Shortcut to adiabatic passage (STAP), initially proposed to accelerate adiabatic quantum-state transfer, has been widely explored and applied in quantum optics and integrated optics. Here we bring STAP into the field of acoustics to design compact couplers and functional metamaterial. The space-varying coupling strengths of acoustic waveguides (WGs) are tailored by means of dressed states in a three-level system, accounting for the desirable acoustic energy transfer among three WGs with short length. We show that the acoustic coupler has a one-way feature when loss is introduced into the intermediate WG. More uniquely, when the propagation of acoustic wave is designed to mimic a Hadamard transformation, an acoustic metamaterial can be constructed by arraying several couplers, possessing the beam-splitting function and unidirectional, broadband performances. Our work bridges STAP and the acoustic coupler as well as metamaterial, which may have profound impacts on exploring quantum technologies for promoting advanced acoustic devices.

We theoretically study the behavior of the critical current of a thermally biased tunnel Josephson junction with a particular design, in which the electrodes of the junction are enclosed in two different superconducting loops pierced by independent magnetic fluxes. In this setup, the superconducting gaps can be modified independently through the magnetic fluxes threading the loops. We investigate the response of the device as a function of the magnetic fluxes, by changing the asymmetry parameter, i.e., the ratio between the zero-temperature superconducting gaps $\delta ={\mathrm{\Delta }}_{10}/{\mathrm{\Delta }}_{20}$ and the temperatures of the two rings. We show a magnetically controllable steplike response of the critical current, which emerges even in a symmetric junction, $\delta =1$. Finally, we discuss the optimal working conditions and the high response of the critical current to small changes in the magnetic flux, reporting good performance of a magnetic flux-to-critical current transducer, with a high transfer function that depends on the operating point, the temperature gradient, and the quality of the junction.

Atomic spin sensors offer precision measurements using compact microfabricated packages, placing them in a competitive position for both market and research applications. The performance of these sensors, such as the dynamic range, may be enhanced through magnetic field control. In this work, we discuss the design of miniature coils for three-dimensional localized field control by direct placement around the sensor, as a flexible and compact alternative to global approaches used previously. Coils are designed on biplanar surfaces using a stream-function approach and then fabricated using standard printed-circuit techniques. Application to a laboratory-scale optically pumped magnetometer of sensitivity approximately $20\mathrm{fT}/\sqrt{\mathrm{Hz}}$ is shown. We also demonstrate the performance of a coil set measuring $7\times 17\times 17{\mathrm{mm}}^3$ that is optimized specifically for magnetoencephalography, where multiple sensors are operated in close proximity to one another. Characterization of the field profile using ${}^{87}$$\mathrm{Rb}$ free-induction spectroscopy and other techniques show $>96\mathrm{\%}$ field homogeneity over the target volume of a MEMS vapor cell and a compact stray-field contour of approximately $1\mathrm{\%}$ at 20 mm from the center of the cell.

Phononic crystals (PnC) are spatially periodic materials with band gaps that form by Bragg scattering of elastic waves. Within the frequency range of a band gap, wave propagation is not admitted. A long-standing limitation of this class of materials is that the wavelength for band-gap formation must be on the order of the unit-cell size. This restricts the presence of band gaps to relatively high frequencies for a given lattice spacing. Locally resonant metamaterials, on the other hand, enable the opening of low-frequency, subwavelength band gaps through resonance hybridization. However, their band gaps are characteristically narrow and require large or massive local resonators to form. Here, we break both limitations using beam-based PnCs by (1) locking the rotation degree of freedom at the edges of the primitive unit cell, and (2) coiling the PnC by applying full beam-axis rotations at the locked locations. These respective kinematic and geometric transformations convert a conventional beam PnC from its extended form with a nominal lattice constant to an extremely compact coiled configuration with a greatly reduced lattice constant. With the periodic rotational locking, the band gaps remain intact and are still large, and in fact increase noticeably in size. With the subsequent coiling, the band gaps remain based on Bragg scattering and are quantitatively conserved except now appearing at lower frequencies as dictated by the ratio of the extended-to-coiled lattice constants. This ratio defines a coiling factor, which is a measure of the reduction in the PnC unit-cell length in the direction of wave transmission while maintaining the band structure of its original extended form except for the favorable changes induced by the periodic rotational locking. A coiling factor of $\beta$ lowers, by construction, the location of the normalized central frequency of any given band gap by a factor of $\beta$. The only limitation is the need for lateral space to accommodate the coiling of the beam segments. The vibration behavior of a finite version of the coiled structure is experimentally tested demonstrating a matching band-gap response, despite the reduction in length, to that obtained by finite-element analysis of the extended rotationally locked version. This concept creates effectively subwavelength Bragg band gaps. It clears the path for PnCs to serve in applications that are orders-of-magnitude smaller in scale than are currently possible, while featuring band gaps that are significantly larger than those generated by locally resonant metamaterials.

