Quantum Phase Tomography of a Strongly Driven Qubit

The interference between repeated Landau-Zener transitions in a qubit swept through an avoided level crossing results in Stueckelberg oscillations in qubit magnetization. The resulting oscillatory patterns are a hallmark of the coherent strongly-driven regime in qubits, quantum dots and other two-level systems. The two-dimensional Fourier transforms of these patterns are found to exhibit a family of one-dimensional curves in Fourier space, in agreement with recent observations in a superconducting qubit. We interpret these images in terms of time evolution of the quantum phase of qubit state and show that they can be used to probe dephasing mechanisms in the qubit.Comment: 5 pgs, 4 fg

On Convergence of the Inexact Rayleigh Quotient Iteration with the Lanczos Method Used for Solving Linear Systems

For the Hermitian inexact Rayleigh quotient iteration (RQI), the author has established new local general convergence results, independent of iterative solvers for inner linear systems. The theory shows that the method locally converges quadratically under a new condition, called the uniform positiveness condition. In this paper we first consider the local convergence of the inexact RQI with the unpreconditioned Lanczos method for the linear systems. Some attractive properties are derived for the residuals, whose norms are $\xi_{k+1}$'s, of the linear systems obtained by the Lanczos method. Based on them and the new general convergence results, we make a refined analysis and establish new local convergence results. It is proved that the inexact RQI with Lanczos converges quadratically provided that $\xi_{k+1}\leq\xi$ with a constant $\xi\geq 1$. The method is guaranteed to converge linearly provided that $\xi_{k+1}$ is bounded by a small multiple of the reciprocal of the residual norm $\|r_k\|$ of the current approximate eigenpair. The results are fundamentally different from the existing convergence results that always require $\xi_{k+1}<1$, and they have a strong impact on effective implementations of the method. We extend the new theory to the inexact RQI with a tuned preconditioned Lanczos for the linear systems. Based on the new theory, we can design practical criteria to control $\xi_{k+1}$ to achieve quadratic convergence and implement the method more effectively than ever before. Numerical experiments confirm our theory.Comment: 20 pages, 8 figures. arXiv admin note: text overlap with arXiv:0906.223

Pulse calibration and non-adiabatic control of solid-state artificial atoms

Transitions in an artificial atom, driven non-adiabatically through an energy-level avoided crossing, can be controlled by carefully engineering the driving protocol. We have driven a superconducting persistent-current qubit with a large-amplitude, radio-frequency field. By applying a bi-harmonic waveform generated by a digital source, we demonstrate a mapping between the amplitude and phase of the harmonics produced at the source and those received by the device. This allows us to image the actual waveform at the device. This information is used to engineer a desired time dependence, as confirmed by detailed comparison with simulation.Comment: 4.1 pages, 3 figure

Prevalence of oral anticoagulant therapy in clinical practice in patients hospitalized with acute ischemic stroke

Aim. To evaluate the prevalence of oral anticoagulant therapy at the outpatient and inpatient stages in patients hospitalized with ischemic stroke.Material and methods. This open observational prospective real-world study included 114 patients with atrial fibrillation (AF) hospitalized with confirmed stroke.Results. Only 26,3% of patients with AF hospitalized with a confirmed diagnosis of ischemic stroke took anticoagulants (70% — direct oral anticoagulants (DOACs), 30% — warfarin). At the same time, among those taking warfarin, only one patient had normal international normalized ratio (INR) at the time of hospitalization (INR 2,6). In all other cases, the INR was &lt;2. Of the 105 patients discharged at the outpatient stage, 93 (88,6%) patients were prescribed anticoagulants, and in most cases — DOACs (89 (84,8%)). 4 (3,8%) patients insisted on continuing warfarin therapy. There were following reasons for not prescribing DOACs: 4 (33,3%) patients were diagnosed with acute peptic ulcer during hospitalization, 2 (16,7%) — hemorrhagic transformation of the ischemic focus.Conclusion. One of the common reasons for stroke in outpatients with AF is the refusal to take oral anticoagulants or insufficient INR control when taking warfarin

