Search

Controllable coupling between the odd and even fundamental modes of an asymmetric half-wavelength superconducting coplanar waveguide resonator is demonstrated. The resonant frequency of the even mode Ω e could be tuned by an external magnetic field, while the resonant frequency of the odd mode Ω o is field independent. To realize the tunability of Ω e , the central conductor of the NbN-based resonator was galvanically coupled to an array of Al-based rf-SQUIDs (radio frequency superconducting quantum interferometer device). These rf-SQUIDs are placed in only one resonator gap, ensuring its strong asymmetry. By adjusting the appropriate external magnetic flux Φ , equal frequencies of both modes were obtained. At this resonant point Ω o (Φ) = Ω e (Φ) an avoided level crossing of the eigenfrequencies was observed, demonstrating the coupling between the odd and even fundamental modes. [ABSTRACT FROM AUTHOR]

We demonstrate control and readout of a superconducting artificial atom based on a transmon qubit using a compact lumped-element resonator. The resonator consists of a parallel-plate capacitor with a wire geometric inductor. The footprint of the resonators is about 200 × 200 μm2, which is similar to the standard transmon size and one or two orders of magnitude more compact in the occupied area compared to coplanar waveguide resonators. We observe coherent Rabi oscillations and obtain time-domain properties of the transmon. The work opens a door to miniaturize essential components of superconducting circuits and to further scale up quantum systems with superconducting transmons. [ABSTRACT FROM AUTHOR]

Fused silica has become an interesting alternative to silicon for millimeter-wave (mmWave) applications. Unfortunately, there are a few reports on the measurement of fused silica's permittivity above 110 GHz that use electrical rather than optical methods. Given that mmWave applications use electrical circuits, additional electrical data would be useful to industry. To test the feasibility of electrical methods, we applied on-wafer techniques based on coplanar waveguide transmission lines to measure the complex permittivity of fused silica to 325 GHz. Our approach used the multiline thru-reflect-line algorithm on the scattering parameter measurements of transmission lines. Our method combined these results with dc measurements of the resistivity of the metals, simulations of the coplanar waveguide cross section, and dimensional metrology. In short, our measurements do not show significant dielectric dispersion for fused silica up to 325 GHz. The resulting complex permittivity was ϵ r = 3.87 ± 0.03 and a loss tangent tan δ < 0.005 from 320 MHz to 325 GHz. To support our conclusions, we performed an uncertainty analysis considering relevant sources of uncertainty. In the broader context, these results show that fused silica is a suitable substrate for mmWave electronics where the loss tangent must be less than 0.005 up to 325 GHz. [ABSTRACT FROM AUTHOR]

The large physical size of superconducting qubits and their associated on-chip control structures presents a practical challenge toward building a large-scale quantum computer. In particular, transmons require a high-quality-factor shunting capacitance that is typically achieved by using a large coplanar capacitor. Other components, such as superconducting microwave resonators used for qubit state readout, are typically constructed from coplanar waveguides, which are millimeters in length. Here, we use compact superconducting through-silicon vias to realize lumped-element capacitors in both qubits and readout resonators to significantly reduce the on-chip footprint of both of these circuit elements. We measure two types of devices to show that through-silicon vias are of sufficient quality to be used as capacitive circuit elements and provide a significant reduction in size over existing approaches. [ABSTRACT FROM AUTHOR]

Terahertz pulses are nowadays commonly used in many areas of condensed matter physics to access material properties and explore transport phenomena at fast timescales. However, little work has been devoted to the full characterization of such pulses when confined in waveguides. In this work, we fabricate terahertz photoconductive switch detectors, located at various points along a coplanar waveguide, and sample the electrical pulses that pass by the detectors. Two different but consistent methods were developed to calibrate the pulse amplitude. Notably, we synchronize a commercial pulse generator with the laser in order to sample nanosecond-wide pulses with the photoswitch detectors, effectively turning the setup into an on-chip high-frequency sampling oscilloscope. Both methods give identical results on pulse current, voltage, and field amplitudes and enable an absolute characterization of the electrical pulse propagation along the waveguide. These techniques constitute a reliable tool to explore (non-linear) phenomena such as current or field induced magnetization switching or phase transitions, which take place at high THz intensities. [ABSTRACT FROM AUTHOR]

DyScO3 (DSO) is an attractive substrate on which to grow epitaxial thin films with extraordinary materials physics. However, its highly anisotropic permittivity makes some measurements exceedingly difficult: For instance, its permittivity tensor has not yet been fully characterized at millimeter-wave frequencies. While there are methods to characterize anisotropic permittivity at millimeter-wave frequencies, there are very few methods those are suitable for the small lateral dimensions that DyScO3 can be grown in. To overcome this lack in the material characterization, we tested an on-wafer method based on coplanar waveguides to measure the full anisotropic permittivity tensor from 0.1 to 110 GHz. We characterized two orthogonal sets of coplanar waveguides fabricated on each of two substrates with (001) and (110) crystallographic orientations to resolve the full permittivity tensor. To validate our measurements, we compared our results to data from dc parallel plate capacitors and THz time-domain spectroscopy. Our measurements fill the need for measurements of the permittivity of DyScO3, while the methodology, more generally, enables quantitative characterization of anisotropic dielectrics. [ABSTRACT FROM AUTHOR]

