Dispersion Shift Research Articles

Exploring the interplay of dispersion, self-steepening, and self-frequency shift in nonlinear wave propagation

Exploring the interplay of dispersion, self-steepening, and self-frequency shift in nonlinear wave propagation

Pure kinetic inductance coupling for cQED with flux qubits

We demonstrate a qubit-readout architecture where the dispersive coupling is entirely mediated by a kinetic inductance. This allows us to engineer the dispersive shift of the readout resonator independent of the qubit and resonator capacitances. We validate the pure kinetic coupling concept and demonstrate various generalized flux qubit regimes from plasmon to fluxon, with dispersive shifts ranging from 60 kHz to 2 MHz at the half-flux quantum sweet spot. We achieve readout performances comparable to conventional architectures with quantum state preparation fidelities of 99.7% and 92.7% for the ground and excited states, respectively, and below 0.1% leakage to non-computational states.

Flux-pulse-assisted readout of a fluxonium qubit

Much attention has focused on the transmon architecture for large-scale superconducting quantum devices; however, the fluxonium qubit has emerged as a possible successor. With a shunting inductor in parallel to a Josephson junction, the fluxonium offers larger anharmonicity and stronger protection against dielectric loss, leading to higher coherence times as compared to conventional transmon qubits. The interplay between the inductive and Josephson energy potentials of the fluxonium qubit leads to a rich dispersive-shift landscape when tuning the external flux. Here, we propose to exploit the features in the dispersive shift to improve qubit readout. Specifically, we report on theoretical simulations showing improved readout times and error rates by performing the readout at a flux-bias point with large dispersive shift. We expand the scheme to include different error channels and show that with an integration time of 155 ns, flux-pulse-assisted readout offers about a 5-times improvement in the signal-to-noise ratio. Moreover, we show that the performance improvement persists in the presence of finite measurement efficiency combined with quasistatic flux noise and also when considering the increased Purcell rate at the flux-pulse-assisted readout point. We suggest a set of reasonable energy parameters for the fluxonium architecture that will allow for the implementation of our proposed flux-pulse-assisted readout scheme. Published by the American Physical Society 2024

Numerical experiment of phase-matched ion-based high-order harmonic generation in the water-window x-ray spectral region via electromagnetic envelope equation.

We present a phase-matching scheme for efficient high-order harmonic generation in the water-window x-ray spectral region using a 405-nm driving pulse. A high-intensity pulse (∼1016 W/cm2) is used to produce He1+ ions as the target medium, increasing the cutoff photon energy to the water-window x-ray spectral region. By adjusting the driving pulse divergence, the positive dipole phase variation balances the negative plasma dispersion and geometrical phase shift, achieving phase matching. Using the electromagnetic envelope equation coupled with the Keldysh ionization model, numerical experiments identify the optimal conditions. Results show that the relative conversion efficiencies of the 95th harmonic (4.26 nm) and the 169th harmonic (2.4 nm) reach 66% and 79% of the perfect phase-matching conditions, respectively.

Controlled refraction and focusing of spin waves determined by the Aharonov-Casher effect

The influence of an external static electric field on spin wave (SW) dynamics leads to an additional topological phase called the Aharonov-Casher (AC) phase. It is manifested as a shift in dispersion and the group velocity direction of the spin wave under the electric field. Within a linear approximation, the AC effect can be considered by including the Dzyaloshinskii-Moriya-like interaction between neighboring spins, which is proportional to the applied electric field. In this paper, we use these findings to examine the possibility of the electric field control of the refraction of coherently propagating SWs. This is done by studying the propagation SWs across the boundary between two regions of a homogeneous ferromagnetic film under the influence of different external electric fields. We have derived an analytical expression for a magnetic Snell's law and performed micromagnetic simulations to demonstrate how the AC phase shift can control SW refraction. This effect enables us to quantify the topological AC phase action. It presents a promising approach for guiding and manipulating the phase and energy flow of SWs using an external electric field, opening a way to control magnonic devices. Published by the American Physical Society 2024

Measurement of Small Photon Numbers in Circuit QED Resonators.

