3,279 research outputs found
Post-Quantum Key Agreement Protocol based on Non-Square Integer Matrices
We present in this paper an algorithm for exchanging session keys, coupled
with a hashing encryption module. We show schemes designed for their potential
invulnerability to classical and quantum attacks. In turn, if the parameters
included were appropriate, brute-force attacks exceed the (five) security
levels used in the NIST competition of new post-quantum standards. The original
idea consists of products of rectangular matrices in Zp as public values and
whose factorization is proved to be an NP-complete problem. We present running
times as a function of the explored parameters and their link with operational
safety. To our knowledge there are no classical and quantum attacks of
polynomial complexity available at hand, remaining only the systematic
exploration of the private-key space.Comment: 12 pages, 2 tables, 29 reference
Laser Technologies for Applications in Quantum Information Science
Scientific progress in experimental physics is inevitably dependent on continuing advances in the underlying technologies. Laser technologies enable controlled coherent and dissipative atom-light interactions and micro-optical technologies allow for the implementation of versatile optical systems not accessible with standard optics.
This thesis reports on important advances in both technologies with targeted applications ranging from Rydberg-state mediated quantum simulation and computation with individual atoms in arrays of optical tweezers to high-resolution spectroscopy of highly-charged ions.
A wide range of advances in laser technologies are reported: The long-term stability and maintainability of external-cavity diode laser systems is improved significantly by introducing a mechanically adjustable lens mount. Tapered-amplifier modules based on a similar lens mount are developed. The diode laser systems are complemented by digital controllers for laser frequency and intensity stabilisation. The controllers offer a bandwidth of up to 1.25 MHz and a noise performance set by the commercial STEMlab platform. In addition, shot-noise limited photodetectors optimised for intensity stabilisation and Pound-Drever-Hall frequency stabilisation as well as a fiber based detector for beat notes in the MHz-regime are developed. The capabilities of the presented techniques are demonstrated by analysing the performance of a laser system used for laser cooling of Rb85 at a wavelength of 780 nm. A reference laser system is stabilised to a spectroscopic reference provided by modulation transfer spectroscopy. This spectroscopy scheme is analysed finding optimal operation at high modulation indices. A suitable signal is generated with a compact and cost-efficient module. A scheme for laser offset-frequency stabilisation based on an optical phase-locked loop is realised. All frequency locks derived from the reference laser system offer a Lorentzian linewidth of 60 kHz (FWHM) in combination with a long-term stability of 130 kHz peak-to-peak within 10 days. Intensity stabilisation based on acousto-optic modulators in combination with the digital controller allows for real-time intensity control on microsecond time scales complemented by a sample and hold feature with a response time of 150 ns.
High demands on the spectral properties of the laser systems are put forward for the coherent excitation of quantum states. In this thesis, the performance of active frequency stabilisation is enhanced by introducing a novel current modulation technique for diode lasers. A flat response from DC to 100 MHz and a phase lag below 90° up to 25 MHz are achieved extending the bandwidth available for laserfrequency stabilisation. Applying this technique in combination with a fast proportional-derivative controller, two laser fields with a relative phase noise of 42 mrad for driving rubidium ground state transitions are realised. A laser system for coherent Rydberg excitation via a two-photon scheme provides light at 780 nm and at 480 nm via frequency-doubling from 960 nm. An output power of 0.6 W at 480 nm from a single-mode optical fiber is obtained . The frequencies of both laser systems are stabilised to a high-finesse reference cavity resulting in a linewidth of 1.02 kHz (FWHM) at 960 nm. Numerical simulations quantify the effect of the finite linewidth on the coherence of Rydberg Rabi-oscillations. A laser system similar to the 480 nm Rydberg system is developed for spectroscopy on highly charged bismuth.
Advanced optical technologies are also at the heart of the micro-optical generation of tweezer arrays that offer unprecedented scalability of the system size. By using an optimised lens system in combination with an automatic evaluation routine, a tweezer array with several thousand sites and trap waists below 1 μm is demonstrated. A similar performance is achieved with a microlens array produced in an additive manufacturing process. The microlens design is optimised for the manufacturing process. Furthermore, scattering rates in dipole traps due to suppressed resonant light are analysed proving the feasibility of dipole trap generation using tapered amplifier systems
Oka tubes in holomorphic line bundles
Let be a positive holomorphic line bundle on a Grassmann manifold of
dimension . We show that for every semipositive hermitian metric on
, the disc bundle is an Oka manifold, while
the complementary tube
is pseudoconvex and Kobayashi hyperbolic. When the base manifold is a
projective space, we also show that the punctured disc bundle
is an Oka manifold. These phenomena
contribute to the heuristic principle that Oka properties are related to metric
positivity of complex manifolds
Asymptotic analysis of Emden–Fowler type equation with an application to power flow models
Emden–Fowler type equations are nonlinear differential equations that appear in many fields such as mathematical physics, astrophysics and chemistry. In this paper, we perform an asymptotic analysis of a specific Emden–Fowler type equation that emerges in a queuing theory context as an approximation of voltages under a well-known power flow model. Thus, we place Emden–Fowler type equations in the context of electrical engineering. We derive properties of the continuous solution of this specific Emden–Fowler type equation and study the asymptotic behavior of its discrete analog. We conclude that the discrete analog has the same asymptotic behavior as the classical continuous Emden–Fowler type equation that we consider.</p
Computational Approaches to Drug Profiling and Drug-Protein Interactions
Despite substantial increases in R&D spending within the pharmaceutical industry, denovo drug design has become a time-consuming endeavour. High attrition rates led to a
long period of stagnation in drug approvals. Due to the extreme costs associated with
introducing a drug to the market, locating and understanding the reasons for clinical failure
is key to future productivity. As part of this PhD, three main contributions were made in
this respect. First, the web platform, LigNFam enables users to interactively explore
similarity relationships between ‘drug like’ molecules and the proteins they bind. Secondly,
two deep-learning-based binding site comparison tools were developed, competing with
the state-of-the-art over benchmark datasets. The models have the ability to predict offtarget interactions and potential candidates for target-based drug repurposing. Finally, the
open-source ScaffoldGraph software was presented for the analysis of hierarchical scaffold
relationships and has already been used in multiple projects, including integration into a
virtual screening pipeline to increase the tractability of ultra-large screening experiments.