We present the use of a set of airbridges to trim the frequency of microwave coplanar-waveguide (CPW) resonators post-fabrication. This method is compatible with the fabrication steps of conventional CPW airbridges and crossovers and increases device yield by allowing compensation of design and fabrication uncertainty with 100 MHz range and 10 MHz resolution. We showcase two applications in circuit QED. The first is the elimination of frequency collisions between resonators intended to readout different transmons by frequency-division multiplexing. The second is frequency matching of readout and Purcell-filter resonator pairs. Combining this matching with transmon frequency trimming by laser annealing reliably achieves fast and high-fidelity readout across 17-transmon quantum processors. [ABSTRACT FROM AUTHOR]

Quantum hardware based on circuit quantum electrodynamics makes extensive use of airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Airbridges also provide an interconnect enabling transmission lines to cross. Traditional airbridge fabrication produces a curved profile by reflowing resist at elevated temperature prior to metallization. The elevated temperature can affect the coupling energy and even yield of pre-fabricated Josephson elements of superconducting qubits, tunable couplers, and resonators. We employ grayscale lithography to enable reflow and thereby reduce the peak temperature of our airbridge fabrication process from 200 to 150 °C and link this change to a substantial increase in the physical yield of transmon qubits with Josephson elements realized using Al-contacted InAs nanowires. [ABSTRACT FROM AUTHOR]

Nonreciprocal magnon propagation has recently become a highly potential approach of developing chip-embedded microwave isolators for advanced information processing. However, it is challenging to achieve large nonreciprocity in miniaturized magnetic thin-film devices because of the difficulty of distinguishing propagating surface spin waves along the opposite directions when the film thickness is small. In this work, we experimentally realize unidirectional microwave transduction with sub-micrometer-wavelength propagating magnons in a yttrium iron garnet (YIG) thin-film delay line. We achieve a non-decaying isolation of 30 dB with a broad field-tunable bandpass frequency range up to 14 GHz. The large isolation is due to the selection of chiral magnetostatic surface spin waves with the Oersted field generated from the coplanar waveguide antenna. Increasing the geometry ratio between the antenna width and YIG thickness drastically reduces the nonreciprocity and introduces additional magnon transmission bands. Our results pave the way for on-chip microwave isolation and tunable delay line with short-wavelength magnonic excitations. [ABSTRACT FROM AUTHOR]

A 400 MHz magnetoelectric (ME) Lamb wave antenna design to function in the medical implant communication service band is proposed. The antenna employs a heterostructure of piezoelectric and magnetostrictive membranes to acoustically excite standing shear bulk wave and radiate as a magnetic dipole. Multiphysics finite element analysis simulations are performed for transmission and reception modes. In these simulations, three aspects are investigated: piezoelectricity, micromagnetic precession, and magnetic dipole radiation. An experimental demonstration of the antenna is also conducted and shows mechanical resonance with a Q-factor of 500 and ME coupling. These results indicate that the design can be operated in zero-order antisymmetric (A0) mode as a tunable oscillator or sensor. This ME approach provides a solution to the miniaturization problem of traditional current-based implantable antennas. [ABSTRACT FROM AUTHOR]

Topological-material-based Josephson junctions have the potential to be used to host Majorana zero modes and to construct topological qubits. For operating the topological qubits at an appropriate timescale to avoid decoherence and quasiparticle poisoning, one would eventually go to the time domain and embed the topological qubits into quantum electrodynamic circuits. Here, we constructed a topological-insulator-nanowire-based transmon qubit and demonstrated its strong coupling to a coplanar waveguide resonator. The flux-tunable spectrum and Rabi oscillations with a qubit lifetime T 1 of ∼ 0.5 μ s were observed. Such a hybrid platform, containing topological materials and quantum electrodynamic circuits, can further be used to study the physical properties such as Majorana zero modes in topological quantum circuits. [ABSTRACT FROM AUTHOR]

Resonant elements play a vital role in tailoring of the radiation and scattering properties of devices, such as antennas and functional material platforms. We presently demonstrate a simple resonator that supports a multitude of scattering states. The resonator is a hybrid structure consisting of a finite-height dielectric cylinder integrated with a concentric impedance surface. Given its simple configuration, we apply the classical Lorentz–Mie theory to analyze its scattering properties analytically. Through a careful tuning of its geometry, the resonator is found to support enhanced and directive scattering states as well as the suppressed scattering states also known as anapole states. A prototype of the resonator has been built and tested at microwave frequencies. It utilizes water as the dielectric and a metallic tube with periodic slits as the impedance surface. Exploiting the flexibility of water, the design is easily reconfigured for different scattering responses: fully filled, the resonator is found to scatter predominantly in the forward direction, whereas an anapole state emerges with significant reduction of scattering when the resonator is partially filled with water. Consequently, the proposed resonator may be of great interest within the broad area of antenna design and functional material platforms, encompassing not only the obvious microwave frequencies but also the THz- and optical domain using high-permittivity dielectrics and graphene/nano-particle surfaces. [ABSTRACT FROM AUTHOR]