Elastic waves traveling through polycrystalline ice Ih can experience distortion due to the transversely isotropic structure of its crystals. This can pose a challenge to nondestructive ultrasonic testing when ice is used as a coupling medium to transfer energy between an ultrasonic source and the solid to be inspected for the presence of damage. Here, it is shown that when ice is grown on a metallic solid using directional freezing techniques, it develops a coarse columnar grain structure, which causes the ultrasonic signals to vary greatly depending on which region of the ice volume is interrogated. On the other hand, if small ice particles are compacted around the solid and saturated with degassed liquid water before directional freezing, an equiaxed grain structure is obtained, which behaves as a homogeneous and isotropic medium. Furthermore, it is demonstrated that ultrasonic transmission through an ice-metal interface can be achieved regardless of the angle formed between the ultrasonic beam and the interface. Therefore, it is possible to overcome one of the fundamental limitations of conventional water coupling, which prevents transmission when the beam is not close to orthogonal to the interface due to the total reflection phenomenon. This property is useful to expand the scope of the application of ultrasonic testing to solids with complex geometries such as those obtained with additive manufacturing methods.

The developing frequency-comb spectral technologies have potential applications and prospects in the wide fields of cosmology, meteorology, and microwave measurement. Here, we demonstrate a Rydberg microwave-frequency-comb spectrometer via multiple-microwave field dressing, providing precise microwave measurement. The Rydberg microwave-frequency-comb spectrum provides a real-time and absolute-frequency measurement with a range of 125 MHz and gives the relative phase of a single-frequency microwave signal. The reported experiment helps real-time sensing of an unknown microwave signal over a wide range using Rydberg atoms, which are vital for Rydberg-atom-based microwave metrology.

Unlike ferromagnets, collinear antiferromagnets have two precession modes exhibiting opposite chirality, which enables the use of the polarization degree of freedom of magnons. In this study, we experimentally measure the polarization-selective spectra of magnetic resonance in perpendicularly magnetized synthetic antiferromagnets using a wideband crossed microstrip circuit. The magnetic resonances with right-handed and left-handed precession modes are directly detected, and theoretical analysis and numerical simulations explain the measurement results by considering the difference in the perpendicular magnetic anisotropy and damping constant between the top and bottom ferromagnetic layers. We also show that magnetic excitations with different polarization types can be excited under degeneracy between the two precession modes. Our work suggests that perpendicularly magnetized synthetic antiferromagnet structures provide an attractive platform for manipulating the polarization degree of freedom of magnons.