Together, and with existing tools, the contributions made will aid in the understanding of
drug-protein relationships, particularly in the fields of off-target prediction and drug
repurposing, helping to design better drugs faster
Carbon-Free Power
There is a new world order in electrical energy production. Solar and wind power are established as the low-cost leaders. However, these energy sources are highly variable and electrical power is needed 24/7. Alternative sources must fill the gaps, but only a few are both economical and carbon-free or -neutral.
This book presents one alternative: small modular nuclear reactors (SMRs). The authors describe the technology, including its safety and economic aspects, and assess its fit with other carbon-free energy sources, storage solutions, and industrial opportunities. They also explain the challenges with SMRs, including public acceptance.
The purpose of the book is to help readers consider these relatively new reactors as part of an appropriate energy mix for the future and, ultimately, to make their own judgments on the merits of the arguments for SMRs.Publishe
On the Aggregation of Rules for Knowledge Graph Completion
Rule learning approaches for knowledge graph completion are efficient,
interpretable and competitive to purely neural models. The rule aggregation
problem is concerned with finding one plausibility score for a candidate fact
which was simultaneously predicted by multiple rules. Although the problem is
ubiquitous, as data-driven rule learning can result in noisy and large
rulesets, it is underrepresented in the literature and its theoretical
foundations have not been studied before in this context. In this work, we
demonstrate that existing aggregation approaches can be expressed as marginal
inference operations over the predicting rules. In particular, we show that the
common Max-aggregation strategy, which scores candidates based on the rule with
the highest confidence, has a probabilistic interpretation. Finally, we propose
an efficient and overlooked baseline which combines the previous strategies and
is competitive to computationally more expensive approaches.Comment: KLR Workshop@ICML202
COVID 19 effect on mental health
A cross-sectional study was conducted to evaluate the severity of anxiety among medical students due to COVID-19. The study was conducted from June, 2020 to July, 2020 at Ayub Medical College, Abbottabad, Pakistan. The target population was MBBS students from all 5 years of study.We calculated the sample size using the formula n = z2 * p * (1 - p) / e2, where n is the sample size, z is the standard normal deviate corresponding to the confidence level (1.96 for 95%), and e is the desired precision (0.05). We used the p as 0.34, using a meta-analysis that concluded that 34% of the medical students globally had anxiety as the value of p and obtained a sample size of 344. However, due to time and resource constraints, we selected 200 as the size.We obtained a list of all enrolled medical students from the college administration assigned each student a unique number. We used a random number generator to select 344 students. We approached the selected students and recruited volunteers until the total number reached 200. The response rate 60%. The sample was representative of the target population in terms of gender, age, and year of study. The inclusion criteria for our study were that participants were enrolled in the MBBS program at Ayub Medical College, Abbottabad, Pakistan, and that they were willing to complete the study questionnaire.Verbal consent was obtained from all participants before they completed the questionnaire. They were informed about the purpose, procedures, risks, and benefits of the study, as well as their right to withdraw at any time. They were also assured that their responses would be kept confidential and anonymous. A questionnaire was distributed to the students, which included 8 questions about their demographics, while in the second part we used GAD-7 (generalized anxiety disorder-7) to measure their levels of anxiety. GAD-7 asks 7 questions where the responses are quantified from 1 to 4. The range of the total score can be from 0 to 21. An additional variable named “levels of anxiety” was created in SPSS to translate the total score to either “minimal”, “mild”, “moderate” or “severe” anxiety. Both data entry and analysis were done in SPSS version 26. Categorical variables from demographics were described as “frequency” and “frequency percentage”, while quantitative variables were defined as “mean”, “standard deviation” and “range (Maximum and minimum)”. The results of the responses to GAD-7 were reported as frequencies of students whose scores were represented according to the previously described variable “levels of anxiety”. Potential sources of bias were addressed by stratifying the sample by gender, marital status, having a supportive roommate, family income, year of study, and anxiety history, and testing the association between each factor and levels of anxiety using chi-squared tests. A p-value of less than or equal 0.05 was set as the threshold for the test of significance.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
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