We acquire tantalum thin film in its α phase (α-Ta) using direct-current magnetron sputtering. According to x-ray diffraction results, 110-Ta is dominant. Quarter-wavelength coplanar waveguide resonators are fabricated with the α-Ta film and characterized at millikelvin in a dilution refrigerator. In the single photon regime, an intrinsic quality factor (Qi) up to 3 × 10 6 is obtained in these resonators. At high power, Qi rises to 6 × 10 6 . Moreover, we also fabricate an array with 7 × 7 lumped element resonators using the α-Ta film. The array shows excellent uniformity. At high power, Qis of all pixels exceed 1 × 10 6 . In the single photon regime, Qis of over 90% pixels exceed 1 × 10 6 . Superconducting quantum computing and ultrasensitive electromagnetic wave detectors will benefit a lot from devices based on the α-Ta film. [ABSTRACT FROM AUTHOR]

The large switchable ferroelectric polarization and lead-free composition of BiFeO3 make it a promising candidate as an active material in numerous applications, in particular, in micro-electro-mechanical systems (MEMS) when BiFeO3 is integrated in a thin film form on a silicon substrate. Here, 200-nm-thick Mn-doped BiFeO3 thin films have been epitaxially grown on a SrRuO3/SrTiO3/Si substrate and patterned into microcantilevers as prototype device structures for piezoelectric actuation. The devices demonstrate excellent ferroelectric response with a remanent polarization of 55 μC/cm2. The epitaxial BiFeO3 MEMS exhibit very high piezoelectric response with transverse piezoelectric coefficient d31 reaching 83 pm/V. The BiFeO3 cantilevers show larger electromechanical performance (the ratio of curvature/electric field) than that of state-of-art piezoelectric cantilevers, including well-known PZT (Pb(Zr,Ti)O3) and the hyper-active PMN–PT (Pb(Mg1/3Nb2/3)O3-PbTiO3). In addition, the piezoelectricity in BiFeO3 MEMS is found to depend on the ferroelectric polarization direction, which could originate from the flexoelectric effect and be exploited to further enhance the electromechanical performance of the devices. These results could potentially lead to a replacement of lead-based piezoelectrics by BiFeO3 in many microdevices. [ABSTRACT FROM AUTHOR]

The impact of Cubic Silicon Carbide (3C-SiC) transition layer on breakdown voltage and frequency performance of GaN high electron mobility transistors is investigated. A combination of distinct material and device characterizations techniques, including Raman spectroscopy, coplanar waveguides, electrical measurements, and Technology Computer-Aided Design (TCAD) simulations, are adopted to inspect the role of the 3C-SiC interlayer. Raman spectra reveal a good quality of the 3C-SiC layer, similar to the mono-crystalline 3C-SiC spectra. A relatively low transmission loss of ∼0.16 dB/mm at 40 GHz is measured for the device with 3C-SiC layer, rather than 2.1 dB/mm for the device without 3C-SiC. In addition, a soft breakdown voltage around 1530 V at 1 μA/mm is achieved, which is three times larger compared with that of the conventional device. The failure mechanism, related to carrier injection at the nucleation layer, is not observed in the structure with the 3C-SiC layer. Instead, TCAD simulations disclose a substantial improvement of the buffer/substrate interface through the suppression of an interface current path. [ABSTRACT FROM AUTHOR]

In superconducting quantum circuits, airbridges are critical for eliminating parasitic slotline modes of coplanar waveguide circuits and reducing crosstalks between direct current magnetic flux biases. Here, we present a technique for fabricating superconducting airbridges. With this technique, a single layer of photoresist is employed, and the gradient exposure process is used to define the profile of airbridges. In order to properly obtain the bridge profile, we design exposure dosage based on residual photoresist thickness and laser power calibrations. Compared with other airbridge fabrication techniques, the gradient exposure fabrication technique provides the ability to produce lossless superconducting airbridges with flexible size and, thus, is more suitable for large-scale superconducting quantum circuits. Furthermore, this method reduces the complexity of the fabrication process and provides a high fabrication yield. [ABSTRACT FROM AUTHOR]

Enhanced directional radiation is important for various applications such as lasers and antennas. However, almost all existing enhanced directional emitters rely on the use of materials or structures that provide multiple reflections, which are often bulky, lossy, and difficult to fabricate. Here, we theoretically propose and experimentally demonstrate acoustic enhanced directional radiation with topological interface states in a specially designed acoustic waveguide with subwavelength width and no additional structure for multiple reflections. This waveguide is an acoustic analog of the double Su–Schrieffer–Heeger chain, in which a topological bandgap can be created by opening degenerate points away from the boundary of the Brillouin zone. Topological interface states between two topologically different waveguides were experimentally observed. A leaky-wave design is proposed for acoustic enhanced directional radiation. This leaky-wave waveguide can improve the radiation resistance and efficiency of a point source, and the radiation direction is locked by the momentum of the degenerate points. Acoustic enhanced directional radiation with more than ten times energy enhancement is observed in the experiment. The proposed strategy shows potential in the subwavelength wave manipulation and can be applied to acoustic communication, nondestructive evaluation, and biomedical imaging. [ABSTRACT FROM AUTHOR]