Electron neutrino tagging through tertiary lepton detection

We discuss an experimental technique aimed at tagging electron neutrinos in multi-GeV artificial sources on an event-by-event basis. It exploits in a novel manner calorimetric and tracking technologies developed in the framework of the LHC experiments and of rare kaon decay searches. The setup is suited for slow-extraction, moderate power beams and it is based on an instrumented decay tunnel equipped with tagging units that intercept secondary and tertiary leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers are able to reduce the \nue contamination originating from K_e3 decays by about one order of magnitude. Only a limited suppression (~60%) is achieved for \nue produced by the decay-in-flight of muons; for low beam powers, similar performance as for K_e3 can be reached supplementing the tagging system with an instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ

Advances in multispectral and hyperspectral imaging for archaeology and art conservation

Multispectral imaging has been applied to the field of art conservation and art history since the early 1990s. It is attractive as a noninvasive imaging technique because it is fast and hence capable of imaging large areas of an object giving both spatial and spectral information. This paper gives an overview of the different instrumental designs, image processing techniques and various applications of multispectral and hyperspectral imaging to art conservation, art history and archaeology. Recent advances in the development of remote and versatile multispectral and hyperspectral imaging as well as techniques in pigment identification will be presented. Future prospects including combination of spectral imaging with other noninvasive imaging and analytical techniques will be discussed

Incidence and prognostic value of acute kidney injury in pulmonary embolism: data from the SIRENA registry

Aim. To evaluate the incidence and severity of acute kidney injury (AKI), as well as its ability to reclassify the risk of premature mortality and association with inhospital mortality in patients with pulmonary embolism (PE) in the Russian population.Material and methods. From April 2018 to April 2019, the SIRENA Russian Multicenter Registry included patients with PE, as well as the deceased, in whom the PE was detected by autopsy. AKI was diagnosed according to current KDIGO guidelines (2012). Creatinine calculated according to the MDRD equation and corresponding to a glomerular filtration rate of 75 ml/min/1,73 m2 (baseline) was taken as the initial one, with subsequent assessment relative to the parameter value upon admission. The risk stratification of early death was carried out in accordance with the current ESC clinical guidelines (2019).Results. A total of 604 patients with PE were examined (men — 293 (49%), women — 311 (51%), mean age — 64±15 years). AKI was diagnosed in 223 (37%) of them. Stage 1 AKI was detected in 146 (65%), 2 — in 55 (25%), 3 — in 22 (10%) patients. Prior chronic kidney disease was recorded in 61 (10%) patients. Seventy-one (12%) patients had a high risk of death, 364 (61%) — intermediate risk, and 164 (27%) — low risk. The AKI incidence increased as the severity of PE increased: at low risk of death — 26%, intermediate — 38%, high — 59% (p&lt;0,0001). In total, 107 (18%) patients died in the hospital. AKI led to an increase in mortality within following risk groups: at low risk, this effect was a trend (6 (5%) vs 6 (14%); p=0,052); at intermediate and high risk, significant differences was obtained (30 (13%) vs 41 (30%), p&lt;0,001; 4 (14%) vs 19 (45%), p=0,006, respectively). Multivariate Cox regression demonstrated that AKI is a predictor of inhospital death (odds ratio (OR), 3,66 (95% confidence interval (CI): 2,37-5,66; p&lt;0,0001), regardless of increased troponin levels (OR, 1,31 (95% CI: 0,80-2,14; p=0,28) and right ventricular dysfunction (OR, 1,23 (95% CI: 0,74-2,04; p=0,42).Conclusion. Thirty-seven percent of Russian patients with PE have AKI diagnosed by baseline creatinine. In 2/3 of the examined patients, stage 1 AKI is observed. The AKI incidence increases as the severity of PE increases. The presence of AKI reclassifies patients into a higher risk category for death and is associated with a significant increase in inhospital mortality