Off-resonant interaction of fluctuating photons in a resonator with a qubit increases the qubit dephasing rate. We use this effect to measure a small average number of intracavity photons that are coherently or thermally driven. For spectral resolution, we do this by subjecting the qubit to a Carr-Purcell-Meiboom-Gill sequence and record the qubit dephasing rate for various periods between qubit π pulses. The recorded data is then analyzed with formulas for the photon-induced dephasing rate derived for the non-Gaussian noise regime with an arbitrary ratio of the resonator dispersive shift to decay rate. We show that the presented Carr-Purcell-Meiboom-Gill dephasing rate formulas agree well with experimental results and demonstrate measurement of thermal and coherent photon populations at the level of a few 10^{-4}.

Parameter free AEWMA control chart for dispersion in semiconductor manufacturing

The study presents a new parameter free adaptive exponentially weighted moving average (AEWMA) control chart tailored for monitoring process dispersion, utilizing an adaptive approach for determining the smoothing constant. This chart is crafted to adeptly detect shifts within anticipated ranges in process dispersion by dynamically computing the smoothing constant. To assess its effectiveness, the chart’s performance is measured through concise run-length profiles generated from Monte Carlo simulations. A notable aspect is the incorporation of an unbiased estimator in computing the smoothing constant through the suggested function, thereby improving the chart’s capability to identify different levels of increasing and decreasing shifts in process dispersion. The comparison with an established adaptive EWMA-S2 dispersion chart highlights the considerable efficiency of the proposed chart in addressing diverse magnitudes of process dispersion shifts. Additionally, the study includes an application to a real-life dataset, showcasing the practicality and user-friendly nature of the proposed chart in real-world situations.

Characterization of a Transmon Qubit in a 3D Cavity for Quantum Machine Learning and Photon Counting

In this paper, we report the use of a superconducting transmon qubit in a 3D cavity for quantum machine learning and photon counting applications. We first describe the realization and characterization of a transmon qubit coupled to a 3D resonator, providing a detailed description of the simulation framework and of the experimental measurement of important parameters, such as the dispersive shift and the qubit anharmonicity. We then report on a Quantum Machine Learning application implemented on a single-qubit device to fit the u-quark parton distribution function of the proton. In the final section of the manuscript, we present a new microwave photon detection scheme based on two qubits coupled to the same 3D resonator. This could in principle decrease the dark count rate, favoring applications like axion dark matter searches.

Dispersion, ionic bonding and vibrational shifts in phospho-aluminosilicate glasses.

Understanding the relationships between structure and properties of aluminosilicate glasses is of interest in magmatic studies as well as for glass applications as mechanical or optical components. Glass properties may be tailored by the incorporation of additional elements, and here we studied the effect of phosphate incorporation on refractive index and the degree of ionic bonding in aluminosilicate glasses. The studied glasses in the system SiO2-Al2O3-Na2O-P2O5 had a metaluminous composition (Al:Na = 1) with the content of SiO2 ranging from 50 to 70 mol% and of P2O5 from 0 to 7.5 mol%. Refractive index was measured at four wavelengths from visible to near-infrared and found to decrease both with increasing P2O5 content (at the expense of NaAlO2) and with increasing SiO2 content (by substitution of SiO4 for AlO4 groups). This trend correlated with a decrease in density while, additionally, the formation of Al-O-P bonds with an SiO2-like structure may account for this change. The degree of ionic bonding, assessed via optical basicity and oxygen polarisability, decreased with increasing P2O5 and SiO2 content. Despite the complexity of the studied glasses, oxygen polarisability and optical basicity were found to follow Duffy's empirical equation for simple oxide glasses. In the high frequency infrared and Raman spectra, band shifts were observed with increasing P2O5 and SiO2 content. They indicated changing average bond strength of the glass network and showed a linear correlation with optical basicity.

Process dispersion monitoring: Innovative AEWMA control chart in semiconductor manufacturing

This study introduces a novel adaptive exponentially weighted moving average (AEWMA) control chart for monitoring process dispersion, employing adaptation to determine the smoothing constant. It is designed to effectively track shifts within expected ranges in process dispersion by computing the smoothing constant through a suggested adaptive approach. To determine its efficacy, the chart’s performance is evaluated by using smaller run-length profiles derived from Monte Carlo simulations. A key feature is the utilization of an unbiased estimator to calculate the smoothing constant via the proposed function, enhancing the chart’s ability to detect various magnitudes of decreasing and increasing process dispersion shifts. A comparison with an existing adaptive EWMA dispersion chart underscores the significant efficiency of the proposed chart across various types of process dispersion shift magnitudes. Moreover, the study encompasses a real-life dataset application, demonstrating the practical implementation and ease of use in real-world scenarios.

