneously enhanced spin-orbit interaction at the interface of LAO/STO by inserting ${\mathrm{La}\mathrm{Co}\mathrm{O}}_3$ submonolayers. At first, transport experiments provide evidence that Kondo behavior can be well controlled below about 13 K with the interlayer $\mathrm{Co}$ ions contributing as scattering centers. In addition, the systematic variation of the anomalous Hall effect obtained with increasing fraction of interfacial $\mathrm{Co}$ concentration below 10 K reveals that the spin polarization of 2DEGs is enhanced via submonolayer insertion. Simultaneously, we also observe an enlarged spin-orbit interaction at the buffered LAO/STO interface, resulting in a remarkably strong field-orientation-dependent magnetoresistance. Such tailored LAO/STO interfaces could potentially contribute to stronger spin-to-charge conversion responses and spin-torque measurements. Our observations indicate the subunit-cell insertion of functional layers to be a suitable route to tailor spin, orbital, and lattice interactions of the interfacial 2DEG, which makes the LAO/STO system an intriguing platform for spintronic applications.

Phase measurement constitutes a key task in many fields of science, both in the classical and quantum regime. The higher precision of such measurement offers significant advances, and can also be utilized to achieve finer estimates for quantities such as distance, the gravitational constant, electromagnetic field amplitude, etc. Here we theoretically model the use of a quantum network, composed of a randomly coupled set of two-level systems, as a processing device for phase measurement. An incoming resource state carrying the phase information interacts with the quantum network, whose emission is trained to produce a desired output signal. We demonstrate phase-precision scaling following the standard quantum limit and Heisenberg limit. This can be achieved using quantum resource states such as NOON states or other entangled states, however, we also find that classically correlated mixtures of states are alone sufficient, provided that they exhibit quantum coherence. Our proposed setup does not require conditional measurements, and is compatible with many different types of coupling between the quantum network and the phase-encoding state, hence making it attractive to a wide range of possible physical implementations.

We propose how to engineer longitudinal coupling to accelerate the measurement of a qubit longitudinally coupled to a cavity, motivated by the concept of shortcuts to adiabaticity. Different modulations are inversely designed from inverse engineering, counter-diabatic driving, and genetic algorithm, for achieving optimally large values of the signal-to-noise ratio (SNR) at a nanosecond scale. By comparison, we demonstrate that our protocols outperform the usual periodic modulations on pointer state separation and SNR. Finally, we show a possible implementation considering state-of-the-art circuit quantum electrodynamics architecture, estimating the minimal time allowed for the measurement process.

Superconducting quantum computing is experiencing a tremendous growth. Although major milestones have already been achieved, useful quantum-computing applications are hindered by a variety of decoherence phenomena. Decoherence due to two-level systems (TLSs) hosted by amorphous dielectric materials is ubiquitous in planar superconducting devices. We use high-quality quasilumped-element resonators as quantum sensors to investigate TLS-induced loss and noise. We perform two-tone experiments with a probe and pump electric fields; the pump is applied at different power levels and detunings. We measure and analyze time series of the quality factor and resonance frequency for very long time periods, up to 1000 h. We additionally carry out simulations based on the TLS interacting model in the presence of a pump field. We find that loss and noise are reduced at medium and high power, matching the simulations, but not at low power.

Efforts to make the International System of Units (SI) more accessible have been growing since the global redefinition of the SI in 2019. Presently, the ohm is defined through the quantum Hall effect (QHE). However, quantum Hall devices require strong magnetic fields for a robust expression of the QHE. Magnetically doped topological insulators offer an opportunity to circumvent this limitation, as they require no magnetic field to provide a quantized resistance plateau via the quantum anomalous Hall effect (QAHE). Here, we detail experimental methodology and noise-analysis techniques for high-precision measurements of QAHE devices.

Composite optical systems can show compelling collective dynamics. For instance, the cooperative decay of quantum emitters into a common radiation mode can lead to super-radiance, where the emission rate of the ensemble is larger than the sum of the rates of the individual emitters. Here, we report experimental evidence of super spontaneous four-wave mixing, an analogous effect for the generation of photon pairs in a parametric nonlinear process on an integrated photonic device. We study this phenomenon in an array of microring resonators on a silicon photonic chip coupled to bus waveguides. We measure a cooperative pair-generation rate that always exceeds the incoherent sum of the rates of the individual resonators. We investigate the physical mechanisms underlying this collective behavior, clarify the impact of loss, and address the aspects of fundamental and technological relevance of our results.

