593 research outputs found
Investigation of IBMQ quantum device hardware calibration with Markovian master equation.
Masters Degree. University of KwaZulu-Natal. Durban.In the design of quantum technology, it is crucial to account for the quantum system interacting
with its environment to understand the influence of thermal processes and design the
devices to avoid eâ”ects of relaxation and decoherence of quantum states deteriorating the
system beyond use. To accomplish this, a broadening of ideal isolated quantum mechanics
is required, namely the theory of open quantum systems. This is most prevalent in the
research of quantum error correction, which ensures that the initial quantum state remains
intact when it is received and doesnât decay into a diâ”erent state which would change the
information carried by the qubit. To investigate the intersection of all these phenomena,
open-access cloud-computing services oâ”er the ideal experimental environment. One such
test-bed is oâ”ered by IBM in their Quantum Experience platform which allows for remote
access to quantum devices. The IBMQ quantum processors, which make use of superconducting
qubit technology, are openly accessible through a cloud service. As such, they have
been the focus of a lot of research into the evolution of quantum states while interacting
with the environment. In the study of open quantum systems, an assumption is often
made that the system and environment share no memory of the interaction of individual
quantum states, which simplifies the analysis of the systemâs evolution while also being
eâ”ectively true for large enough systems. Systems that obey this assumption are known
as Markovian. New research has devised methods of error correction and tomography of
quantum processors when this assumption no longer holds. Additionally, the calibration
of the IBMQ processors performed by IBM to provide hardware parameters is performed
through a set of techniques that are not guaranteed to yield cohesive results. These primary
factors, among others, give rise to the research discussed in this dissertation, and
pose the question of how accurate the hardware calibrations are when compared to results
obtained through experiments performed on the devices. Furthermore, the approach uses
the theory of open quantum systems to assess the hardware calibration while also testing
whether the Markovian assumption of a memoryless system holds for the IBMQ quantum
devices. This gives insight into the current state of superconducting quantum computers
while providing a possible new avenue for quantum error correction from the perspective
of the theory of open quantum systems.Publications listed on page iv
SLS-Derived Lab: Precursor to Deep Space Human Exploration
Plans to send humans to Mars are in work and the launch system is being built. Are we ready? Robotic missions have successfully demonstrated transportation, entry, landing and surface operations but for human missions there are significant, potentially show-stopping issues. These issues, called Strategic Knowledge Gaps (SKGs) are the unanswered questions concerning long-duration exploration beyond low-earth-orbit. The gaps represent a risk of loss of life or mission and because they require extended exposure to the weightless environment outside earth's protective geo-magnetic field they cannot be resolved on the earth or on the International Space Station (ISS). Placing a laboratory at the relatively close and stable lunar Distant Retrograde Orbit (DRO) provides an accessible location with the requisite environmental conditions for conducting SKG research and testing mitigation solutions. Configurations comprised of multiple 3 meter and 4.3 meter diameter modules have been studied but the most attractive solution uses elements of the human Mars launch vehicle or Space Launch System (SLS) for a Mars proving ground laboratory. A shortened version of an SLS hydrogen propellant tank creates a Skylab-like pressure vessel that flies fully outfitted on a single launch. This not only offers significant savings by incorporating SLS pressure vessel development costs but avoids the expensive ISS approach using many launches with substantial on-orbit assembly before becoming operational. One of the most challenging SKGs is crew radiation protection; this is why SKG laboratory research is combined with Mars transit Habitat systems development. Fundamentally, the two cannot be divorced because using the habitat systems for protection requires actual hardware geometry and material properties intended to contribute to shielding effectiveness. The SKGs are difficult problems, solutions are not obvious, and require integrated, iterative, and multi-disciplinary development. A lunar DRO lab built from the launch system elements enables an early and representative transit habitat test bed necessary for closing gaps before sending humans on a 1000 day Mars mission
SLS-Derived Lab- Precursor to Deep Space Human Exploration
Plans to send humans to Mars are in the works and the launch system is being built. Are we ready? Transportation, entry, landing, and surface operations have been successfully demonstrated for robotic missions. However, for human missions, there are significant, potentially show-stopping issues. These issues, called Strategic Knowledge Gaps (SKGs), are the unanswered questions concerning long duration exploration Beyond low Earth Orbit (BEO). The gaps represent a risk of loss of life or mission and because they require extended exposure to the weightless environment outside of earth's protective geo-magnetic field, they cannot be resolved on Earth or on the International Space Station (ISS). Placing a laboratory at a relatively close and stable lunar Distant Retrograde Orbit (DRO) provides an accessible location with the requisite environmental conditions for conducting SKG research and testing mitigation solutions. Configurations comprised of multiple 3 m and 4.3 m diameter modules have been studied but the most attractive solution uses elements of the human Mars launch vehicle or Space Launch System (SLS) for a Mars proving ground laboratory. A