As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor thirty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware.

A spectrum-inversion approach to extract information from MQ-MAS NMR spectra in glasses is presented. This allows the reconstruction of the underlying two-dimensional distribution of the isotropic chemical shift correlated to the quadrupolar interaction. The dependency upon the quadrupolar interaction and the RF field strength of coherence transfers involved in the MQ-MAS experiment are taken into account in the present approach. The performance of the inversion procedure is examined. Thereafter, we attempt to correlate the distributions of each interaction to structural local information. Two complex glasses (a borosilicate and a basaltic-like glass) have been studied using 17Al and 23Na 3Q-MAS NMR. These two nuclei allowed us to investigate their local environment. The interpretation of the different site distributions is discussed in terms of topological disorder, i.e., the distribution of specific geometrical parameters such as bond distances and angles. Using the semiempirical relationships previously established with crystalline silicate compounds, the distributions of the Na−O distance and the Al−O−Si bond angle have been determined from the extracted distributions of the isotropic chemical shift. The limits of the interpretation of quadrupolar interaction distributions are also discussed.

Out of equilibrium quasiparticles (QPs) are one of the main sources of decoherence in superconducting quantum circuits, and are particularly detrimental in devices with high kinetic inductance, such as high impedance resonators, qubits, and detectors. Despite significant progress in the understanding of QP dynamics, pinpointing their origin and decreasing their density remain outstanding tasks. The cyclic process of recombination and generation of QPs implies the exchange of phonons between the superconducting thin film and the underlying substrate. Reducing the number of substrate phonons with frequencies exceeding the spectral gap of the superconductor should result in a reduction of QPs. Indeed, we demonstrate that surrounding high impedance resonators made of granular aluminum (grAl) with lower gapped thin film aluminum islands increases the internal quality factors of the resonators in the single photon regime, suppresses the noise, and reduces the rate of observed QP bursts. The aluminum islands are positioned far enough from the resonators to be electromagnetically decoupled, thus not changing the resonator frequency, nor the loading. We therefore attribute the improvements observed in grAl resonators to phonon trapping at frequencies close to the spectral gap of aluminum, well below the grAl gap.Superconducting circuits play a central role in a variety of research and application areas, such as solid state quantum optics 1 , metrology 2,3 , and low temperature detectors 4,5 . In particular, the field of superconducting qubits has grown impressively during the last decade 6,7 . In these devices quantum states can live for up to tens of microseconds, while gate times can be as short as tens of nanoseconds [8][9][10][11] . Nevertheless, coherence times need to be further improved by orders of magnitude in order to be able to perform quantum error correction 12,13 with an affordable hardware overhead.One of the main sources of decoherence in superconducting devices at millikelvin temperatures are out of equilibrium quasiparticles (QPs) [14][15][16][17][18][19][20][21][22] , which can be viewed as broken Cooper pairs (CPs). Quasiparticles can be particularly damaging in high kinetic inductance circuits [23][24][25][26][27] , which are a promising avenue for protected qubits 28 and hybrid superconductingsemiconducting devices [29][30][31] . Proposed mechanisms for CP breaking include stray infrared radiation 32,33 , direct microwave drive 34,35 , and high energy phonons in the device substrate created by environmental or cosmic radioactivity [36][37][38] . The latter is particularly damaging because it gives rise to correlated QP bursts in multiple devices on the same chip 36,39 , possibly resulting in a) Both authors contributed equally b) Electronic

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27 Al MAS and multiquantum (MQ) MASNMR (magicangle spinning nuclear magnetic resonance) spectroscopy were used to study the substitution of silicon by aluminum in calcium silicate hydrates (C-S-H), which are the main component of hydrated portland cement. Synthetic C-S-H samples were prepared, and their chemical stability was studied. Two-dimensional 3Q-MASNMR spectra revealed the chemical shift and quadrupolar parameters (␦ iso , Q ) that labeled aluminum sites in the C-S-H. Tetrahedral aluminum was observed in the bridging and nonbridging sites of the silicate chains.

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Background Intensive care unit (ICU) patients with the most severe forms of acute coronary syndrome (ACS) require invasive therapies such as extracorporeal life support. The risk of bleeding in ICU patients with ACS treated with a dual antiplatelet therapy of aspirin and ticagrelor is unknown. The primary objective of this study was to compare the bleeding risk of ticagrelor and clopidogrel in ICU patients with ACS. Methods and findings We conducted a retrospective study based on a propensity score and a proportional hazards model. All patients with ACS hospitalized in the ICU of a French university hospital between January 2013 and January 2017 were included in the study. Bleeding during ICU stay was defined as all Thrombolysis in myocardial infarction (TIMI) major or minor events. A total of 155 patients were included in the study. According to propensity score matching, 57 patients treated with aspirin and ticagrelor were matched with 57 patients treated with aspirin and clopidogrel. Median (first-third quartile) Simplified Acute Physiology Score II was 61.5 (41.0-85.0). Bleeding during ICU stay occurred in 12 patients (21.1%) treated with clopidogrel and in 35 patients (61.4%) treated with ticagrelor (p<0.0001). This significant association was found for both TIMI major bleeding (12.3% vs. 35.1%, p = 0.004) and TIMI minor bleeding (8.8% vs. 26.3%, p = 0.01). The relative risk of bleeding occurrence during ICU stay was 2.60 (confidence interval 95%: 1.55-4.35) for ticagrelor compared to clopidogrel. No significant difference in ICU mortality was found between the two groups (45.6% in the clopidogrel group vs. 29.8% in the ticagrelor group, p = 0.08).