46 research outputs found
The Lerch Zeta Function II. Analytic Continuation
This is the second of four papers that study algebraic and analytic
structures associated with the Lerch zeta function. In this paper we
analytically continue it as a function of three complex variables. We that it
is well defined as a multivalued function on the manifold M equal to C^3 with
the hyperplanes corresponding to integer values of the two variables a and c
removed. We show that it becomes single valued on the maximal abelian cover of
M. We compute the monodromy functions describing the multivalued nature of this
function on M, and determine various of their properties.Comment: 29 pages, 3 figures; v2 notation changes, homotopy action on lef
Phononic bath engineering of a superconducting qubit
Phonons, the ubiquitous quanta of vibrational energy, play a vital role in
the performance of many quantum technologies. Coupling to well-defined phonon
modes allows for highly-connected multi-qubit gates in ion trap architectures
as well as the generation of entangled states in systems of superconducting
qubits. Even when the phonons take the form of a large dissipative bath, an
irreversible flow of heat allows for state initialization critical to the
function of laser systems and the operation of optically active spin qubits.
Conversely, unintended coupling to phonons has been shown to degrade qubit
performance by generating decohering quasiparticles and leading to correlated
errors in superconducting qubit systems. Regardless of whether a phononic bath
plays an enabling or deleterious role, it is typically intrinsic to the system
and does not admit specific control over its spectral properties, nor the
possibility of engineering aspects of its dissipation to be used as a resource.
Here we show that by precisely designing and controlling the coupling of a
superconducting qubit to phononic degrees of freedom allows a new type of
quantum control over superconducting circuits. By shaping the loss spectrum of
the qubit via its coupling to a bath of lossy piezoelectric surface acoustic
wave phonons, we are able to prepare and stabilize arbitrary qubit states.
Additionally, we find that the presence of the energy-dependent loss imparted
onto the qubit by the phonons is well-described by a master equation treatment
of the composite system, with excellent agreement in both the qubit dynamics as
well as its steady state. Our results demonstrate the ability of engineered
phononic dissipation to achieve highly efficient qubit control.Comment: 18 pages, 5 figures, 1 table, main text and S
Free-space coupling and characterization of transverse bulk phonon modes in a quantum acoustic device
Transverse bulk phonons in a multimode integrated quantum acoustic device are
excited and characterized via their free-space coupling to a three-dimensional
(3D) microwave cavity. These bulk acoustic modes are defined by the geometry of
the Y-cut lithium niobate substrate in which they reside and couple to the
cavity electric field via a large dipole antenna, with an interaction strength
on the order of the cavity line-width. Using finite element modeling (FEM) we
determine that the bulk phonons excited by the cavity field have a transverse
polarization with a shear velocity matching previously reported values. We
demonstrate how the coupling between these transverse acoustic modes and the
electric field of the 3D cavity depends on the relative orientation of the
device dipole, with a coupling persisting to room temperature. Our study
demonstrates the versatility of 3D microwave cavities for mediating
contact-less coupling to quantum, and classical, piezoacoustic devices.Comment: 5 pages, 4 figure
Quantum acoustic Fano interference of surface phonons
Quantum acoustic systems, which integrate surface or bulk phonons with
superconducting qubits, offer a unique opportunity to investigate phononic
and processes in the quantum regime. In particular
the interaction between a superconducting qubit and a phononic oscillator
allows the qubit to sense the oscillator's excitation spectrum and underlying
interference effects. Here we present measurements revealing Fano interference
of a resonantly trapped piezoelectric surface acoustic wave (SAW) mode with a
broad continuum of surface phonons in a system consisting of a SAW resonator
coupled to a superconducting qubit. The experiments highlight the existence of
additional weakly coupled mechanical modes and their influence on the
qubit-phonon interaction and underscore the importance of phononic interference
in quantum acoustic architectures that have been proposed for quantum
information processing applications.Comment: 7 pages, 5 figures. Updated title and abstrac
Helium surface fluctuations investigated with superconducting coplanar waveguide resonator
Recent experiments on the coupling of the in-plane motional state of
electrons floating on the surface of liquid helium to a microwave resonator
have revealed the importance of helium surface fluctuations to the coherence of
this motion. Here we investigate these surface fluctuations by studying the
resonance properties of a superconducting coplanar waveguide (CPW) resonator
filled with superfluid helium, where a significant fraction of the resonator's
electromagnetic mode volume is coupled to the surface dynamics of the liquid.
