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The Ramsey sequence is a canonical example of a quantum phase measurement for a spin qubit. In Ramsey measurements, the measurement efficiency can be optimized through careful selection of settings for the phase accumulation time setting, τ . This paper implements a sequential Bayesian experiment design protocol in low-fidelity Ramsey measurements, and its performance is compared to a previously reported adaptive heuristic protocol, a quantum phase estimation algorithm, and random setting choices. A workflow allowing measurements and design calculations to run concurrently largely eliminates computation time from measurement overhead. When precession frequency is the lone parameter to estimate, the Bayesian design is faster by factors of roughly 2 and 4 and 5 relative to the adaptive heuristic, random τ choices and the quantum phase estimation algorithm respectively. When four parameters are to be determined, Bayesian experiment design and random τ choices can converge to roughy equivalent sensitivity, but the Bayesian method converges 4 times faster.

Technologically relevant magnetic nanoparticles for biomedicine are rarely noninteracting single-domain nanoparticles; instead, they are often interacting, with complex physical and magnetic structures. In this paper, we present both experimental and simulated magnetic hysteresis loops of a system of magnetic nanoparticles with significant interparticle interactions and a well-defined intraparticle structure which are used for magnetic nanoparticle hyperthermia cancer treatment. Experimental measurements were made at 11 K on suspensions of magnetic nanoparticles dispersed in H 2 O which have been frozen in a range of applied magnetic fields to tune the interparticle interactions. Micromagnetic simulations of hysteresis loops investigated the roles of particle orientation with respect to the field and of particle chaining in the shape of the hysteresis loops. In addition, we present an analysis of the magnetic anisotropy arising from the combination of magnetocrystalline and shape anisotropy, given the well-defined internal structure of the nanoparticles. We find that the shape of the experimental hysteresis loops can be explained by the internal magnetic structure, modified by the effects of interparticle interactions from chaining.

Traditional metrology has been unable to adequately address the needs of the emerging integrated circuits (ICs) at the nano scale; thus, new metrology and techniques are needed. For example, the reliability challenges in fabrication need to be well understood and controlled to facilitate mass production of through-substrate-via (TSV) enabled three-dimensional integrated circuits (3D-ICs). This requires new approaches to the metrology. In this paper, we use the microwave propagation characteristics to study the reliability issues that precede the physical damage caused by electromigration in the Cu-filled TSVs. The pre-failure microwave insertion losses and group delay are dependent on both the device temperature and the amount of current forced through the devices-under-test. The microwave insertion losses increase with the increase in the test temperature, while the group delay increases with the increase in the forced direct current magnitude. The microwave insertion losses are attributed to the defect mobility at the Cu-TiN interface, and the group delay changes are due to resistive heating in the interconnects, which perturbs the dielectric properties of the cladding dielectrics of the copper fill in the TSVs. https://doi.org/10.1063/1.4992135.

This paper describes a metal-insulator-semiconductor (MIS) capacitor with flat capacitance voltage characteristics and a small quadratic voltage capacitance coefficient. The device characteristics resemble a metal-insulator-metal diode except that here the capacitance depends on illumination and exhibits a strong frequency dispersion. The device incorporates Fe nanoparticles (NPs), mixed with SrF 2 , which are embedded in an insulator stack of SiO 2 and HfO 2 . Positively charged Fe ions induce dipole type traps with an electronic polarization that is enhanced by photogenerated carriers injected from the substrate and/or by inter nanoparticle exchange of carriers. The obtained characteristics are compared with those of five other MIS structures: two based on Fe NPs, one with and the other without SrF 2 sublayers. Additionally, devices contain Co NPs embedded in SrF 2 sublayers, and finally, two structures have no NPs, with one based on a stack of SiO 2 and HfO 2 and the other which also includes SrF 2 . Only structures containing Fe NPs, which are incorporated into SrF 2 , yield a voltage independent capacitance, the level of which can be changed by illumination. These properties are essential in radio frequency/analog mixed signal applications.

In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobate-lead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows us to explain this unexpected result with the presence of complex interface structures between the different layers.