Antennas with omnidirectional radiation of electromagnetic wave have wide applications in sensing, positioning, and wireless communications. Here, we investigate the potentials of using epsilon-near-zero (ENZ) metamaterial to realize omnidirectional radiation with high degrees of freedom. We propose an omnidirectional antenna based on an ENZ cavity integrated in printed circuits board (PCB). By taking advantage of ENZ behavior, the ENZ antenna can decouple the radiation patterns and the operating frequency while maintaining the omnidirectional radiation characteristic. Based on the omnidirectional ENZ antenna element, a parallel-fed array is realized based on the low-cost PCB process. The integrated ENZ antenna array exhibits the capability of engineering the omnidirectional radiation flexibly, such as beam scanning and beam intensity control for practical applications. [ABSTRACT FROM AUTHOR]

Integrated circuits are building blocks in millimeter-wave handsets and base stations, requiring nonlinear characterization to optimize performance and energy efficiency. Today's sources use digital-to-analog converters to synthesize arbitrary electrical waveforms for nonlinear characterization, but this approach demands even faster integrated circuits to increase the bandwidth to millimeter-waves. Optically derived sources are a potential path to generate precise millimeter-waves and arbitrary waveforms using additive frequency synthesis. In this work, we demonstrate optically derived millimeter-waves up to 99.2 GHz with phase and amplitude control that could be locked to an optical reference. Our approach uses a 1550 nm electro-optic frequency comb with a terahertz of bandwidth. A programmable spectral filter selects two wavelengths from the optical comb, illuminating a modified uni-traveling carrier photodiode on a coplanar waveguide. We then tune the phase and amplitude by varying the optical phase and amplitude in the programmable spectral filter. The result of our work is electro-optically derived millimeter-waves at (24.8, 49.6, 74.4, and 99.2) GHz with phase and amplitude control, enabling arbitrary repetitive waveform generation. [ABSTRACT FROM AUTHOR]

We characterize low-loss electron-beam evaporated niobium thin films deposited under ultra-high vacuum conditions. Slow deposition yields films with a high superconducting transition temperature (9.20 ± 0.06 K) as well as a residual resistivity ratio of 4.8. We fabricate the films into coplanar waveguide resonators to extract the intrinsic loss due to the presence of two-level-system fluctuators using microwave measurements. For a coplanar waveguide resonator gap of 2 μ m , the films exhibit filling-factor-adjusted two-level-system loss tangents as low as 1.5 × 10 − 7 with single-photon regime internal quality factors in excess of one million after removing native surface oxides of the niobium. [ABSTRACT FROM AUTHOR]

Spin waves (SWs) in magnetic nanotubes have shown interesting nonreciprocal properties in their dispersion relation, group velocity, frequency linewidth, and attenuation lengths. The reported chiral effects are similar to those induced by the Dzyaloshinskii–Moriya interaction but originating from the dipole–dipole interaction. Here, we show that the isotropic-exchange interaction can also induce chiral effects in the SW transport; the so-called Berry phase of SWs. We demonstrate that with the application of magnetic fields, the nonreciprocity of the different SW modes can be tuned between the fully dipolar governed and the fully exchange governed cases, as they are directly related to the underlying equilibrium state. In the helical state, due to the combined action of the two effects, every single sign combination of the azimuthal and axial wave vectors leads to different dispersions, allowing for a very sophisticated tuning of the SW transport. A disentanglement of the dipole–dipole and exchange contributions so far was not reported for the SW transport in nanotubes. Furthermore, we propose a device based on coplanar waveguides that would allow to selectively measure the exchange or dipole induced SW nonreciprocities. In the context of magnonic applications, our results might encourage further developments in the emerging field of 3D magnonic devices using curved magnetic membranes. [ABSTRACT FROM AUTHOR]

We demonstrate that a periodic waveguide comprising of uniform lossless segments together with discrete gain and radiating elements supports exceptional points of degeneracy (EPDs). We provide analytical expressions for all possible conditions that guarantee the occurrence of an EPD, i.e., the coalescence of eigenvalues and eigenvectors. We show that EPDs are not only achieved using symmetric gain and radiation periodic loading, but they are also obtained using asymmetric gain and radiation loss conditions. We illustrate the characteristics of the degenerate electromagnetic modes, showing the dispersion diagram and discussing the tunability of the EPD frequency. We show a special condition, and we refer to it as a parity-time-glide symmetry, which leads to a degeneracy that is occurring at all frequencies of operation. The class of EPDs proposed in this work is very promising for many applications that incorporate discrete-distributed coherent sources and radiation loss elements; operating in the vicinity of such special degeneracy conditions leads to a potential performance enhancement in a variety of microwave and optical resonators, antennas, and devices and can be extended to a new class of active integrated antenna arrays and radiating laser arrays. [ABSTRACT FROM AUTHOR]

We introduce a superconducting coplanar waveguide, in the form of a ring resonator, as a quantum bus for circuit quantum electrodynamics (circuit QED). Due to its unique symmetry, the amplitude of the electromagnetic field inside is uniform along the resonator, which in principle leads to a location independent coupling between qubits and the resonator. For an experimental demonstration, we designed and fabricated a ring resonator capacitively coupled to two tunable Xmon superconducting qubits. We showed that nearly identical coupling was achieved between individual qubits and the resonator. In addition, the resonator was also used as a high quality quantum bus for generating Bell states between the qubits with a fidelity of F = 98.6 % , although an interference effect must be included for understanding the effective coupling between the two qubits. Our results suggest that ring resonators can be a useful addition to the toolbox of circuit QED. [ABSTRACT FROM AUTHOR]

