Symmetries of the squeeze-driven Kerr oscillator

We study the symmetries of the static effective Hamiltonian of a driven superconducting nonlinear oscillator, the so-called squeeze-driven Kerr Hamiltonian, and discover a remarkable quasi-spin symmetry $su(2)$ at integer values of the ratio $\eta=\Delta /K$ of the detuning parameter $\Delta$ to the Kerr coefficient $K$. We investigate the stability of this newly discovered symmetry to high-order perturbations arising from the static effective expansion of the driven Hamiltonian. Our finding may find applications in the generation and stabilization of states useful for quantum computing. Finally, we discuss other Hamiltonians with similar properties and within reach of current technologies.Comment: 19 pages, 14 figure

Driving superconducting qubits into chaos

Kerr parametric oscillators are potential building blocks for fault-tolerant quantum computers. They can stabilize Kerr-cat qubits, which offer advantages towards the encoding and manipulation of error-protected quantum information. Kerr-cat qubits have been recently realized with the SNAIL transmon superconducting circuit by combining nonlinearities and a squeezing drive. These superconducting qubits can lead to fast gate times due to their access to large anharmonicities. However, we show that when the nonlinearities are large and the drive strong, chaos sets in and melts the qubit away. We provide an equation for the border between regularity and chaos and determine the regime of validity of the Kerr-cat qubit, beyond which it disintegrates. This is done through the quantum analysis of the quasienergies and Floquet states of the driven system, and is complemented with classical tools that include Poincar\'e sections and Lyapunov exponents. By identifying the danger zone for parametric quantum computation, we uncover another application for driven superconducting circuits, that of devices to investigate quantum chaos.Comment: 12 pages, 5 figure

Quantum tunneling and level crossings in the squeeze-driven Kerr oscillator

The quasi-energy spectrum recently measured in experiments with a squeeze-driven superconducting Kerr oscillator showed good agreement with the energy spectrum of its corresponding static effective Hamiltonian. The experiments also demonstrated that the dynamics of low-energy states can be explained with the same emergent static effective model. The spectrum exhibits real (avoided) level crossings for specific values of the Hamiltonian parameters, which can then be chosen to suppress (enhance) quantum tunneling. Here, we analyze the spectrum and the dynamics of the effective model up to high energies, which should soon be within experimental reach. We show that the parameters values for the crossings, which can be obtained from a semiclassical approach, can also be identified directly from the dynamics. Our analysis of quantum tunneling is done with the effective flux of the Husimi volume of the evolved states between different regions of the phase space. Both initial coherent states and quench dynamics are considered. We argue that the level crossings and their consequences to the dynamics are typical to any quantum system with one degree of freedom, whose density of states presents a local logarithmic divergence and a local step discontinuity.Comment: 13 pages, 8 figure

VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory

VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l. in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design, construction techniques and data acquisition system of the HAWC observatory. HAWC is an air-shower array currently under construction at the same site of VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water Cherenkov detectors and two different data acquisition systems. It was in operation between October 2011 and May 2012 with an average live time of 30%. Besides the scientific verification purposes, the eight months of data were used to obtain the results presented in this paper: the detector response to the Forbush decrease of March 2012, and the analysis of possible emission, at energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages, 10 figures). Corresponding authors: A.Marinelli and D.Zaboro

