Quantum optics in the phase space - A tutorial on Gaussian states

In this tutorial, we introduce the basic concepts and mathematical tools needed for phase-space description of a very common class of states, whose phase properties are described by Gaussian Wigner functions: the Gaussian states. In particular, we address their manipulation, evolution and characterization in view of their application to quantum information.Comment: Tutorial. 23 pages, 1 figure. Updated version accepted for publication in EPJ - ST devoted to the memory of Federico Casagrand

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Kinetic resolution of a conformational transition and the ATP hydrolysis step using relaxation methods with a Dictyostelium myosin II mutant containing a single tryptophan residue

The fluorescence emission intensity from a conserved tryptophan residue (W501) located in the relay loop (F466 to L516) of the Dicytostelium discoideum myosin II motor domain is sensitive to ATP binding and hydrolysis. The initial binding process is accompanied by a small quench in fluorescence, and this is followed by a large enhancement that appears coincident with the hydrolysis step. Using temperature and pressure jump methods, we show that the enhancement process is kinetically distinct from but coupled to the hydrolysis step. The fluorescence enhancement corresponds to the open-closed transition (k(obs) approximately 1000 s(-1) at 20 degrees C). From the overall steady-state fluorescence signal and the presence or absence of a relaxation transient, we conclude that the ADP state is largely in the open state, while the ADP.AlF(4) state is largely closed. At 20 degrees C the open-closed equilibria for the AMP.PNP and ADP.BeF(x) complexes are close to unity and are readily perturbed by temperature and pressure. In the case of ATP, the equilibrium of this step slightly favors the open state, but coupling to the subsequent hydrolysis step gives rise to a predominantly closed state in the steady state. Pressure jump during steady-state ATP turnover reveals the distinct transients for the rapid open-closed transition and the slower hydrolysis step

The dynamics of a single tryptophan residue in the myosin catalytic domain

The dynamics of a single tryptophan residue in the myosin catalytic domai