Universal Approximation Theorem and error bounds for quantum neural networks and quantum reservoirs

Universal approximation theorems are the foundations of classical neural networks, providing theoretical guarantees that the latter are able to approximate maps of interest. Recent results have shown that this can also be achieved in a quantum setting, whereby classical functions can be approximated by parameterised quantum circuits. We provide here precise error bounds for specific classes of functions and extend these results to the interesting new setup of randomised quantum circuits, mimicking classical reservoir neural networks. Our results show in particular that a quantum neural network with $\mathcal{O}(\varepsilon^{-2})$ weights and $\mathcal{O} (\lceil \log_2(\varepsilon^{-1}) \rceil)$ qubits suffices to achieve accuracy $\varepsilon>0$ when approximating functions with integrable Fourier transform.Comment: 20 pages, 0 figur

Assessing change agency in urban experiments for sustainability transitions

Experimentation has become one of the prevailing modes of governing the transition toward sustainable practices in urban environments. The spatial variation of urban sustainability transition has been attributed to a variety of conditions erected at different spatial scales. What remains less well-understood is how spatial situatedness shapes agency in urban experiments and the shapes agency can take is a field that requires further research and frameworks. The paper addresses this gap by introducing a framework from the literature on regional development, identifying three distinct types of agency that shape regional development processes. Combining this framework with a process perspective on urban experiments, we develop an analytical framework, which allows for a more granular understanding of agency in urban sustainability transitions. The analytical framework is then brought to use in a case study of an urban experiment aiming to electrify public transport in Gothenburg, Sweden.publishedVersio

Pseudoscalar transition form factors and the hadronic light-by-light contribution to the muon g−2g-2

We report on our progress toward the computation of the $\pi^0$, $\eta$ and $\eta^{\prime}$ transition form factors using staggered quarks on $N_f=2+1+1$ gauge ensembles generated by the Budapest-Marseille-Wuppertal collaboration. These form factors are essential ingredients to evaluate the pseudoscalar-pole contributions to the hadronic light-by-light scattering in the muon $g-2$. Preliminary results for the pseudoscalar-pole contributions are presented, at finite lattice spacing, for all three light mesons.Comment: 10 pages, 7 figures, contribution to the 39th International Symposium on Lattice Field Theor

Hydrogen-resistant refractories for direct reduced iron production

In the steelmaking industry, the largest share of CO2 emissions comes from the reduction of iron ore. A switch from the blast furnace (BF) / basic oxygen furnace (BOF) route to the direct reduced iron (DRI) process with natural gas followed by the electric arc furnace (EAF) already enables CO2 savings of up to 38%. However, in order to meet the mid- to long-term CO2 targets of the iron and steel industry, further measures are required. Most DRI plants are currently operating on natural gas, which results in approximately 60% hydrogen in the process gas. However, currently projects are underway to determine if DRI units can operate at hydrogen levels at or close to 100%, which could further reduce CO2 emissions by more than 80%. In this context, it is important to consider the impact of hydrogen on the refractory lining in the DRI shaft kiln. Previous studies have shown that hydrogen can permeate through refractories and reduce ceramic oxides under certain process conditions. Silica-containing materials are reported to be especially susceptible to hydrogen attack. However, a deeper understanding of corrosion mechanisms is still needed. This article presents the first results of experimental work carried out by RHI Magnesita on the impact of hydrogen on refractory systems. Investigations were conducted on the effect of hydrogen exposure on the composition and microstructure of refractory bricks. This enables refractories to be identified that are suitable for lining a DRI shaft kiln where hydrogen is used as a reductant and will support the development of novel hydrogen-resistant refractory solutions

REM sleep stabilizes hypothalamic representation of feeding behavior

During rapid eye movement (REM) sleep, behavioral unresponsiveness contrasts strongly with intense brain-wide neural network dynamics. Yet, the physiological functions of this cellular activation remain unclear. Using in vivo calcium imaging in freely behaving mice, we found that inhibitory neurons in the lateral hypothalamus (LHvgat) show unique activity patterns during feeding that are reactivated during REM, but not non-REM, sleep. REM sleep-specific optogenetic silencing of LHvgat cells induced a reorganization of these activity patterns during subsequent feeding behaviors accompanied by decreased food intake. Our findings provide evidence for a role for REM sleep in the maintenance of cellular representations of feeding behavior

Advanced analysis of fan noise measurements supported by theoretical source models