shortened version of an SLS hydrogen propellant tank creates a Skylab-like pressure vessel that flies fully outfitted on a single launch. This not only offers significant savings by incorporating SLS pressure vessel development costs but avoids the expensive ISS approach using many launches with substantial on-orbit assembly before becoming operational. One of the most challenging SKGs is crew radiation protection; this is why SKG laboratory research is combined with Mars transit habitat systems development. Fundamentally, the two cannot be divorced because using the habitat systems for protection requires actual hardware geometry and material properties intended to contribute to shielding effectiveness. The SKGs are difficult problems. The solutions to these problems are not obvious; they require integrated, iterative, and multi-disciplinary development. A lunar DRO lab built from SLS elements enables an early and representative transit habitat test bed necessary for closing gaps before sending humans on a 1,000-day Mars mission
Bounded seas
Abstract Imprecise manipulation of source code (semi-parsing) is useful for tasks such as robust parsing, error recovery, lexical analysis, and rapid development of parsers for data extraction. An island grammar precisely defines only a subset of a language syntax (islands), while the rest of the syntax (water) is defined imprecisely. Usually water is defined as the negation of islands. Albeit simple, such a definition of water is naive and impedes composition of islands. When developing an island grammar, sooner or later a language engineer has to create water tailored to each individual island. Such an approach is fragile, because water can change with any change of a grammar. It is time-consuming, because water is defined manually by an engineer and not automatically. Finally, an island surrounded by water cannot be reused because water has to be defined for every grammar individually. In this paper we propose a new technique of island parsing â- bounded seas. Bounded seas are composable, robust, reusable and easy to use because island-specific water is created automatically. Our work focuses on applications of island parsing to data extraction from source code. We have integrated bounded seas into a parser combinator framework as a demonstration of their composability and reusability
Note and Comment
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Amplitude equations for a system with thermohaline convection
The multiple scale expansion method is used to derive amplitude equations for
a system with thermohaline convection in the neighborhood of Hopf and Taylor
bifurcation points and at the double zero point of the dispersion relation. A
complex Ginzburg-Landau equation, a Newell-Whitehead-type equation, and an
equation of the type, respectively, were obtained. Analytic
expressions for the coefficients of these equations and their various
asymptotic forms are presented. In the case of Hopf bifurcation for low and
high frequencies, the amplitude equation reduces to a perturbed nonlinear
Schr\"odinger equation. In the high-frequency limit, structures of the type of
"dark" solitons are characteristic of the examined physical system.Comment: 21 pages, 8 figure
A scalable system to measure contrail formation on a per-flight basis
Persistent contrails make up a large fraction of aviation's contribution to
global warming. We describe a scalable, automated detection and matching (ADM)
system to determine from satellite data whether a flight has made a persistent
contrail. The ADM system compares flight segments to contrails detected by a
computer vision algorithm running on images from the GOES-16 Advanced Baseline
Imager. We develop a 'flight matching' algorithm and use it to label each
flight segment as a 'match' or 'non-match'. We perform this analysis on 1.6
million flight segments. The result is an analysis of which flights make
persistent contrails several orders of magnitude larger than any previous work.
We assess the agreement between our labels and available prediction models
based on weather forecasts. Shifting air traffic to avoid regions of contrail
formation has been proposed as a possible mitigation with the potential for
very low cost/ton-CO2e. Our findings suggest that imperfections in these
prediction models increase this cost/ton by about an order of magnitude.
Contrail avoidance is a cost-effective climate change mitigation even with this
factor taken into account, but our results quantify the need for more accurate
contrail prediction methods and establish a benchmark for future development.Comment: 25 pages, 6 figure
Reporters for the analysis of N-glycosylation in Candida albicans
Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.Peer reviewedPublisher PD
Discovery of a young massive stellar cluster near HESS J1813-178
We present the serendipitous discovery of a young stellar cluster in the
Galactic disk at l=12deg. Using Keck/NIRSPEC, we obtained high- and
low-resolution spectroscopy of several stars in the cluster, and we identified
one red supergiant and two blue supergiants. The radial velocity of the red
supergiant provides a kinematic cluster distance of 4.7pm0.4 kpc, implying
luminosities of the stars consistent with their spectral types. Together with
the known Wolf-Rayet star located 2.4' from the cluster center, the presence of
the red supergiant and the blue supergiants suggests a cluster age of 6-8 Myr,
and an initial mass of 2000 Msun. Several stars in the cluster are coincident
with X-ray sources, including the blue supergiants and the Wolf-Rayet star.
This is indicative of a high binary fraction, and is reminiscent of the massive
young cluster Westerlund 1. The cluster is coincident with two supernova
remnants, SNR G12.72-0.0 and G12.82-0.02, and the highly magnetized pulsar
associated with the TeV gamma-ray source HESS J1813-178. The mixture of
spectral types suggests that the progenitors of these objects had initial
masses of 20 - 30 Msun.Comment: 4 pages, 3 figures. ApJ Letter, accepted. Figure 2 has been revise
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