We present preliminary results on real-time CPW resonator frequency shifts
driven by helium fluctuations, which are quantified via their power spectral
density and compared with measurements using a commercial accelerometer. We
find that a considerable contribution to the CPW resonator noise originates
from the mechanical vibrations of the helium surface generated by the pulse
tube (PT) cryocooler on the cryostat on which the experiments were performed.Comment: 10 pages, 3 figures. J. Low Temp. Phys. (2022
Structure of the mirror nuclei Be and B in a microscopic cluster model
The structure of the mirror nuclei Be and B is studied in a
microscopic and three-cluster model
using a fully antisymmetrized 9-nucleon wave function. The two-nucleon
interaction includes central and spin-orbit components and the Coulomb
potential. The ground state of Be is obtained accurately with the
stochastic variational method, while several particle-unbound states of both
Be and B are investigated with the complex scaling method.The
calculation for Be supports the recent identification for the existence of
two broad states around 6.5 MeV, and predicts the and
states at about 4.5 MeV and 8 MeV, respectively. The
similarity of the calculated spectra of Be and B enables one to
identify unknown spins and parities of the B states. Available data on
electromagnetic moments and elastic electron scatterings are reproduced very
well. The enhancement of the 1 transition of the first excited state in
Be is well accounted for. The calculated density of Be is found to
reproduce the reaction cross section on a Carbon target. The analysis of the
beta decay of Li to Be clearly shows that the wave function of Be
must contain a small component that cannot be described by the simple model. This small component can be well accounted for by extending a
configuration space to include the distortion of the -particle to
and partitions.Comment: 24 page
A unified treatment of single component replacement models
In this paper we discuss a general framework for single component replacement models. This framework is based on the regenerative structure of these models and by using results from renewal theory a unified presentation of the discounted and average finite and infinite horizon cost models is given. Finally, some well-known replacement models are discussed, and making use of the previous results an easy derivation of their cost functions is presented
Natural disturbance impacts on trade-offs and co-benefits of forest biodiversity and carbon
With accelerating environmental change, understanding forest disturbance impacts on trade-offs between biodiversity and carbon dynamics is of high socio-economic importance. Most studies, however, have assessed immediate or short-term effects of disturbance, while long-term impacts remain poorly understood. Using a tree-ring-based approach, we analysed the effect of 250 years of disturbances on present-day biodiversity indicators and carbon dynamics in primary forests. Disturbance legacies spanning centuries shaped contemporary forest co-benefits and trade-offs, with contrasting, local-scale effects. Disturbances enhanced carbon sequestration, reaching maximum rates within a comparatively narrow post-disturbance window (up to 50 years). Concurrently, disturbance diminished aboveground carbon storage, which gradually returned to peak levels over centuries. Temporal patterns in biodiversity potential were bimodal; the first maximum coincided with the short-term post-disturbance carbon sequestration peak, and the second occurred during periods of maximum carbon storage in complex old-growth forest. Despite fluctuating local-scale trade-offs, forest biodiversity and carbon storage remained stable across the broader study region, and our data support a positive relationship between carbon stocks and biodiversity potential. These findings underscore the interdependencies of forest processes, and highlight the necessity of large-scale conservation programmes to effectively promote both biodiversity and long-term carbon storage, particularly given the accelerating global biodiversity and climate crises
Exploratory study of ultraviolet B (UVB) radiation and age of onset of bipolar disorder
Background: Sunlight contains ultraviolet B (UVB) radiation that triggers the production of vitamin D by skin. Vitamin D has widespread effects on brain function in both developing and adult brains. However, many people live at latitudes (about > 40 N or S) that do not receive enough UVB in winter to produce vitamin D. This exploratory study investigated the association between the age of onset of bipolar I disorder and the threshold for UVB sufficient for vitamin D production in a large global sample. Methods: Data for 6972 patients with bipolar I disorder were obtained at 75 collection sites in 41 countries in both hemispheres. The best model to assess the relation between the threshold for UVB sufficient for vitamin D production and age of onset included 1 or more months below the threshold, family history of mood disorders, and birth cohort. All coefficients estimated at P ≤ 0.001. Results: The 6972 patients had an onset in 582 locations in 70 countries, with a mean age of onset of 25.6 years. Of the onset locations, 34.0% had at least 1 month below the threshold for UVB sufficient for vitamin D production. The age of onset at locations with 1 or more months of less than or equal to the threshold for UVB was 1.66 years younger. Conclusion: UVB and vitamin D may have an important influence on the development of bipolar disorder. Study limitations included a lack of data on patient vitamin D levels, lifestyles, or supplement use. More study of the impacts of UVB and vitamin D in bipolar disorder is needed to evaluate this supposition
ANN multiscale model of anti-HIV Drugs activity vs AIDS prevalence in the US at county level based on information indices of molecular graphs and social networks
[Abstract] This work is aimed at describing the workflow for a methodology that combines chemoinformatics and pharmacoepidemiology methods and at reporting the first predictive model developed with this methodology. The new model is able to predict complex networks of AIDS prevalence in the US counties, taking into consideration the social determinants and activity/structure of anti-HIV drugs in preclinical assays. We trained different Artificial Neural Networks (ANNs) using as input information indices of social networks and molecular graphs. We used a Shannon information index based on the Gini coefficient to quantify the effect of income inequality in the social network. We obtained the data on AIDS prevalence and the Gini coefficient from the AIDSVu database of Emory University. We also used the Balaban information indices to quantify changes in the chemical structure of anti-HIV drugs. We obtained the data on anti-HIV drug activity and structure (SMILE codes) from the ChEMBL database. Last, we used Box-Jenkins moving average operators to quantify information about the deviations of drugs with respect to data subsets of reference (targets, organisms, experimental parameters, protocols). The best model found was a Linear Neural Network (LNN) with values of Accuracy, Specificity, and Sensitivity above 0.76 and AUROC > 0.80 in training and external validation series. This model generates a complex network of AIDS prevalence in the US at county level with respect to the preclinical activity of anti-HIV drugs in preclinical assays. To train/validate the model and predict the complex network we needed to analyze 43,249 data points including values of AIDS prevalence in 2,310 counties in the US vs ChEMBL results for 21,582 unique drugs, 9 viral or human protein targets, 4,856 protocols, and 10 possible experimental measures.Ministerio de Educación, Cultura y Deportes; AGL2011-30563-C03-0