The planar topological Hall effect (PTHE), appearing when the magnetic field tended to be along the current, is believed to result from the real-space Berry curvature of the spin spiral structure and has been experimentally observed in skyrmion-hosting materials. In this paper, we report an experimental observation of the PTHE in a hexagonal ferromagnetic Fe5Sn3 single crystal. With a current along the c axis of Fe5Sn3, the transverse resistivity curves exhibited obvious peaks near the saturation field as the magnetic field rotated to the current and appeared more obvious with increasing temperature, which was related to the noncoplanar spin structure in Fe5Sn3. This spin structure induced nonzero scalar spin chirality, which acted as fictitious magnetic fields to conduction electrons and contributed the additional transverse signal. These findings deepen the understanding of the interaction between conduction electrons and complex magnetic structures and are instructive for the design of next-generation spintronic devices. [ABSTRACT FROM AUTHOR]

This document is an erratum for a letter published in the journal Applied Physics Letters. The erratum corrects an error in Equation (4) of the original letter, which was missing a factor of two. The correct equation is provided, along with an explanation of the error and the correct average energy in an RLC resonator. The authors acknowledge the error and thank Dr. Gergö Fülöp for bringing it to their attention, but state that the error does not affect the analysis or conclusions of the original paper. [Extracted from the article]

We characterize niobium nitride (NbN) λ / 2 coplanar waveguide resonators, which were fabricated from a 10-nm-thick film on silicon dioxide grown by sputter deposition. For films grown at 180 °C, we report a superconducting critical temperature of 7.4 K associated with a normal square resistance of 1 k Ω , leading to a kinetic inductance of 192 pH/◻. We fabricated resonators with a characteristic impedance up to 4.1 k Ω and internal quality factors Q i > 10 4 in the single photon regime at zero magnetic field. Moreover, in the many photon regime, the resonators present a high magnetic field resilience with Q i > 10 4 in a 6 T in-plane magnetic field and in a 300 mT out-of-plane magnetic field. These findings make such resonators a compelling choice for circuit quantum electrodynamics experiments involving quantum systems with small electric dipole moments operated in finite magnetic fields. [ABSTRACT FROM AUTHOR]

Energy conservation and battery life extension are key challenges for the next-generation hybrid electric vehicles. In particular, the temperature and electric currents in a storage battery need to be monitored simultaneously with ∼1 kHz signal bandwidth for optimum battery usage. Here we introduce a centimeter-scale portable quantum sensor head, consisting of a diamond substrate hosting an ensemble of nitrogen-vacancy (NV) color centers with a density of ∼3 × 1017 cm−3. One diamond surface is attached to a multi-mode fiber for simultaneous optical excitation and readout of the NV centers, while the other diamond surface is attached to a coplanar microwave guide for NV spin ground-state mixing. Signal bandwidth of 1 kHz was realized through time-domain multiplexing of the two-tone microwave frequency modulation at 20 kHz. Two microwave frequencies were locked to the two resonance points that were determined from the optically detected magnetic resonance spectrum. From the mean and the difference of the deviation from the two locked frequencies, the temperature and magnetic field were obtained simultaneously and independently, with sensitivities of 3.5 nT/Hz1/2 and 1.3 mK/Hz1/2, respectively. We also showed that our sensor reached a minimum detectable magnetic field of 5 pT by accumulating signals for over 10 000 s. [ABSTRACT FROM AUTHOR]

We investigate the performance of niobium nitride superconducting coplanar waveguide resonators toward realizing hybrid quantum devices with magnon-photon coupling. We find internal quality factors ∼ 20 000 at 20 mK base temperature, in zero magnetic field. We find that by reducing film thickness below 100 nm, an internal quality factor greater than 1000 can be maintained up to a parallel magnetic field of ∼ 1 T and a perpendicular magnetic field of ∼ 100 mT. We further demonstrate strong coupling of microwave photons in these resonators with magnons in chromium trichloride, a van der Waals antiferromagnet, which shows that these cavities serve as a good platform for studying magnon-photon coupling in 2D magnonics based hybrid quantum systems. We demonstrate strong magnon-photon coupling for both optical and acoustic magnon modes of an antiferromagnet. [ABSTRACT FROM AUTHOR]

We present a lab-on-chip technique to measure the very low losses in superconducting transmission lines at (sub-) mm wavelengths. The chips consist of a 100 nm-thick NbTiN Co-planar Waveguide (CPW) Fabry–Pérot (FP) resonator, coupled, on one side, to an antenna and, on the other side, to a Microwave Kinetic Inductance detector. Using a single frequency radiation source allows us to measure the frequency response of the FP around 350 GHz and deduce its losses. We show that the loss is dominated by radiation loss inside the CPW line that forms the FP and that it decreases with the decreasing linewidth and increasing kinetic inductance as expected. The results can be quantitatively understood using SONNET simulations. The lowest loss is observed for a CPW with a total width of 6 μ m and corresponds to a Q-factor of ≈ 15 000. [ABSTRACT FROM AUTHOR]

