scholarly journals Time-optimal quantum transformations with bounded bandwidth

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 462
Author(s):  
Dan Allan ◽  
Niklas Hörnedal ◽  
Ole Andersson
Keyword(s):  
Final Section ◽  
Eigenvalue Spectrum ◽  
Speed Limits ◽  
Von Neumann ◽  
Average Value ◽  
Transformation Time ◽  
Time Optimal ◽  
Speed Up ◽  
Geometric Techniques ◽  
Uniformly Bounded

In this paper, we derive sharp lower bounds, also known as quantum speed limits, for the time it takes to transform a quantum system into a state such that an observable assumes its lowest average value. We assume that the system is initially in an incoherent state relative to the observable and that the state evolves according to a von Neumann equation with a Hamiltonian whose bandwidth is uniformly bounded. The transformation time depends intricately on the observable's and the initial state's eigenvalue spectrum and the relative constellation of the associated eigenspaces. The problem of finding quantum speed limits consequently divides into different cases requiring different strategies. We derive quantum speed limits in a large number of cases, and we simultaneously develop a method to break down complex cases into manageable ones. The derivations involve both combinatorial and differential geometric techniques. We also study multipartite systems and show that allowing correlations between the parts can speed up the transformation time. In a final section, we use the quantum speed limits to obtain upper bounds on the power with which energy can be extracted from quantum batteries.

scholarly journals Optimal and Perfectly Parallel Algorithms for On-demand Data-Flow Analysis

2020 ◽  
pp. 112-140 ◽  
Author(s):  
Krishnendu Chatterjee ◽  
Amir Kafshdar Goharshady ◽  
Rasmus Ibsen-Jensen ◽  
Andreas Pavlogiannis
Keyword(s):  
Data Flow ◽  
Flow Analysis ◽  
Demand Analysis ◽  
Finite Domain ◽  
Data Flow Analysis ◽  
On Demand ◽  
Time Optimal ◽  
Speed Up ◽  
Flow Functions ◽  
Flow Graphs

AbstractInterprocedural data-flow analyses form an expressive and useful paradigm of numerous static analysis applications, such as live variables analysis, alias analysis and null pointers analysis. The most widely-used framework for interprocedural data-flow analysis is IFDS, which encompasses distributive data-flow functions over a finite domain. On-demand data-flow analyses restrict the focus of the analysis on specific program locations and data facts. This setting provides a natural split between (i) an offline (or preprocessing) phase, where the program is partially analyzed and analysis summaries are created, and (ii) an online (or query) phase, where analysis queries arrive on demand and the summaries are used to speed up answering queries.In this work, we consider on-demand IFDS analyses where the queries concern program locations of the same procedure (aka same-context queries). We exploit the fact that flow graphs of programs have low treewidth to develop faster algorithms that are space and time optimal for many common data-flow analyses, in both the preprocessing and the query phase. We also use treewidth to develop query solutions that are embarrassingly parallelizable, i.e. the total work for answering each query is split to a number of threads such that each thread performs only a constant amount of work. Finally, we implement a static analyzer based on our algorithms, and perform a series of on-demand analysis experiments on standard benchmarks. Our experimental results show a drastic speed-up of the queries after only a lightweight preprocessing phase, which significantly outperforms existing techniques.

scholarly journals Speed management as a measure to improve road safety on Polish regional roads

2017 ◽  
Vol 43 (3) ◽  
pp. 29-42 ◽  
Author(s):  
Stanisław Gaca ◽  
Sylwia Pogodzińska
Keyword(s):  
Road Safety ◽  
Speed Limits ◽  
Speed Reduction ◽  
Average Speed ◽  
Traffic Calming ◽  
Management Measures ◽  
Speed Management ◽  
Speed Up ◽  
Road Segments ◽  
Local Speed