Simulation modeling with memory-type control charts for monitoring the process variability

Memory-type control charts, renowned for their effectiveness in identifying small deviations in the process variance, are commonly used to monitor the process variability. In this article, we introduce a new tool, the Quadruple Exponentially Weighted Moving Average (QEWMA) chart, which is designed for the specific purpose of monitoring changes in the process variability. We refer to this chart as the -QEWMA chart. The performance of the -QEWMA chart is assessed through an extensive series of Monte-Carlo simulations, carefully considering the run-length distribution. Comparing it with other well-known memory-type charts, it becomes evident that the -QEWMA chart excels in its ability to effectively detect small shifts in the process dispersion. To illustrate the practical application of this chart, we provide an example.

A novel Bayesian Max-EWMA control chart for jointly monitoring the process mean and variance: an application to hard bake process

In this article, we introduce a novel Bayesian Max-EWMA control chart under various loss functions to concurrently monitor the mean and variance of a normally distributed process. The Bayesian Max-EWMA control chart exhibit strong overall performance in detecting shifts in both mean and dispersion across various magnitudes. To evaluate the performance of the proposed control chart, we employ Monte Carlo simulation methods to compute their run length characteristics. We conduct an extensive comparative analysis, contrasting the run length performance of our proposed charts with that of existing ones. Our findings highlight the heightened sensitivity of Bayesian Max-EWMA control chart to shifts of diverse magnitudes. Finally, to illustrate the efficacy of our Bayesian Max-EWMA control chart using various loss functions, we present a practical case study involving the hard-bake process in semiconductor manufacturing. Our results underscore the superior performance of the Bayesian Max-EWMA control chart in detecting out-of-control signals.

Enhanced gain Raman amplifiers using different pumping schemes

Raman amplifiers (RAs) can be represented as one of the best solutions for transmission techniques, where they can compensate attenuation and transmit the optical signal to long-haul distances. This work proposes and investigates two cascaded models (multi-stages of RAs) for enhancing the received power and the overall gain. This study includes three fiber types: Dispersion Shifted Fiber, Truewave and Freelight fibers at 100 km distance and pumping powers of 500, 600 and 700 mW. The obtained results reveal that the best results gain is 46.46 dB and the power of output signal is 42.47 dBm achieved at 700 mW pump power with Truewave fiber. The models are compared with previously published work, where the gain and the output signal power are enhanced to more than 66.58–85.84%.

Modelling SiC MOSFET module threshold voltage (VTH) and impact of parallel device ΔVTH on short circuit robustness

In SiC modules, where several power MOSFETs are connected in parallel for high current conduction capability, the issue of threshold voltage (VTH) variation between individual devices can become problematic. In instances where the standard deviation of device VTH is minimized by appropriate VTH pre-screening, non-uniform VTH shift under bias-temperature-instability can lead to increased VTH dispersion and potentially poor current sharing. Although non-destructive for normal operation, VTH dispersion in surge events like short circuits can cause premature module failure. In this paper, experimental investigations backed by theoretical models have been developed to explain the relationship between device VTH dispersion and module VTH shift. This is done for Si and SiC MOSFETs. Five Si/SiC MOSFETs are paralleled in a custom printed-circuit-board allowing individual VTH and module VTH measurements. It is shown that the module VTH is typically between the smallest VTH and the mean VTH, depending on the VTH standard deviation. Using empirical models for MOSFETs in weak inversion derived from the measured subthreshold gate transfer characteristics, the model can estimate module VTH from a dispersion of individual MOSFET VTH. It can also predict the impact of non-uniform VTH shift between constituent devices on the overall module VTH. Finally, the impact of VTH mismatch on current sharing during short circuits in parallel connected SiC MOSFETs is presented. The results show that VTH mismatch in parallel connected SiC MOSFETs reduces the short circuit withstand time from 5 μs to 4.5 μs compared to VTH matched SiC MOSFETs.

