Physical Review Applied

Journal: Physical Review Applied

Abbreviation

Phys. Rev. Applied

Publisher

American Physical Society

ISSN

2331-7019

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Publications1 - 10 of 133

Muon Interaction with Negative-U and High-Spin-State Defects: Differentiating between C and Si Vacancies in 4H-SiC
Woerle, Judith; Etzelmüller Bathen, Marianne; Prokscha, Thomas; et al. (2020)
Physical Review Applied
Low-energy muon-spin-rotation spectroscopy (LE-μ SR) is employed to study silicon and carbon vacancies in proton-irradiated 4H-Si C. We show that the implanted muon is quickly attracted to the negative Si vacancy (V Si), where it forms a paramagnetic muonium (Mu0) state, resulting in a reduction of the diamagnetic fraction. In samples with predominantly C vacancies (VC), on the other hand, the formation of Mu0 is very short lived and the muon quickly captures a second electron to form a diamagnetic Mu− state. The results are corroborated by density-functional calculations, where significant differences in the relaxation mechanism of the nearest-neighbor dangling bonds of the vacancies are discussed. We propose that the LE-μ SR technique is capable of differentiating between high-spin and negative-U behavior in semiconducting materials. Finally, our findings emphasize the large potential of LE-μ SR to probe near-surface semiconductor defects, a capability that is crucial for further development of many electronic and quantum technology applications.
Large Deformations of a Soft Porous Material
MacMinn, Christopher W.; Dufresne, Eric; Wettlaufer, John S. (2016)
Physical Review Applied
Rapid high-fidelity multiplexed readout of superconducting Qubits
Heinsoo, Johannes; Andersen, Christian Kraglund; Remm, Ants; et al. (2018)
Physical Review Applied
Multiscale Modeling of Metal-Oxide-Metal Conductive Bridging Random-Access Memory Cells: From Ab Initio to Finite-Element Calculations
Aeschlimann, Jan; Ducry, Fabian; Weilenmann, Christoph; et al. (2023)
Physical Review Applied
We present a multiscale simulation framework to compute the current versus voltage (I-V) characteristics of metal-oxide-metal structures building the core of conductive bridging random-access memory (CBRAM) cells and to shed light on their resistance switching properties. The approach relies on a finite-element model whose input material parameters are extracted either from ab initio or from machine-learned empirical calculations. The applied techniques range from molecular dynamics and nudged elastic band to electronic and thermal quantum transport. Such an approach drastically reduces the number of fitting parameters needed and makes the resulting modeling environment more accurate than traditional ones. The developed computational framework is then applied to the investigation of an Ag/a-SiO2/Pt CBRAM, reproducing experimental data very well. Moreover, the relevance of Joule heating is assessed by considering various cell geometries. It is found that self-heating manifests itself in devices with thin conductive filaments with few-nanometer diameters and at current concentrations in the tens-microampere range. With the proposed methodology it is now possible to explore the potential of not-yet fabricated memory cells and to reliably optimize their design.
Equivalent-circuit model that quantitatively describes domain-wall conductivity in ferroelectric LiNb O3
Zahn, Manuel; Beyreuther, Elke; Kiseleva, Iuliia; et al. (2024)
Physical Review Applied
Ferroelectric domain wall (DW) conductivity (DWC) can be attributed to two separate mechanisms: (a) the injection/ejection of charge carriers across the Schottky barrier formed at the (metal-)electrode-DW junction and (b) the transport of those charge carriers along the DW. Current-voltage (I-U) characteristics, recorded at variable temperatures from LiNbO3 (LNO) DWs, are clearly able to differentiate between these two contributions. Practically, they allow us to directly quantify the physical parameters relevant to the two mechanisms (a) and (b) mentioned above. These are, for example, the resistance of the DW, the saturation current, the ideality factor, and the Schottky barrier height of the electrode-DW junction. Furthermore, the activation energies needed to initiate the thermally activated electronic transport along the DWs can be extracted. In addition, we show that electronic transport along LNO DWs can be elegantly viewed and interpreted in an adapted semiconductor picture based on a double-diode, double-resistor equivalent-circuit model, the R2D2 model. Finally, our R2D2 model was checked for its universality by successfully fitting the I-U curves of not only z-cut LNO bulk DWs, but equally of z-cut thin-film LNO DWs, and of x-cut thin-film DWs as reported in literature.
Quantitative Diffractometric Biosensing
Blickenstorfer, Yves; Müller, Markus; Dreyfus, Roland; et al. (2021)
Physical Review Applied
Diffractometric biosensing is a promising technology to overcome critical limitations of refractometric biosensors, the dominant class of label-free optical transducers. These limitations manifest themselves by higher noise and drifts due to insufficient rejection of refractive index fluctuations caused by variation in temperature, solvent concentration, and, most prominently, nonspecific binding. Diffractometric biosensors overcome these limitations with inherent self-referencing on the submicron scale with no compromise on resolution. Despite this highly promising attribute, the field of diffractometric biosensors has only received limited recognition. A major reason is the lack of a general quantitative analysis. This hinders comparison to other techniques and amongst different diffractometric biosensors. For refractometric biosensors, on the other hand, such a comparison is possible by means of the refractive index unit (RIU). In this paper, we suggest the coherent surface mass density, Γcoh, as a quantity for label-free diffractometric biosensors with the same purpose as the RIU in refractometric sensors. It is easy to translate Γcoh to the total surface mass density Γtot , which is an important parameter for many assays. We provide a generalized framework to determine Γcoh for various diffractometric biosensing arrangements that enables quantitative comparison. Additionally, the formalism can be used to estimate background scattering in order to further optimize sensor configurations. Finally, a practical guide with important experimental considerations is given to enable readers of any background to apply the theory. Therefore, this paper provides a powerful tool for the development of diffractometric biosensors and will help the field to mature and unveil its full potential. © 2021 American Physical Society