This paper presents a theoretical and experimental investigation into the electrostatic coupling mechanism between different nonlinear modes inside a single resonator. Nonlinear intermodal coupling allows an arbitrary mode to be used as a modulator for the resonance of the coupled mode, presenting an efficient method to tune the frequency of a specific vibration mode. Here, a capacitive micromechanical resonator is developed, in which different modes exhibit different nonlinear characteristics. Inside this resonator, interactions between different nonlinear modes induced by electrostatic fields are observed and accurately modeled. It demonstrates that resonance modulation control can be achieved by activating the coupled modes based on the dispersive parametric coupling effect. Meanwhile, the resonance modulation is jointly determined by coupled modes, providing a theoretical basis and approach for modal manipulation technology. The dispersive coupling between intrinsic modes enables the probe resonance to be tuned by nearly 100 times its bandwidth, and its range and polarity can also be controlled by selecting the resonance of the pump mode. It is proven that resonance modulation control induced by the modal coupling effect can efficiently tune the resonator’s resonance frequency over a wide range, which presents a promising voltage-frequency transduction scheme with high sensitivity and low noise for the precision instrument. Its pull range exhibits a great potential of more than 20% as a voltage-controlled oscillator and can be customized to satisfy different requirements, paving the way toward advanced mechanics.

We demonstrate highly efficient control of antiferromagnetic (AFM) magnon spins by the interfacial exchange interaction in heterostructures of ferrimagnetic yttrium iron garnet (YIG) and AFM ${\mathrm{Cr}}_2{\mathrm{O}}_3$. At low temperatures, ${\mathrm{Cr}}_2{\mathrm{O}}_3$ is antiferromagnetically ordered. The interfacial exchange interaction exerted by YIG lifts the degeneracy between the AFM magnon modes in ${\mathrm{Cr}}_2{\mathrm{O}}_3$, resulting in a net spin polarization and a spin current dominated by left-handed magnons, even at zero magnetic field, which is detected by the spin Seebeck effect with a 5-nm-thick $\mathrm{Pt}$ film. In the AFM magnon-dominated region, even if the magnetic field is not sufficiently strong to induce the spin-flop transition in ${\mathrm{Cr}}_2{\mathrm{O}}_3$, the total spin Seebeck signal polarity flips when the YIG magnetization switches. It clearly indicates that the ${\mathrm{Cr}}_2{\mathrm{O}}_3$ magnon polarization is controlled by YIG magnetization through the interfacial exchange interaction. The demonstration of the efficient control of AFM magnon polarization opens a pathway to manipulate AFM magnon quantum states using FM-AFM heterostructures.

We study the entanglement and memristive properties of three coupled quantum memristors. We consider quantum memristors based on conductance-asymmetric superconducting quantum interference device architectures that are coupled via inductors. The three quantum memristors are arranged in two different geometries: linear and triangular coupling configurations. We obtain a variety of correlation measures, including bipartite entanglement and tripartite negativity. For identical quantum memristors, we find that entanglement and memristivity follow the same behavior for the triangular case and the opposite one in the linear case. Finally, we study the multipartite correlations with the tripartite negativity and entanglement monogamy relations, showing that our system has genuine tripartite entanglement. Our results show that quantum correlations in multipartite memristive systems have a nontrivial role and can be used to design quantum memristor arrays for quantum neural networks and neuromorphic quantum computing architectures.

Dynamically modulating the infrared emissivity of materials is of great importance in various applications (e.g., thermal camouflage and radiative cooling). Even though graphene-based materials (such as multilayer graphene, MLG) have shown great potential in active control of emissivity, the device lifetime is rather short, while low-cost large-scale production is difficult to achieve. Herein, graphene aerogels (GAs) with high porosity are prepared by a simple hydrothermal method, and used as electrode in an infrared emissivity modulator with a sandwiched structure. It is demonstrated that the emissivity of GA can be tuned through ion intercalation by electrostatic gating. The modulation depth of GA is comparable to that of MLG, but device lifetime is much longer. This is likely due to the porous structure of GA formed by a continuous three-dimensional MLG network, which makes it easier for ion transport, while allowing effective charge transfer from anions adsorbed on or intercalated into MLG to carbons. Due to a change in surface roughness of GA upon compressing, the emissivity of GA can be further tuned by compressive strain, which provides additional freedom in control of emissivity. The observations offer a promising avenue for the preparation of large-scale emissivity modulators at low cost, which is beneficial for practical applications.

Recently, there have been many developments in domain-wall electronics, such as racetrack memory and domain-wall logic. Here, we show that some of the principles of the control of ferromagnetic and ferroelectric domain walls can be applied to graphene kinks and antikinks, which are topological states of buckled graphene membranes. Using molecular-dynamics simulations, we demonstrate the good properties of graphene kinks for application in a racetracklike memory. Specifically, it is shown that in a sawtooth (ratchetlike) potential, graphene kinks and antikinks are locked into discrete positions on the membrane, and their force-induced unidirectional motion resembles the operation of a digital shift register.

Pentamode material (PM) possesses great potential in underwater acoustic metamaterial device applications due to its broadband and solid-state merits. Previously proposed PM devices are all designed with single materials, where the additional weights for mass adjustment are connected directly to the struts for modulus adjustment. The coupling effects between them severely restrict available fabrication techniques and the realizable range of physical properties of PM devices. A multiphase PM configuration, the additional weights of which are bonded to the struts with interconnecting materials, is proposed, and a waterlike multiphase PM device based on the proposed configuration is developed to assess the validity of the multiphase PM configuration. It is revealed from both simulation and experimental results that the acoustic properties of the proposed multiphase PM device mimics water within the simulation frequency range of 3–24 kHz. The fabrication cost of the proposed multiphase PM device is reduced by 80%, and the duration is only 1/15 when compared to that of a single-phase PM device. Additionally, the multiphase PM has great advantages over single-phase PM for aspects such as withstanding higher hydrostatic pressure due to much more uniform stress distribution and broadening the realizable range of physical properties of PM devices significantly.