Long-distance spin transport through antiferromagnetic insulators (AFMIs) is a long-standing goal of spintronics research. Unlike conventional spintronics systems, monolayer graphene in the quantum Hall regime (QH) offers an unprecedented tuneability of spin-polarization and charge-carrier density in QH edge states. Here, using gate-controlled QH edges as spin-dependent injectors and detectors in an all-graphene electrical circuit, we demonstrate a selective tuning of ambipolar spin transport through graphene ν = 0 AFMIs. By modulating polarities of the excitation bias, magnetic fields, and charge carriers that host opposite chiralities, we show that the difference between spin chemical potentials of adjacent edge channels in the spin-injector region is crucial in tuning spin transport observed across graphene AFMI. We demonstrate that nonlocal response vanishes upon reversing directions of the co-propagating edge channels when the spin filters in our devices are no longer selective for a particular spin polarization. Our results establish a versatile set of methods to tune pure spin transport via an antiferromagnetic media and open a pathway to explore their applications for a broad field of antiferromagnetic spintronics research.

The nontrivial shape of colloidal particles creates complex elastic distortions and topological defects in liquid crystals and plays a key role in governing their electrophoretic propulsion through the medium. Here, we report experimental results on defects and the electrophoretic transport of anisometric (snowman-shaped) polystyrene particles subjected to an alternating electric field perpendicular to the director in a nematic liquid crystal. We demonstrate that the shape asymmetry gives rise to defect polymorphism by nucleating point or ring defects at multiple locations on the particle and controls the direction as well as the magnitude of the electrophoretic propulsion. Unlike spherical particles, quadrupolar anisometric particles can be transported in multiple directions in the plane perpendicular to the applied field. Our findings provide an alternative degree of freedom in translocating microparticles in liquid crystals for applications in microfluidics, controlled transport, and directed assembly.

We propose and verify a method for controlling the frequency dependence of the group delay of electromagnetic waves over a broad frequency range using the Brewster effect in single-layer metamaterials with finite thickness, here referred to as metafilms. When the reflectance of the metafilm vanishes regardless of the incident frequency, the group delay can be large near its resonance frequency while maintaining the transmittance close to unity regardless of the incident frequency. Furthermore, when several reflectionless metafilms are stacked together, the total group delay should be given as the sum of the individual group delays. In this study, we realize reflectionless metafilms by arranging the meta-atoms so that the Brewster effect occurs regardless of the incident frequency. We evaluate in numerical simulations and experiments the frequency dependence of the transmittance and of the group delay of a three-layer metamaterial composed of reflectionless metafilms with different resonance frequencies and find that the total transmittance and group delay of this metamaterial agree, respectively, with the product of the transmittances and the sum of the group delays of the constituent metafilms.

We propose the design of a vibrational energy-absorption device based on the concept of inertial amplification, by utilizing coupling between translational and rotational motions. A compact and lightweight device, with dimensions being only 10–20 cm and weighing less than 1 kg, can achieve ultralow-frequency resonance response at seismic frequency range, i.e., 0.5–5 Hz. Resonators that can respond at such a low-frequency range are usually bulky structures on the civil-engineering scale; our compact design offers flexibility and options for practical applications. Fabricated functional prototypes verify the very large inertial-amplification factor, up to 137, through vibrational characterizations. Experimentally measured data are consistent with our analytical modeling of the inertial-amplification mechanism. Furthermore, we propose a structurally refined device configuration and demonstrate, through simulations, its capability of vibrational total absorption with a comparatively broadband working frequency range. Our design can be easily adapted for resonance frequencies up to 100 Hz, via further miniaturization of the device dimension and lowering of the inertial-amplification factor. The inertial-amplified resonator represents an unconventional solution to the difficult problem of ultralow frequency vibration mitigation, with compact and lightweight devices that can fit into limited space.

We study mutual synchronization in double nanoconstriction-based spin Hall nano-oscillators (SHNOs) under weak in-plane magnetic fields (${\mu }_0{H}_{\mathrm{IP}}=30–40$ mT) and also investigate its angular dependence. We compare SHNOs with different nanoconstriction spacings of 300 and 900 nm. In all devices, mutual synchronization occurs below a certain critical angle, which is higher for the 300 nm spacing than for the 900 nm spacing, reflecting the stronger coupling at shorter distances. Alongside the synchronization, we observe a strong second harmonic consistent with predictions that the synchronization may be mediated by the propagation of second-harmonic spin waves. However, although Brillouin light scattering microscopy confirms the synchronization, it fails to detect any related increase of the second harmonic. Micromagnetic simulations instead explain the angular-dependent synchronization as predominantly due to magnetodipolar coupling between neighboring SHNOs.