Pauli-spin blockade (PSB) is a transport phenomenon in double quantum dots that allows for a type of spin to charge conversion often used to probe fundamental physics such as spin relaxation and singlet-triplet coupling. In this paper, we theoretically explore Pauli-spin blockade as a function of magnetic field B applied parallel to the substrate. In the well-studied low magnetic field regime, where PSB occurs in the forward (1, 1) → (0, 2) tunneling direction, we highlight some aspects of PSB that are not discussed in detail in existing literature, including the change in size of both bias triangles measured in the forward and reverse biasing directions as a function of B . At higher fields, we predict a crossover to "reverse PSB" in which current is blockaded in the reverse direction due to the occupation of a spin singlet as opposed to the traditional triplet blockade that occurs at low fields. The onset of reverse PSB coincides with the development of a tail like feature in the measured bias triangles and occurs when the Zeeman energy of the polarized triplet equals the exchange energy in the (0, 2) charge configuration. In Si quantum dots, these fields are experimentally accessible; thus, this work suggests a way to observe a crossover in magnetic field to qualitatively different behavior.

Magnetic Particle Imaging (MPI) is an emerging imaging technique that uses magnetic nanoparticles as tracers. In order to analyze the quality of nanoparticles developed for MPI, a Magnetic Particle Spectrometer (MPS) is often employed. In this paper, we describe results for predictions of the nanoparticle harmonic spectra obtained in a MPS using three models: the first uses the Langevin function, which does not take into account finite magnetic relaxation; the second model uses the magnetization equation by Shliomis (Sh), which takes into account finite magnetic relaxation using a constant characteristic time scale; and the third model uses the magnetization equation derived by Martsenyuk, Raikher, and Shliomis (MRSh), which takes into account the effect of magnetic field magnitude on the magnetic relaxation time. We make comparisons between these models and with experiments in order to illustrate the effects of field-dependent relaxation in the MPS. The models results suggest that finite relaxation results in a significant drop in signal intensity (magnitude of individual harmonics) and in faster spectral decay. Interestingly, when field dependence of the magnetic relaxation time was taken into account, through the MRSh model, the simulations predict a significant improvement in the performance of the nanoparticles, as compared to the performance predicted by the Sh equation. The comparison between the predictions from models and experimental measurements showed excellent qualitative as well as quantitative agreement up to the 19th harmonic using the Sh and MRSh equations, highlighting the potential of ferrohydrodynamic modeling in MPI.

This paper presents a three-dimensional microwave metamaterial absorber based on the stand-up resistive film patch array. The absorber has wideband absorption, lightweight, and polarization-independent properties. Our design comes from the array of unidirectional stand-up resistive film patches backed by a metallic plane, which can excite multiple standing wave modes. By rolling the resistive film patches as a square enclosure, we obtain the polarization-independent property. Due to the multiple standing wave modes, the most incident energy is dissipated by the resistive film patches, and thus, the ultra-wideband absorption can be achieved by overlapping all the absorption modes at different frequencies. Both the simulated and experimental results show that the absorber possesses a fractional bandwidth of 148.2% with the absorption above 90% in the frequency range from 3.9 to 26.2 GHz. Moreover, the proposed absorber is extremely lightweight. The areal density of the fabricated sample is about 0.062 g/cm 2 , which is approximately equivalent to that of eight stacked standard A4 office papers. It is expected that our proposed absorber may find potential applications such as electromagnetic interference and stealth technologies.

We present in this paper a systematic study of the distance dependent detection characteristics of the newly developed micro-ring resonator (MRR)-based ultrasonic detector for photoacoustic microscopy (PAM). A simple analytic model was first developed to study the steady-state response to the continuous ultrasonic waves. While placing the MRR detector at the acoustic far-field provides longer working distance and broader field of view, the detection at acoustic near-field offers the improved sensitivity and broader bandwidth but at the cost of reduction in the field of view. Furthermore, a numerical model was developed to analyze the transient response to the photoacoustic-induced impulsive waves. Notably, far-field detection exhibits a flat wavefront of its response pattern in the time domain while large distortions are clearly visible in the case of near-field detection. Finally, both analytic and numerical models are validated by experimental studies. This work establishes a theoretical framework for quantitatively analyzing the trade-offs between near-field and far-field detection using MRR detector, creating a guideline for optimizing the PAM for various applications in biomedical imaging and diagnostics.