Triple exponentially weighted moving average control chart with measurement error

Measurement error (M.E) can have a substantial impact on quality control applications, diminishing the sensitivity to detect changes in the mean or variance of quality characteristics. To monitor shifts in process mean and dispersion, Exponentially Weighted Moving Average (EWMA) and Cumulative Sum (CUSUM) control charts are commonly employed. In our research, we investigated the influence of M.E on the Triple Exponentially Weighted Moving Average (TEWMA) control chart. We assessed the performance of the control chart using Average Run Length (ARL) as the evaluation metric. To compute the ARL properties, we adopted the Monte-Carlo simulation method. A comparison section has been made to check the performance efficiency of the control chart with the existing EWMA control chart. The implementation of a control chart on a real data set is also presented.

Terahertz broadband near-perfect absorber with a single-layer coating on doped semiconductor

We demonstrate that a single-layer coating on a doped GaAs or Si substrate enables broadband antireflection and, hence, broadband perfect absorption in the terahertz frequency range. This broadband behavior can be generally expected when the substrate material has a Drude-type dispersion. Our mathematical analyses show that the reflection from Drude-type material may have an anomalously dispersive phase shift. The anomalous dispersion of the reflection phase is used to compensate for the normal dispersion of the accumulation phase in the single-layer coating film. Consequently, the antireflection conditions are satisfied in a wide frequency range, and broadband antireflection is achieved. Thus, broadband perfect absorption is realized with only a single-layer coating film on the substrate. Our method provides a simple and efficient approach to achieving broadband perfect absorption, which is critical in many applications such as radar stealth techniques and solar cells.

Strong parametric dispersive shifts in a statically decoupled two-qubit cavity QED system

Strong parametric dispersive shifts in a statically decoupled two-qubit cavity QED system

Higher-order rogue-wave fission in the presence of self-steepening and Raman self-frequency shift

Using the generalized nonlinear Schr\"odinger equation, we investigate how the effect of self-steepening and Raman-induced self-frequency shift impact higher-order rogue-wave solutions. We observe that each effect breaks apart the higher-order rogue wave, reducing it to its constituent fundamental parts, in a similar manner to how a higher-order soliton undergoes fission. Applying a local inverse-scattering technique, we show that under the effect of self-frequency shift, the emergence of a rogue wave significantly influences the surrounding wave background, triggering solitons, breathers, and new rogue waves. We demonstrate that under the combined effect of third-order dispersion, self-steepening, and Raman-induced self-frequency shift, the disintegrated elements of higher-order rogue waves become fundamental solitons, creating an asymmetrical spectral profile that generates both red- and blue-shifted frequency components. We also show the intermediary processes of the fission steps prior to soliton transformation which can only be observed in the presence of weak perturbations. These observations reveal the mechanisms that create a large number of solitons in the process of modulation instability-induced supercontinuum generation from a continuous-wave background in optical fibers.

Critical transitions and evolutionary hysteresis in movement: Habitat fragmentation can cause abrupt shifts in dispersal that are difficult to revert.

Under habitat fragmentation, plant species' survival hinges on the ability of individuals to disperse from one habitat patch to another. While there is evidence that severe habitat fragmentation leads to evolution of reduced dispersal ability and that such decreased mobility is generally detrimental for species' survival, it is unknown whether species adapt via a gradual loss in dispersal ability or via a sudden shift from frequent to infrequent dispersal between patches (i.e., a critical transition). Using both a spatially explicit deterministic and individual-based stochastic model of hydrochorous seed dispersal, we show that a small increase in inter-patch distance can generate an abrupt shift in plant seed dispersal strategy from long to short distances. Most importantly, we found that a substantial increase in connectivity between habitat fragments is required to reverse this loss of long-distance dispersal, due to an evolutionary hysteresis effect. Our theory prompts for re-consideration of the eco-evolutionary consequences of habitat fragmentation as restoring habitat connectivity may require restoration of much higher connectivity levels than currently assumed.

Energy Losses by the Interaction of Charged Particles with a Graphene Sheet

Using the fluid dynamics model, we studied the formation of graphene surface plasma when the charge is tilted to the graphene sheet for motion. We calculated the electron energy loss spectrum of electrons at different angles and proved that the resonance in the spectrum is related to the frequency of graphene surface plasma, as the electron velocity decreases, the dispersion shifts to higher energies. An increase in the tilt angle will also shift the dispersion energy in a higher range.