Magnetic skyrmions are promising candidates for logic-in-memory applications, intrinsically merging high-density nonvolatile data storage with computing capabilities, owing to their nanoscale size, fast motion, and mutual repulsions. However, concepts proposed so far suffer from reliability issues as well as inefficient conversion of magnetic information to electrical signals. In this paper, we propose a logic-in-memory device, which exploits skyrmion confinement and channeling using anisotropy energy barriers to achieve reliable data storage and synchronous shift in racetracks combined with cascadable and reprogrammable logics relying purely on magnetic interactions. The device combines a racetrack shift register based on skyrmions confined in nanodots with full-adder (FA) gates. The designed FA is reprogrammable and cascadable and can also be used to perform simple logic operations such as and, or, not, nand, xor, and nxor. The monolithic design of the logic gate and the absence of any complex electrical contacts makes the device ideal for integration with conventional CMOS circuitry.

We propose a numerical technique for modeling quantum multimodal light scattering by a perfectly conducting body. Using the special quantization technique, we develop the quantum adaptation of the characteristic mode approach widely used in classical electrodynamics. The method is universal with respect to the body’s configuration, as well as its dimensions relative to the wavelength. Using this method and calculating the first- and second-order field correlation functions, we demonstrate how scattering affects quantum-statistical features of the field. As an example, we consider the scattering of two single-photon incident Gaussian beams on a cylinder with a circular cross section. We show that the scattering is accompanied by two-photon interference and demonstrates the Hong-Ou-Mandel effect. It is shown that the scattered two-photon field and its correlations manifest directive propagation, which is controllable by various means (angles of incidence, configuration of the body, relations between its dimensions and the wavelength). We expect that this method will be useful for designing quantum-optical devices.

We introduce a nonlinear photonic system that enables asymmetric localization and unidirectional transfer of an electromagnetic wave through the second-harmonic generation process. Our proposed scattering setup consists of a noncentrosymmetric nonlinear slab with nonlinear susceptibility ${\chi }^{(2)}$ placed to the left side of a one-dimensional periodic linear photonic crystal with an embedded defect. We engineered the linear lattice to allow the localization of a selected frequency $2{\omega }_{\star }$ while frequency ${\omega }_{\star }$ is in the gap. Thus in our proposed scattering setup, a left-incident coherent transverse electric wave with frequency ${\omega }_{\star }$ partially converts to frequency $2{\omega }_{\star }$ and becomes localized at the defect layer while the unconverted remaining field with frequency ${\omega }_{\star }$ exponentially decays throughout the lattice and gets reflected. For a right-incident wave with frequency ${\omega }_{\star }$ there will not be any frequency conversion and the incident wave gets fully reflected. Our proposed structure will find application in designing optical components such as optical sensors, switches, transistors, and logic elements.

We theoretically propose and experimentally demonstrate a parallel electromagnetically induced transparency (parallel EIT) cooling technique for ion crystals in the Paul trap. It breaks the stringent cooling requirements of the standard EIT cooling, thus allowing, in principle, to simultaneously cool the motional mode spectrum with an arbitrary range. Experimentally a large cooling range over 5 MHz is proved by using a single trapped ${}^{40}{\mathrm{Ca}}^{+}$ ion. We also observe simultaneous near-ground-state cooling for all motional modes of a 4-ion chain with the best average phonon number of about 0.2. For cooling a large number of modes, we only need to modulate the probe beam of the standard EIT cooling with several rf frequencies. This cooling scheme has no selectivity for the types of ions (e.g., ${}^{171}{\mathrm{Yb}}^{+}$, ${}^{40}{\mathrm{Ca}}^{+}$), therefore it would be a powerful tool for initialization of all kinds of operational trapped-ion quantum computers or simulators.