With the objective to improve the understanding of the dominant fan noise source mechanisms a comprehensive experimental study was conducted at a low speed fan test rig. The aerodynamic fan map as well as the acoustic characteristics of the fan were measured for a new blade integrated disk (Blisk) rotor with systematic variation of the shaft speed and throttling. The interpretation of the results is supported by simulations of the experiment with a physics based analytical in-house tool for fan noise prediction. For the acoustic measurements an array of wall-flushed microphones was used in the inlet section. By means of radial mode analysis techniques, the broadband and tonal sound powers are calculated for each operating point. In the obtained comprehensive database systematic variations of the tonal and broadband sound power with the flow rate are found. These patterns can only partly be correlated to the varying incidence angle of the rotor blades. Comparing the mode distributions of the measured noise and the analytical models then allows conclusions on the predominant noise sources of rotor-stator interaction and inflow-rotor interaction

Experimental Investigation of Inflow-Distortion-Induced Tonal Noise in a Sub-Sonic Fan Test Rig

Experimental investigation on the influence of inflow distortions on fan noise was performed at the low-speed Co-/Counter Rotating Acoustic Fan Test rig (CRAFT). The investigated fan stage is designed such that the dominant interaction modes at the first and second BPF are excited weakly in upstream direction, but strongly in downstream direction, due to the mode propagation angle. Two major tonal source mechanisms are described in the literature and addressed in this work. The first mechanism is the inflow-distortion-rotor interaction, which can generate high sound power levels at the blade passing frequencies at high blade tip mach numbers or low rotor blade counts. For the measurements performed this source seems to be relevant only for extreme inflow distortion cases. The second mechanism is linked to the modulation of the rotor-stator interaction (RSI), which is caused by the periodically fluctuating incidence angle and the resulting fluctuation of the rotor wakes shape. The sources distorted phase and amplitude lead to a less effective constructive interference of the conventional interaction modes and a less a destructive interference of the adjacent modes. As consequence, a broader mode spectrum is propagating to the measurement sections. The overall sound power level for our specific fan stage can be more than 7 dB higher or 1 dB lower than the baseline, depending on the inflow distortion profile and BPF harmonic

Analytical modeling of silicon microring and microdisk modulators with electrical and optical dynamics

We propose an analytical time-domain model for microring and microdisk modulators, which considers both their electrical and optical properties. Theory of the dynamics of microring/microdisk is discussed, and general solutions to the transfer matrix representation are presented. Both static and dynamic predictions from the model are compared to measurement results to demonstrate the accuracy of our model. Static predictions and measurements are presented for power and phase responses, whereas dynamic predictions and measurements are presented for small-signal and large-signal operations. The model verifies that the chirping and modulation bandwidth of the modulators depend on the detuning state. Finally, the accuracy and scalability of several techniques employed in the model are discussed

Hadronic vacuum polarization: comparing lattice QCD and data-driven results in systematically improvable ways

The precision with which hadronic vacuum polarization (HVP) is obtained determines how accurately important observables, such as the muon anomalous magnetic moment, a_\mu, or the low-energy running of the electromagnetic coupling, \alpha, are predicted. The two most precise approaches for determining HVP are: dispersive relations combined with e+e- to hadrons cross-section data, and lattice QCD. However, the results obtained in these two approaches display significant tensions, whose origins are not understood. Here we present a framework that sheds light on this issue and, if the two approaches can be reconciled, allows them to be combined. Via this framework, we test the hypothesis that the tensions can be explained by modifying the R-ratio in different intervals of center-of-mass energy sqrt(s). As ingredients, we consider observables that have been precisely determined in both approaches. These are the leading hadronic contributions to a_\mu, to the so-called intermediate window observable and to the running of \alpha between spacelike virtualities 1GeV^2 and 10GeV^2 (for which only a preliminary lattice result exists). Our tests take into account all uncertainties and correlations, as well as uncertainties on uncertainties in the lattice results. Among our findings, the most striking is that results obtained in the two approaches can be made to agree for all three observables by modifying the \rho peak in the experimental spectrum. In particular, we find that this requires a common ~5\% increase in the contributions of the peak to each of the three observables. This finding is robust against the presence or absence of one of the constraining observables. However, such an increase is much larger than the uncertainties on the measured R-ratio. We also discuss a variety of generalizations of the methods used here, as well as the limits in the information that can be extracted...Comment: 38 pages, 8 figure