We propose the encoding of memristive quantum dynamics on a digital quantum computer. Using a set of auxiliary qubits, we simulate an effective non-Markovian environment inspired by a collisional model, reproducing memristive features between expectation values of different operators in a single qubit. We numerically test our proposal in an IBM quantum simulator with 32 qubits, obtaining a pinched hysteresis curve that characterizes our quantum memristor model. Furthermore, we extend our method to the case of two coupled quantum memristors, opening the door to the study of neuromorphic quantum computing in the current noisy devices.

The magnetocaloric effect of a given material is typically assessed through indirect estimates of the isothermal magnetic entropy change, $\mathrm{\Delta }{S}_M$. While estimating the adiabatic temperature difference, $\mathrm{\Delta }{T}_{\mathrm{ad}}$, is more relevant from the standpoint of refrigeration device engineering, this requires specialized experimental setups. We here present an approach to directly measure $\mathrm{\Delta }{T}_{\mathrm{ad}}$ through time-dependent magnetometry in a commercial superconducting quantum interference device (SQUID) device. We use as reference material gadolinium under a 20-kOe field change, and compare our results with those of the literature. Under nonadiabatic experimental conditions, a remarkably similar $\mathrm{\Delta }{T}_{\mathrm{ad}}(T)$ curve profile is obtained; however, its peak amplitude is underestimated. With a simple compensation methodology we are able to further approximate the profile of the $\mathrm{\Delta }{T}_{\mathrm{ad}}(T)$ curve obtaining the peak amplitude, the maximizing temperature, and the FWHM within relative errors of $-4\mathrm{\%}$, $-0.7\mathrm{\%}$, and 11%, respectively. Our reported approach makes the measurement of both $\mathrm{\Delta }{S}_M(T)$ and $\mathrm{\Delta }{T}_{\mathrm{ad}}(T)$ possible with a single instrument, enabling accelerated progress towards new, competitive, and industry-ready materials.

We consider the magnonic properties of two dipolarly coupled magnetic stripes, both deposited on a normal conductive substrate with strong spin-orbit coupling. A charge current in the substrate acts on the adjacent magnets with spin-orbit torques, which result in magnonic damping or antidamping of the spin waves, and hence a gain-loss coupling of the two magnetic stripes. The whole setup is demonstrated to exhibit features typical for parity-time- ($PT$) symmetric systems. Phenomena are demonstrated that can be functionalized in magnonic devices, including reconfigurable magnonic diodes and logic devices. Alternative stripe designs and $PT$-symmetric, periodic, coupled magnonic textures are studied. Analytical and full numerical analysis identify the conditions for the appearance of exceptional points (EPs), where magnonic gain and loss are balanced and evidence nonreciprocal magnon propagation and enhanced magnon excitation around EPs. Furthermore, the dipolar coupling is shown to bring in a wave-vector-dependent $PT$-symmetric behavior. Proposing and simulating a $PT$-symmetric magnonic crystal, we show how EPs and hence associated phenomena can be steered to a particular wave vector in a gaped spectrum via material design. The phenomena offer additional tools for magnonic based communication and computational devices.

While nitrogen-vacancy ($\mathrm{N}$-$V^{-}$) centers have been extensively investigated in the context of spin-based quantum technologies, the spin-state readout is conventionally performed optically, which may limit miniaturization and scalability. Here, we report photoelectric readout of ground-state cross-relaxation features, which serves as a method for measuring electron-spin resonance spectra of nanoscale electronic environments and also for microwave-free sensing. As a proof of concept, by systematically tuning N-$V$ centers into resonance with the target electronic system, we extract the spectra for the P1 electronic spin bath in diamond. Such detection may enable probing optically inactive defects and the dynamics of local spin environment. We also demonstrate a magnetometer based on photoelectric detection of the ground-state level anticrossings (GSLACs), which exhibits a favorable detection efficiency as well as magnetic sensitivity. This approach may offer potential solutions for determining spin densities and characterizing local environment.

An exact theory is developed with the aim of assessing the properties of the harmonics spectrum of the dynamic magnetization originating from superparamagnetic nanoparticles submitted to a high-frequency driving field. The magnetization is assumed to be always close to equilibrium at the frequencies of interest, so that it can still be described by the anhysteretic Langevin function. The theory, valid for an extended range of values of physical properties and sizes of particles, is aimed at interpreting typical results of magnetic particle spectroscopy and imaging. The analytical framework is exploited to get a deeper knowledge of the spectral properties of nanoparticle magnetization and to assess the persistence of the superparamagnetic behavior at the operating frequencies. The spectral properties of the time-dependent Langevin function are analyzed in detail and compared with experimental results on polydisperse, immobilized nanoparticles. The system function usually exploited in magnetic particle imaging is calculated with precision as a function of both particle size and driving field’s amplitude.