The article presents the issue of the implementation of speed management measures on regional roads, whose character requires the use of different solutions than those on national roads. The authors briefly described speed management measures, the conditions for their implementation and their effectiveness with reference to environmental conditions and road safety. The further part of the paper presents selected results of the authors' research into the speed on various road segments equipped with different speed management measures. The estimations were made as to the impact of local speed limits and traffic calming measures on drivers' behaviour in free flow conditions. This research found that the introduction of the local speed limits cause reduction in average speed and 85th percentile speed up to 11.9 km/h (14.4%) and 16.3 km/h (16.8%) respectively. These values are averaged in the tested samples. Speed reduction depends strongly on the value of the limit and local circumstances. Despite speed reduction, the share of drivers who do not comply with speed limits was still high and ranged from 43% in the case of a 70 km/h limit, up to 89% for a 40 km/h limit. As far as comprehensive traffic calming measures are concerned, results show decrease in average speed and 85th percentile speed up to 18.1 km/h and 20.8 km/h respectively. For some road segments, however, the values of average speed and 85th percentile speed increased. It confirms that the effectiveness of speed management measures is strongly determined by local circumstances.

Too Popular, Too Fast: Optimal Advertising and Entry Timing in Markets with Peer Influence

2021 ◽  
Author(s):  
Gila E. Fruchter ◽  
Ashutosh Prasad ◽  
Christophe Van den Bulte
Keyword(s):  
Peer Influence ◽  
Boundary Value ◽  
Unknown Boundary ◽  
Entry Costs ◽  
Optimal Advertising ◽  
Fast Solution ◽  
Time Optimal ◽  
Speed Up ◽  
Entry Timing ◽  
Solution Methodology

We study optimal advertising and entry timing decisions for a new product being sold in two-segment markets in which followers are positively influenced by elites, whereas elites are either unaffected or repulsed by product popularity among followers. Key decisions in such markets are not only how much to advertise in each segment over time but also when to enter the follower segment. We develop a continuous-time optimal control model to examine these issues. Analysis yields two sets of two-point boundary value problems where one set has an unknown boundary value condition that satisfies an algebraic equation. A fast solution methodology is proposed. Two main insights emerge. First, the optimal advertising strategy can be U-shaped, that is, decreasing at first to free-ride peer influence but increasing later on to thwart the repulsion influence of overpopularity causing disadoption. Second, in markets where cross-segment repulsion triggers disadoption, advertising is only moderately effective, and entry costs are high, managing both advertising and entry timing can result in significantly higher profits than managing only one of these levers. In markets without disadoption, with high advertising effectiveness or with low entry costs, in contrast, delaying entry may add little value if one already manages advertising optimally. This implies that purveyors of prestige or cool products need not deny followers access to their products in order to protect their profits, and can use advertising to speed up the democratization of consumption profitably. This paper was accepted by Juanjuan Zhang, marketing.

scholarly journals Enabling 3D-Liver Perfusion Mapping from MR-DCE Imaging Using Distributed Computing

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Benjamin Leporq ◽  
Sorina Camarasu-Pop ◽  
Eduardo E. Davila-Serrano ◽  
Frank Pilleul ◽  
Olivier Beuf
Keyword(s):  
Distributed Computing ◽  
Liver Perfusion ◽  
Reference Method ◽  
Free Breathing ◽  
Blood Pool ◽  
Average Value ◽  
Contrast Enhanced ◽  
Healthy Control ◽  
Speed Up ◽  
Dynamic Acquisition

An MR acquisition protocol and a processing method using distributed computing on the European Grid Infrastructure (EGI) to allow 3D liver perfusion parametric mapping after Magnetic Resonance Dynamic Contrast Enhanced (MR-DCE) imaging are presented. Seven patients (one healthy control and six with chronic liver diseases) were prospectively enrolled after liver biopsy. MR-dynamic acquisition was continuously performed in free-breathing during two minutes after simultaneous intravascular contrast agent (MS-325 blood pool agent) injection. Hepatic capillary system was modeled by a 3-parameters one-compartment pharmacokinetic model. The processing step was parallelized and executed on the EGI. It was modeled and implemented as a grid workflow using the Gwendia language and the MOTEUR workflow engine. Results showed good reproducibility in repeated processing on the grid. The results obtained from the grid were well correlated with ROI-based reference method ran locally on a personal computer. The speed-up range was 71 to 242 with an average value of 126. In conclusion, distributed computing applied to perfusion mapping brings significant speed-up to quantification step to be used for further clinical studies in a research context. Accuracy would be improved with higher image SNR accessible on the latest 3T MR systems available today.

