1,318 research outputs found
Highly Reliable and Repeatable Soldering Technique for Assembling Empty Substrate Integrated Waveguide Devices
[EN] In this paper, a novel mymargin soldering technique that improves the fabrication process of empty substrate integrated waveguide (ESIW) devices is presented. Up until now, in order to fabricate an ESIW device, the tin solder paste was distributed, before assembling, on the contact surface between layers, in order to ensure a good electrical contact. This process has a low degree of repeatability (random soldering thickness and distribution of tin) and reliability (a significant number of nonworking prototypes due to tin overflow). In this paper, we propose the mechanization of a set of plated vias just next to the metalized walls of the ESIW in the central layer. Next, in the top and bottom covers that close this ESIW, additional plated vias are drilled in the same position so that, when the device is assembled (using screws or rivets), metalized holes can be seen passing through the whole structure from top to bottom. These holes are then used as soldering vias that can guide the tin paste straight to the point where it is needed. When the paste is dried, soldered vias ensure a very good electrical contact between layers. In addition, the fluid tin fills any small gap that appears between layers, thus providing a very good electrical contact and mechanical union. This novel soldering technique has been validated with experimental results. Several prototypes of filters centered at 13 and 35 GHz have been fabricated, proving the repeatability and reliability of the proposed soldering technique.This work was supported by the Ministerio de Economiy Competitividad, Spanish Government, under Project TEC2016-75934-C4-3-R and Project TEC2016-75934-C4-1-R.Martinez, JA.; Belenguer, A.; Esteban González, H. (2019). Highly Reliable and Repeatable Soldering Technique for Assembling Empty Substrate Integrated Waveguide Devices. IEEE Transactions on Components, Packaging and Manufacturing Technology (Online). 9(11):2276-2281. https://doi.org/10.1109/TCPMT.2019.2915688S2276228191
Hole spin driving by strain-induced spin-orbit interactions
Hole spins in semiconductor quantum dots can be efficiently manipulated with
radio-frequency electric fields owing to the strong spin-orbit interactions in
the valence bands. Here we show that the motion of the dot in inhomogeneous
strain fields gives rise to linear Rashba spin-orbit interactions (with
spatially dependent spin-orbit lengths) and g-factor modulations that allow for
fast Rabi oscillations. Such inhomogeneous strains may build up spontaneously
due to process and cool down stress. We discuss spin qubits in Ge/GeSi
heterostructures as an illustration. We highlight that Rabi frequencies can be
enhanced by one order of magnitude by shear strain gradients as small as
nm within the dots. This underlines that spin in
solids can be very sensitive to strains and opens the way for strain
engineering in hole spin devices for quantum information and spintronics.Comment: 19 pages, 3 figure
Dynamics and thermodynamics of linear quantum open systems
We analyze the behavior of a network of quantum oscillators coupled with a
number of external environments. We show that the dynamics is such that the
quantum state of the network always obeys a local master equation with a simple
analytical solution. We use this to study the emergence of thermodynamical laws
in the stationary regime, achieved for sufficiently long times if the
environments are dissipative. We show that the validity of the second law
implies the impossibility of building a quantum refrigerator without moving
parts (therefore, a quantum absorption refrigerators requires non-linearity as
an crucial ingredient, as recently proposed by Kosloff and others
cite{Kosloff1,Kosloff2}). We also show that the third law imposes strong
constraints on the low frequency behavior of the environmental spectral
densities.Comment: 4 pages of main text, 6 pages of supplementary material, 1 figure;
substantially modified, detailed derivations presented in the supplementary
materia
Hole spin manipulation in inhomogeneous and non-separable electric fields
The usual models for electrical spin manipulation in semiconductor quantum
dots assume that the confinement potential is separable in the three spatial
dimensions and that the AC drive field is homogeneous. However, the electric
field induced by the gates in quantum dot devices is not fully separable and
displays significant inhomogeneities. Here, we address the electrical
manipulation of hole spins in semiconductor heterostructures subject to
inhomogeneous vertical electric fields and/or in-plane AC electric fields. We
consider Ge quantum dots electrically confined in a Ge/GeSi quantum well as an
illustration. We show that the lack of separability between the vertical and
in-plane motions gives rise to an additional spin-orbit coupling mechanism
(beyond the usual linear and cubic in momentum Rashba terms) that modulates the
principal axes of the hole gyromagnetic g-matrix. This non-separability
mechanism can be of the same order of magnitude as Rashba-type interactions,
and enables spin manipulation when the magnetic field is applied in the plane
of the heterostructure even if the dot is symmetric (disk-shaped). More
generally, we show that Rabi oscillations in strongly patterned electric fields
harness a variety of g-factor modulations. We discuss the implications for the
design, modeling and understanding of hole spin qubit devices
Effect of resistance training and hypocaloric diets with different protein content on body composition and lipid profile in hypercholesterolemic obese women
Lifestyle changes such as following a hypocaloric diet and regular physical exercise are recognized as effective non-pharmacological interventions to reduce body fat mass and prevent cardiovascular disease risk factors. Purpose: To evaluate the interactions of a higher protein (HP) vs. a lower protein (LP) diet with or without a concomitant progressive resistance training program (RT) on body composition and lipoprotein profile in hypercholesterolemic obese women. Methods: Retrospective study derived from a 16-week randomized controlled-intervention clinical trial. Twentyfive sedentary, obese (BMI: 30-40 kg/m²) women, aged 40-60 with hypercholesterolemia were assigned to a 4-arm trial using a 2 x 2 factorial design (Diet x Exercise). Prescribed diets had the same calorie restriction (-500 kcal/day), and were categorized according to protein content as: lower protein ( 22% daily energy intake, HP). Exercise comparisons involved habitual activity (control) vs. a 16-week supervised whole-body resistance training program (RT), two sessions/wk. Results: A significant decrease in weight and waist circumference was observed in all groups. A significant decrease in LDL-C and Total-Cholesterol levels was observed only when a LP diet was combined with a RT program, the RT being the most determining factor. Interestingly, an interaction between diet and exercise was found concerning LDL-C values. Conclusion: In this study, resistance training plays a key role in improving LDL-C and Total-Cholesterol; however, a lower protein intake (< 22% of daily energy intake as proteins) was found to achieve a significantly greater reduction in LDL-C
Characterizing large-scale quantum computers via cycle benchmarking
Quantum computers promise to solve certain problems more efficiently than
their digital counterparts. A major challenge towards practically useful
quantum computing is characterizing and reducing the various errors that
accumulate during an algorithm running on large-scale processors. Current
characterization techniques are unable to adequately account for the
exponentially large set of potential errors, including cross-talk and other
correlated noise sources. Here we develop cycle benchmarking, a rigorous and
practically scalable protocol for characterizing local and global errors across
multi-qubit quantum processors. We experimentally demonstrate its practicality
by quantifying such errors in non-entangling and entangling operations on an
ion-trap quantum computer with up to 10 qubits, with total process fidelities
for multi-qubit entangling gates ranging from 99.6(1)% for 2 qubits to 86(2)%
for 10 qubits. Furthermore, cycle benchmarking data validates that the error
rate per single-qubit gate and per two-qubit coupling does not increase with
increasing system size.Comment: The main text consists of 6 pages, 3 figures and 1 table. The
supplementary information consists of 6 pages, 2 figures and 3 table
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