The rise in consumer data usage has increased the demand for higher data rates in telecommunication in both wireless and wired systems. In order to meet the demands for increased data rates for wired services, one possibility is to switch to higher frequencies, beyond the MHz-range frequencies typically used in digital subscriber line (DSL) services. In this work, we investigate the channel properties of a 200 GHz signal transmitted through a waveguide structure that is designed to approximately emulate the type of paired phone cable typically used for DSL transmissions. We report the attenuation characteristics of such a channel and explore the achievable data rates of a realistic vectored scenario that exploits the modal diversity of this multi-mode channel. We find that aggregate data rates on the order of terabits per second are feasible over short distances. [ABSTRACT FROM AUTHOR]

Surface plasmon polaritons have rapidly established themselves as a promising concept for molecular sensing, near-field nanoimaging, and transmission lines for emerging integrated ultracompact photonic circuits. In this letter, we demonstrate a highly compact surface plasmon polariton detector based on an axial metal-semiconductor-metal nanowire heterostructure device. Here, an in-coupled surface plasmon polariton propagates along an aluminum nanowire waveguide joined to a high index germanium segment, which effectively acts as a photoconductor at low bias. Based on this system, we experimentally verify surface plasmon propagation along monocrystalline Al nanowires as thin as 40 nm in diameters. Furthermore, the monolithic integration of plasmon generation, guiding, and detection enables us to examine the bending losses of kinked waveguides. These systematic investigations of ultrathin monocrystalline Al nanowires represent a general platform for the evaluation of nanoscale metal based waveguides for transmission lines of next generation high-speed ultracompact on-chip photonic circuits. [ABSTRACT FROM AUTHOR]

We report on fast tunability of an electromagnetic environment coupled to a superconducting coplanar waveguide resonator. Namely, we utilize a recently developed quantum-circuit refrigerator (QCR) to experimentally demonstrate a dynamic tunability in the total damping rate of the resonator up to almost two orders of magnitude. Based on the theory, it corresponds to a change in the internal damping rate by nearly four orders of magnitude. The control of the QCR is fully electrical, with the shortest implemented operation times in the range of 10 ns. This experiment constitutes a fast active reset of a superconducting quantum circuit. In the future, a similar scheme can potentially be used to initialize superconducting quantum bits. [ABSTRACT FROM AUTHOR]

Characterizing superconducting microwave resonators with highly dissipative elements is a technical challenge, but a requirement for implementing and understanding the operation of hybrid quantum devices involving dissipative elements, e.g., for thermal engineering and detection. We present experiments on λ/4 superconducting niobium coplanar waveguide resonators, terminating at the antinode by a dissipative copper microstrip via aluminum leads, such that the resonator response is difficult to measure in a typical microwave environment. By measuring the transmission both above and below the superconducting transition of aluminum, we are able to isolate the resonance. We then experimentally verify this method with copper microstrips of increasing thicknesses, from 50 nm to 150 nm, and measure quality factors in the range of 10–67 in a consistent way. [ABSTRACT FROM AUTHOR]

We present a hybrid system consisting of a superconducting coplanar waveguide resonator coupled to a nanomechanical string and a transmon qubit acting as a nonlinear circuit element. We perform spectroscopy for both the transmon qubit and the nanomechanical string. Measuring the ac-Stark shift on the transmon qubit and the electromechanically induced absorption on the string allows us to determine the average photon number in the microwave resonator in both the low and high power regimes. In this way, we measure photon numbers that are up to nine orders of magnitude apart. We find a quantitative agreement between the calibrations of photon numbers in the microwave resonator using the two methods. Our experiments demonstrate the combination of superconducting circuit quantum electrodynamics and nano-electromechanics on a single chip. [ABSTRACT FROM AUTHOR]

Topological Hall effect (THE) as one of spin-related effects originates from scalar spin chirality formed by non-coplanar spin structures, being a promising tool for probing the change of electron spin. Single-phase (022) Mn4N films with coplanar spin structures were prepared on unpoled ferroelectric [Pb(Mg1/3Nb2/3)O3]0.67-[PbTiO3]0.33 (PMN-PT) substrates. The transport properties of Mn4N/PMN-PT have been investigated. The decreased magnetization and anomalous resistivity imply that the spin states of Mn4N are influenced by ferroelectric polarization of the substrate. The observation of THE in the Mn4N/PMN-PT heterostructure strongly supports that the spin states of Mn4N are modified. After poling PMN-PT, the enhanced THE peak magnitude verifies that the spin states of Mn4N are tuned by ferroelectric polarization. This study provides a non-magnetic method for manipulation of spin states, which could avoid the external magnetic field perturbations. [ABSTRACT FROM AUTHOR]

Metasurfaces have shown unprecedented capabilities in manipulating the phase, intensity, and polarization of electromagnetic waves. The coupling efficiency of surface plasmon polaritons is overcome by polarization sensitivity metasurfaces, but they face challenges in the application of high-intensity-based SPPs confined to the surface of a metal. Based on spiral arrays combined with a concentric groove, we experimentally demonstrate the application-oriented and polarization-controlled terahertz superfocusing by emitting high-efficiency radially convergent SPPs into free space to form a focal spot beyond the diffraction limit. The full wave at half maximum of the focal spot is 0.38λ, and it shows tunable intensity (the overall intensity of the focused spot can be tuned) by controlling the polarization state of the incident waves. This work paves a way towards imaging, data storage, and lithography. [ABSTRACT FROM AUTHOR]