The Study on Electronic Equipments Reliability Prediction Model

2012 ◽  
Vol 152-154 ◽  
pp. 1885-1890
Author(s):  
Zhi Xue Liu
Keyword(s):  
Distribution Function ◽  
Probability Distribution ◽  
Temperature Stress ◽  
Probability Distribution Function ◽  
Reliability Prediction ◽  
Operating Pressure ◽  
Average Value ◽  
Equipment Reliability ◽  
Speed Up ◽  
Pressure Changes

This paper mainly analyzes the two operating pressure changes have a major impact on electronic equipment reliability: temperature stress and humidity pressure. The average value of the products for the whole region failure rate of product use can forecast and speed up the test data and two functions: temperature and humidity probability distribution function and probability distribution function. Compared with the normal reliability prediction technology, the authors think that both sides of the area changes between pressure temperature stress and humidity the entire product business scope for more accurate prediction.

scholarly journals The Geometry of Speed Limiting Resources in Physical Models of Computation

2017 ◽  
Vol 28 (04) ◽  
pp. 321-333 ◽  
Author(s):  
Benjamin Russell ◽  
Susan Stepney
Keyword(s):  
Limited Resource ◽  
Minimum Time ◽  
Physical Models ◽  
Maximum Speed ◽  
Speed Limit ◽  
Physical Computation ◽  
Speed Limits ◽  
Models Of Computation ◽  
Special Cases ◽  
Time Optimal

We study the maximum speed of quantum computation and how it is affected by limitations on physical resources. We show how the resulting concepts generalize to a broader class of physical models of computation within dynamical systems and introduce a specific algebraic structure representing these speed limits. We derive a family of quantum speed limit results in resource-constrained quantum systems with pure states and a finite dimensional state space, by using a geometric method based on right invariant action functionals on [Formula: see text]. We show that when the action functional is bi-invariant, the minimum time for implementing any quantum gate using a potentially time-dependent Hamiltonian is equal to the minimum time when using a constant Hamiltonian, thus constant Hamiltonians are time optimal for these constraints. We give an explicit formula for the time in these cases, in terms of the resource constraint. We show how our method produces a rich family of speed limit results, of which the generalized Margolus–Levitin theorem and the Mandelstam–Tamm inequality are special cases. We discuss the broader context of geometric approaches to speed limits in physical computation, including the way geometric approaches to quantum speed limits are a model for physical speed limits to computation arising from a limited resource.

Usability Analysis of Udayana University SIMAK System Interface

2020 ◽  
Vol 8 (4) ◽  
pp. 487
Author(s):  
Made Harry Dananjaya Adiartika ◽  
Luh Gede Astuti
Keyword(s):  
Vital Role ◽  
Management Information ◽  
Academic Administration ◽  
Average Value ◽  
Testing Method ◽  
Student Management ◽  
Usability Analysis ◽  
Speed Up ◽  
High Level ◽  
User Friendly

With the increasingly high level of exchange of information at this time, the demand for a system capable of managing all of that information is getting higher, where one of these systems is the Udayana University Student Management Information System (SIMAK) which has a vital role in the academic administration of Udayana University, which of course requires an interface that is easy to use so that it can speed up the process of academic administration, where it is one of the things that is often taken into consideration when designing an interface that is easy to use or user-friendly, to find out whether an interface from a user-friendly system can be done by testing the usability aspects of the system. Usability is one of the important aspects that must be fulfilled for a system where to find out whether the Usability aspect of a system is fulfilled, it can be tested using the Usability Testing method with questionnaire media, this study aims to examine the Usability aspects of the SIMAK system at Udayana University using the Usability method Testing with questionnaire media, where the results of this study indicate that the SIMAK system as a whole has met the Usability component with an average value of 3, which means that the SIMAK system of Udayana University already has a good Usability aspect value.