High-Order Pulse-Echo Ultrasound
Hofmann, Urs A.T.; Pérez-López, Sergio; Estrada, Héctor; et al. (2022)
Physical Review Applied
Multiple reflections between transducer and imaged object can naturally occur in ultrasound imaging and other acoustic sensing applications such as sonar. The repeated interaction of the emitted wave front with the imaged object is traditionally regarded as an undesired reverberation artifact, often misinterpreted as fictitious acoustic boundaries. We introduce high-order reflection pulse-echo (HOPE) ultrasound, a method that leverages high-order reflections to improve on several aspects of conventional ultrasound imaging. HOPE is experimentally demonstrated to resolve submicrometer features by breaking through the sampling limit. The major contrast enhancement of the high reflection orders allowed defects within materials invisible to conventional scanning acoustic microscopy to be revealed. The technique is further shown to improve accuracy of frequency-dependent ultrasound attenuation measurements from biological tissues. HOPE ultrasound requires no additional hardware and is easy to implement, underscoring its potential to boost imaging performance in biomedical imaging, nondestructive testing, and other acoustic sensing applications.
Spin Detection via Parametric Frequency Conversion in a Membrane Resonator
Kosata, Jan; Zilberberg, Oded; Degen, Christian L.; et al. (2020)
Physical Review Applied
© 2020 American Physical Society. Recent demonstrations of ultracoherent nanomechanical resonators introduce the prospect of developing protocols for solid-state sensing applications. Here, we propose to use two coupled ultracoherent resonator modes on a Si3N4 membrane for the detection of small nuclear spin ensembles. To this end, we employ parametric frequency conversion between nondegenerate modes. The nondegenerate modes result from coupled degenerate resonators, and the parametric conversion is mediated by periodic inversions of the nuclear spins in the presence of a magnetic scanning tip. We analyze potential noise sources and derive the achievable signal-to-noise ratio with typical experimental parameter values. Our proposal reconciles the geometric constraints of optomechanical systems with the requirements of scanning force microscopy and brings forth a promising platform for spin-phonon interaction and spin imaging.
Characterizing Multipartite non-Gaussian Entanglement for a Three-Mode Spontaneous Parametric Down-Conversion Process
Tian, Mingsheng; Xiang, Yu; Sun, Feng-Xiao; et al. (2022)
Physical Review Applied
Very recently, strongly non-Gaussian states have been observed via a direct three-mode spontaneous parametric down-conversion in a superconducting cavity [Phys. Rev. X 10, 011011 (2020)]. The created multiphoton non-Gaussian correlations are attractive and useful for various quantum information tasks. However, how to detect and classify multipartite non-Gaussian entanglement has not yet been completely understood. Here, we present an experimentally practical method to characterize continuous-variable multipartite non-Gaussian entanglement, by introducing a class of nonlinear squeezing parameters involving accessible higher-order moments of phase-space quadratures. As these parameters can depend on arbitrary operators, we consider their analytical optimization over a set of practical measurements, in order to detect different classes of multipartite non-Gaussian entanglement ranging from fully separable to fully inseparable. We demonstrate that the nonlinear squeezing parameters act as an excellent approximation to the quantum Fisher information within accessible third-order moments. The level of the nonlinear squeezing quantifies the metrological advantage provided by those entangled states. Moreover, by analyzing the above-mentioned experiment, we show that our method can be readily used to confirm fully inseparable tripartite non-Gaussian entangled states by performing a limited number of measurements without requiring full knowledge of the quantum state.
Learning-agent-based approach to the characterization of open quantum systems
Fioroni, Lorenzo; Rojkov, Ivan; Reiter, Florentin (2025)
Physical Review Applied
Characterizing quantum processes is crucial for the execution of quantum algorithms on available quantum devices. A powerful framework for this purpose is the Quantum Model Learning Agent (QMLA), which characterizes a given system by learning its Hamiltonian via adaptive generations of informative experiments and their validation against simulated models. Identifying the incoherent noise of a quantum device in addition to its coherent interactions is, however, as essential. Precise knowledge of such imperfections of a quantum device allows one to devise strategies to mitigate detrimental effects, for example, via quantum error correction. We introduce the open Quantum Model Learning Agent (oQMLA) framework to account for Markovian noise through the Liouvillian formalism. By simultaneously learning the Hamiltonian and jump operators, oQMLA independently captures both the coherent and incoherent dynamics of a system. The added complexity of open systems necessitates advanced algorithmic strategies. Among these, we implement regularization to steer the algorithm toward plausible models and an unbiased metric to evaluate the quality of the results. We validate our implementation in simulated scenarios of increasing complexity, demonstrating its robustness to hardware-induced measurement errors and its ability to characterize systems using only local operations. Additionally, we develop a scheme to interface oQMLA with a publicly available superconducting quantum computer, showcasing its practical utility. These advancements represent a significant step toward improving the performance of quantum hardware and contribute to the broader goal of advancing quantum technologies and their applications.

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