In this letter, a coplanar waveguide (CPW) filter based on spoof surface plasmon polaritons (SSPPs) in the microwave frequency band is proposed, which can achieve multi-band transmission by using periodic holes etched on the middle line of a CPW. Compared to the conventional SSPP designs, the proposed SSPP-based waveguide filter removes the gradual structure for the mode conversion. Simultaneously, the transmission efficiency of high-order modes is obviously improved by employing periodic holes etched on both the side grounds of the CPW. The physical mechanism of the proposed SSPP-based waveguide filter is explained with the aid of the dispersion curves and electric field distributions. Experimental results validate the proposed concept, and the measured results are in good agreement with the simulated ones, which indicates that the proposed SSPP-based waveguide filter can find potential applications in plasmonic integrated circuits at microwave frequencies. [ABSTRACT FROM AUTHOR]

The lateral thermal gradient of an yttrium iron garnet (YIG) film under microwave application in the cavity of the electron spin resonance system (ESR) was measured at room temperature by fabricating a Cu/Sb thermocouple onto it. To date, thermal transport in YIG films caused by the Damon-Eshbach mode (DEM)—the unidirectional spin-wave heat conveyer effect—was demonstrated only by the excitation using coplanar waveguides. Here, we show that the effect exists even under YIG excitation using the ESR cavity—a tool often employed to realize spin pumping. The temperature difference observed around the ferromagnetic resonance field under 4 mW microwave power peaked at 13 mK. The observed thermoelectric signal indicates the imbalance of the population between the DEMs that propagate near the top and bottom surfaces of the YIG film. We attribute the DEM population imbalance to different magnetic dampings near the top and bottom YIG surfaces. Additionally, the spin wave dynamics of the system were investigated using the micromagnetic simulations. The micromagnetic simulations confirmed the existence of the DEM imbalance in the system with increased Gilbert damping at one of the YIG interfaces. The reported results are indispensable to the quantitative estimation of the electromotive force in the spin-charge conversion experiments using ESR cavities. [ABSTRACT FROM AUTHOR]

Tapered coplanar waveguides with integrated photoconductors were designed, fabricated, and measured, with pulsed transmission results comparing well with High Frequency Structure Simulator simulations which predict increased confinement and electric field concentration in the tapered region. Devices made with titanium/gold metallisation were used to demonstrate transmission and confinement, while the magnetoresistive properties of devices with cobalt/copper multilayers were used to demonstrate the field concentration. In the latter case, a mathematical framework was developed to understand the relationship between tapering effects and the picosecond magnetoresistance response. [ABSTRACT FROM AUTHOR]

The finger geometry of embedded elastomeric comb capacitors significantly affects the electromechanical response of interdigitated capacitor (IDC) based soft sensors. When strain is applied to these IDC based soft sensors, the embedded soft combs are deformed, changing the sensor's capacitance to detect a variety of different mechanical loads. To better understand the effect of design parameters on sensor sensitivity, a comprehensive closed-form analytical model using geometric stretch and a parallel plate capacitance model in combination with a coplanar waveguide model to predict the strain response as a function of finger geometry and load orientation were developed. To validate this model, we compare the predicted response with computational and experimental methods using sensors with a combination of two different finger thicknesses and widths in a 4mm² area. Strong agreement was shown in all three results from the analytical model, the finite element analysis simulations, and the experiments validating that the sensitivity of IDC soft strain sensors can be tuned by finger geometry. [ABSTRACT FROM AUTHOR]

Voltage-tunable, interdigital capacitors (IDCs) were fabricated on Ba0.29Sr0.71TiO3 grown by hybrid molecular beam epitaxy (MBE). In this growth technique, we utilize the metal-organic precursor titanium tetraisopropoxide rather than solid-source Ti as with conventional MBE. Two samples of varying BaxSr(1-x)TiO3 (BST) thicknesses were fabricated and analyzed. High-quality, epitaxial Pt electrodes were deposited by sputtering from a high-purity Pt target at 825 °C. The Pt electrodes were patterned and etched by argon ion milling, passivated with reactively sputtered SiO2, and then metallized with lift-off Ti/Au. The fabricated devices consisted of two-port IDCs embedded in ground-signal-ground, coplanar waveguide (CPW) transmission lines to enable radiofrequency (RF) probing. The sample included open and thru de-embedding structures to remove pad and CPW parasitic impedances. Two-port RF scattering (S) parameters were measured from 100MHz to 40 GHz while DC bias was stepped from 0V to 100 V. The IDCs exhibit a high zerobias radio-frequency (RF) quality factor (Q) approaching 200 at 1 GHz and better than 2.3:1 capacitance tuning for the 300-nm-thick sample. Differences in the Q(V) and C(V) response with varying thicknesses indicate that unknown higher order material phenomena are contributing to the loss and tuning characteristics of the material. [ABSTRACT FROM AUTHOR]

Precise detection of spin resonance is of paramount importance to achieve coherent spin control in quantum computing. We present a setup for spin resonance measurements, which uses a dc- SQUID flux detector coupled to an antenna from a coplanar waveguide. The SQUID and the waveguide are fabricated from a 20 nm Nb thin film, allowing high magnetic field operation with the field applied parallel to the chip. We observe a resonance signal between the first and third excited states of Gd spins S=7/2 in a CaWO4 crystal, relevant for state control in multi-level systems. [ABSTRACT FROM AUTHOR]