BOUNDED COCYCLES ON FINITE VON NEUMANN ALGEBRAS

2001 ◽  
Vol 12 (06) ◽  
pp. 743-750 ◽  
Author(s):  
TERESA BATES ◽  
THIERRY GIORDANO
Keyword(s):  
Discrete Group ◽  
Von Neumann Algebra ◽  
Von Neumann Algebras ◽  
Von Neumann ◽  
Countable Discrete Group ◽  
Finite Von Neumann Algebra ◽  
Finite Von Neumann Algebras ◽  
Uniformly Bounded

In this note we prove that if G is a countable discrete group, then every uniformly bounded cocycle from a standard Borel G-space into a finite Von Neumann algebra is cohomologous to a unitary cocycle. This generalizes results of both F. H. Vasilescu and L. Zsidó and R. J. Zimmer.

Time Optimal Trajectories for a Mobile Robot With Acceleration and Speed Limits in the Presence of an Obstacle

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
J. Z. Ben-Asher ◽  
E. D. Rimon ◽  
M. Wetzler ◽  
J. Diepolder
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Mobile Robot ◽  
Control Problem ◽  
Point Mass ◽  
Optimal Trajectories ◽  
Speed Limits ◽  
Optimal Paths ◽  
Time Optimal ◽  
Turn Rate

Abstract This paper studies the time optimal paths of a mobile robot navigating in a planar environment containing an obstacle. The paper considers a point-mass robot that moves with bounded acceleration and limited turn-rate controls in the presence of an obstacle. The optimal control problem yields 12 path primitives that form the time optimal paths of the point-mass robot. The problem is then extended to a disc-robot that moves in the presence of an obstacle with turn in-place capability. The optimality conditions yield 12 modified path primitives that form the time optimal paths of the disc-robot. All path primitives are analytically characterized and examples demonstrate how they form time optimal trajectories in the presence of several obstacle types.

Function space topologies defined by sectional integrals and applications to an extremal problem

1980 ◽  
Vol 87 (1) ◽  
pp. 81-96 ◽  
Author(s):  
K. J. Falconer
Keyword(s):  
Extremal Problem ◽  
Final Section ◽  
Convex Set ◽  
Compact Convex ◽  
Unit Vector ◽  
Extremal Values ◽  
Almost All ◽  
Function Space Topologies ◽  
Dimensional Lebesgue Measure ◽  
Uniformly Bounded

Let H(t, θ) be the hyperplane in Rn (n ≥ 2) which is perpendicular to the unit vector θ, and distant t from the origin; that is H(t, θ) = {x ε Rn: x.θ = t}. (Note that H(t, θ) and H(−t, − θ) are the same hyperplane.) If f(x) εℒ1(Rn), we will denote the integral of f with respect to (n − 1)-dimensional Lebesgue measure over H(t, θ) by F(t, θ), termed the projection or sectional integral of f over H(t,θ). By Fubini's theorem, F(t, θ) exists for almost all t for any θ. Throughout this paper we will assume that f(x) has support in X, a compact convex subset of Rn. In Section 2 we examine some of the topologies that may be defined on functions on X in terms of the F(t, θ), and in the remainder of the paper we examine the extremal problem suggested by Croft (4), that of maximizing the integral of f over the set X with the constraint that the F(t, θ) are uniformly bounded above. We examine in particular how the extremal values depend on the convex set X. In the final section the extremal problem is related to a generalization of Bang's plank theorem and the theory of capacities, and several conjectures are proposed.

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