Open Ocean Deep Sea

The deep sea comprises the seafloor, water column and biota therein below aspecified depth contour. There are differences in views among experts and agencies regarding the appropriate depth to delineate the “deep sea”. This chapter uses a 200 metre depth contour as a starting point, so that the “deep sea” represents 63 per cent of the Earth’s surface area and about 98.5 per cent of Earth’s habitat volume (96.5 per cent of which is pelagic). However, much of the information presented in this chapter focuses on biodiversity of waters substantially deeper than 200 m. Many of the other regional divisions of Chapter 36 include treatments of shelf and slope biodiversity in continental-shelf and slope areas deeper than 200m. Moreover Chapters 42 and 45 on coldwater corals and vents and seeps, respectively, and 51 on canyons, seamounts and other specialized morphological habitat types address aspects of areas in greater detail. The estimates of global biodiversity of the deep sea in this chapter do include all biodiversity in waters and the seafloor below 200 m. However, in the other sections of this chapter redundancy with the other regional chapters is avoided, so that biodiversity of shelf, slope, reef, vents, and specialized habitats is assessed in the respective regional or thematic chapters. AB - The deep sea comprises the seafloor, water column and biota therein below aspecified depth contour. There are differences in views among experts and agencies regarding the appropriate depth to delineate the “deep sea”. This chapter uses a 200 metre depth contour as a starting point, so that the “deep sea” represents 63 per cent of the Earth’s surface area and about 98.5 per cent of Earth’s habitat volume (96.5 per cent of which is pelagic). However, much of the information presented in this chapter focuses on biodiversity of waters substantially deeper than 200 m. Many of the other regional divisions of Chapter 36 include treatments of shelf and slope biodiversity in continental-shelf and slope areas deeper than 200m. Moreover Chapters 42 and 45 on coldwater corals and vents and seeps, respectively, and 51 on canyons, seamounts and other specialized morphological habitat types address aspects of areas in greater detail. The estimates of global biodiversity of the deep sea in this chapter do include all biodiversity in waters and the seafloor below 200 m. However, in the other sections of this chapter redundancy with the other regional chapters is avoided, so that biodiversity of shelf, slope, reef, vents, and specialized habitats is assessed in the respective regional or thematic chapters.https://nsuworks.nova.edu/occ_facbooks/1050/thumbnail.jp

Human immunodeficiency virus/hepatits C virus coinfection in Spain: Elimination is feasible, but the burden of residual cirrhosis will be significant

Background We assessed the prevalence of antibodies against hepatitis C virus (HCV-Abs) and active HCV infection in patients infected with human immunodeficiency virus (HIV) in Spain in 2016 and compared the results with those of similar studies performed in 2002, 2009, and 2015. Methods The study was performed in 43 centers during October-November 2016. The sample was estimated for an accuracy of 2% and selected by proportional allocation and simple random sampling. During 2016, criteria for therapy based on direct-acting antiviral agents (DAA) were at least significant liver fibrosis, severe extrahepatic manifestations of HCV, and high risk of HCV transmissibility. Results The reference population and the sample size were 38904 and 1588 patients, respectively. The prevalence of HCV-Abs in 2002, 2009, 2015, and 2016 was 60.8%, 50.2%, 37.7%, and 34.6%, respectively (P trend <.001, from 2002 to 2015). The prevalence of active HCV in 2002, 2009, 2015, and 2016 was 54.0%, 34.0%, 22.1%, and 11.7%, respectively (P trend <.001). The anti-HCV treatment uptake in 2002, 2009, 2015, and 2016 was 23.0%, 48.0%, 59.3%, and 74.7%, respectively (P trend <.001). In 2016, HCV-related cirrhosis was present in 7.6% of all HIV-infected individuals, 15.0% of patients with active HCV, and 31.5% of patients who cleared HCV after anti-HCV therapy. Conclusions Our findings suggest that with universal access to DAA-based therapy and continued efforts in prevention and screening, it will be possible to eliminate active HCV among HIV-infected individuals in Spain in the short term. However, the burden of HCV-related cirrhosis will continue to be significant among HIV-infected individuals

Chromatin regulation by Histone H4 acetylation at Lysine 16 during cell death and differentiation in the myeloid compartment

Histone H4 acetylation at Lysine 16 (H4K16ac) is a key epigenetic mark involved in gene regulation, DNA repair and chromatin remodeling, and though it is known to be essential for embryonic development, its role during adult life is still poorly understood. Here we show that this lysine is massively hyperacetylated in peripheral neutrophils. Genome-wide mapping of H4K16ac in terminally differentiated blood cells, along with functional experiments, supported a role for this histone post-translational modification in the regulation of cell differentiation and apoptosis in the hematopoietic system. Furthermore, in neutrophils, H4K16ac was enriched at specific DNA repeats. These DNA regions presented an accessible chromatin conformation and were associated with the cleavage sites that generate the 50 kb DNA fragments during the first stages of programmed cell death. Our results thus suggest that H4K16ac plays a dual role in myeloid cells as it not only regulates differentiation and apoptosis, but it also exhibits a non-canonical structural role in poising chromatin for cleavage at an early stage of neutrophil cell death