Co-planar nanogap organic diodes were fabricated with smectic liquid crystalline materials of the benzothienobenzothiophene (BTBT) derivative by a spin-coating technique. A high rectification ratio of the order of 106 at ±3V was achieved when a liquid crystalline material of 2,7-didecyl benzo-thieno[ 3,2-b][1]benzothiophene (10-BTBT-10) was used in a device configuration of Al/10-BTBT- 10/pentafluorobenzenethiol-treated Au on a glass substrate, which was 4 orders higher than that of the device based on non-liquid crystalline materials of 2,7-dibutyl benzothieno[3,2-b][1]benzothiophene (4-BTBT-4) and BTBT. Similar results were also observed when another liquid crystalline material of ω, ω...-dioctylterthiophene (8-TTP-8) and a non-liquid crystalline material of terthiophene (TTP) were used. These improved rectifications can be ascribed to the self-assembly properties and controllable molecular orientation of liquid crystalline materials, which made uniform perpendicular oriented polycrystalline films favorable for superior charge transport in nano-channels. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (~7.6GHz) can be continuously tuned by as much as 95MHz in 270 ns without a change in the quality factor of 3000 at 2K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance. Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories. [ABSTRACT FROM AUTHOR]

Using conventional coplanar waveguides (CPWs), we excited spin waves with a wavelength λ down to 310 nm in a 200 nm thin yttrium iron garnet film grown by liquid phase epitaxy. Spinwave transmission was detected between CPWs that we separated by up to 2mm. For magnetostatic surface spin waves, we found a large nonreciprocity of 0.9 and a high group velocity vg of up to 5.4 km/s. The extracted decay length ld amounted to 0.86 mm. Small λ, high vg, and large ld are key figures of merit when aiming at non-charged based signal transmission and logic devices with spin waves. [ABSTRACT FROM AUTHOR]

Using a multi-layered printed circuit board, we propose a 3D architecture suitable for packaging superconducting chips, especially chips that contain two-dimensional qubit arrays. In our proposed architecture, the center strips of the buried coplanar waveguides protrude from the surface of a dielectric layer as contacts. Since the contacts extend beyond the surface of the dielectric layer, chips can simply be flip-chip packaged with on-chip receptacles clinging to the contacts. Using this scheme, we packaged a multi-qubit chip and performed single-qubit and two-qubit quantum gate operations. The results indicate that this 3D architecture provides a promising scheme for scalable quantum computing. [ABSTRACT FROM AUTHOR]

We generate a circularly polarized (CP) magnetic field using two crossed coplanar waveguides (TCCWs). By using the CP field, we selectively excite a ferromagnetic resonance between positively and negatively magnetized Co/Ni multilayers. The CP field arises from a superposition of Ampere fields generated by microwaves orthogonally propagating along the crossed arms of the TCCWs. The polarity of the magnetic field can be tuned continuously from circular to linear by exploiting a phase delay between the orthogonal microwaves. From a local measurement of the magneto-optical Kerr effect, we also find that the ellipticity of the CP field is distributed over the intersection of the TCCWs. These results indicate that TCCWs have great potential as CP-field generators that can be integrated into micron-scale electrical devices. [ABSTRACT FROM AUTHOR]

The fabrication, measurement, and modeling of radio-frequency (RF), tunable interdigital capacitors (IDCs) are described. High quality factors of 200 in the S/L-bands combined with a 47% tunability are achieved by utilizing epitaxial (Ba,Sr)TiO3 films grown by hybrid molecular beam epitaxy on LaAlO3 substrates. The fabricated devices consisted of one-port and two-port IDCs embedded in ground-signal-ground, coplanar waveguide transmission lines to enable RF probing. Wideband RF scattering parameters under bias were measured from 100 MHz to 40 GHz. A commutation quality factor averaging 6000 across the L band is achieved. These are the highest reported values in this band. [ABSTRACT FROM AUTHOR]

Separating the influence of hyperfine from spin-orbit interactions in spin-dependent carrier recombination and dissociation processes necessitates magnetic resonance spectroscopy over a wide range of frequencies. We have designed compact and versatile coplanar waveguide resonators for continuous-wave electrically detected magnetic resonance and tested these on organic lightemitting diodes. By exploiting both the fundamental and higher-harmonic modes of the resonators, we cover almost five octaves in resonance frequency within a single setup. The measurements with a common π-conjugated polymer as the active material reveal small but non-negligible effects of spin-orbit interactions, which give rise to a broadening of the magnetic resonance spectrum with increasing frequency. [ABSTRACT FROM AUTHOR]

We describe the design and characterization of superconducting coplanar waveguide cavities tailored to facilitate strong coupling between superconducting quantum circuits and single trapped Rydberg atoms. For initial superconductor-atom experiments at 4.2 K, we show that resonator quality factors above 104 can be readily achieved. Furthermore, we demonstrate that the incorporation of thick-film copper electrodes at a voltage antinode of the resonator provides a route to enhance the zero-point electric fields of the resonator in a trapping region that is 40 lm above the chip surface, thereby minimizing chip heating from scattered trap light. The combination of high resonator quality factor and strong electric dipole coupling between the resonator and the atom should make it possible to achieve the strong coupling limit of cavity quantum electrodynamics with this system. [ABSTRACT FROM AUTHOR]