48 research outputs found
A Survey on the Classical Limit of Quantum Dynamical Entropies
We analyze the behavior of quantum dynamical entropies production from
sequences of quantum approximants approaching their (chaotic) classical limit.
The model of the quantized hyperbolic automorphisms of the 2-torus is examined
in detail and a semi-classical analysis is performed on it using coherent
states, fulfilling an appropriate dynamical localization property.
Correspondence between quantum dynamical entropies and the Kolmogorov-Sinai
invariant is found only over time scales that are logarithmic in the
quantization parameter.Comment: LaTeX, 21 pages, Presented at the 3rd Workshop on Quantum Chaos and
Localization Phenomena, Warsaw, Poland, May 25-27, 200
Universality of spectra for interacting quantum chaotic systems
We analyze a model quantum dynamical system subjected to periodic interaction
with an environment, which can describe quantum measurements. Under the
condition of strong classical chaos and strong decoherence due to large
coupling with the measurement device, the spectra of the evolution operator
exhibit an universal behavior. A generic spectrum consists of a single
eigenvalue equal to unity, which corresponds to the invariant state of the
system, while all other eigenvalues are contained in a disk in the complex
plane. Its radius depends on the number of the Kraus measurement operators, and
determines the speed with which an arbitrary initial state converges to the
unique invariant state. These spectral properties are characteristic of an
ensemble of random quantum maps, which in turn can be described by an ensemble
of real random Ginibre matrices. This will be proven in the limit of large
dimension.Comment: 11 pages, 10 figure
QUANTUM DYNAMICAL ENTROPIES AND COMPLEXITY IN DYNAMICAL SYSTEMS
2002/2003We analyze the behavior of two quantum dynamical entropies in
connection with the classical limit. Using strongly chaotic
classical dynamical systems as models (Arnold Cat Maps and Sawtooth
Maps), we also propose a discretization procedure that resembles
quantization; even in this case, studies of quantum dynamical entropy
production are carried out and the connection with the continuous
limit is explored. In both case (quantization and discretization) the
entropy production converge to the Kolmogorov-Sinai invariant on
time-scales that are logarithmic in the quantization (discretization)
parameter.XVI Ciclo1969Versione digitalizzata della tesi di dottorato cartacea
Subnormalized states and trace-nonincreasing maps
We investigate the set of completely positive, trace-nonincreasing linear
maps acting on the set M_N of mixed quantum states of size N. Extremal point of
this set of maps are characterized and its volume with respect to the
Hilbert-Schmidt (Euclidean) measure is computed explicitly for an arbitrary N.
The spectra of partially reduced rescaled dynamical matrices associated with
trace-nonincreasing completely positive maps belong to the N-cube inscribed in
the set of subnormalized states of size N. As a by-product we derive the
measure in M_N induced by partial trace of mixed quantum states distributed
uniformly with respect to HS-measure in .Comment: LaTeX, 21 pages, 4 Encapsuled PostScript figures, 1 tabl
Distribution of G-concurrence of random pure states
Average entanglement of random pure states of an N x N composite system is
analyzed. We compute the average value of the determinant D of the reduced
state, which forms an entanglement monotone. Calculating higher moments of the
determinant we characterize the probability distribution P(D). Similar results
are obtained for the rescaled N-th root of the determinant, called
G-concurrence. We show that in the limit this quantity becomes
concentrated at a single point G=1/e. The position of the concentration point
changes if one consider an arbitrary N x K bipartite system, in the joint limit
, K/N fixed.Comment: RevTeX4, 11 pages, 4 Encapsuled PostScript figures - Introduced new
results, Section II and V have been significantly improved - To appear on PR
Random Quantum Operations
We define a natural ensemble of trace preserving, completely positive quantum
maps and present algorithms to generate them at random. Spectral properties of
the superoperator Phi associated with a given quantum map are investigated and
a quantum analogue of the Frobenius-Perron theorem is proved. We derive a
general formula for the density of eigenvalues of Phi and show the connection
with the Ginibre ensemble of real non-symmetric random matrices. Numerical
investigations of the spectral gap imply that a generic state of the system
iterated several times by a fixed generic map converges exponentially to an
invariant state
Continuous Limit of Discrete Sawtooth Maps and its Algebraic Framework
We study the presence of a logarithmic time scale in discrete approximations
of Sawtooth Maps on the 2--torus. The techniques used are suggested by quantum
mechanical similarities, and are based on a particular class of states on the
torus, that fulfill dynamical localization properties typical of quantum
Coherent States.Comment: LaTeX, 45 pages, 5 figures. Small changes in the content, references
added. To appear in J. Math. Phy
R&D Paths of Pixel Detectors for Vertex Tracking and Radiation Imaging
This report reviews current trends in the R&D of semiconductor pixellated
sensors for vertex tracking and radiation imaging. It identifies requirements
of future HEP experiments at colliders, needed technological breakthroughs and
highlights the relation to radiation detection and imaging applications in
other fields of science.Comment: 17 pages, 2 figures, submitted to the European Strategy Preparatory
Grou
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Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks
无线传感器网络,作为全球未来十大技术之一,集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术,可实时感知、采集、处理、传输网络分布区域内的各种信息数据,在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议,并针对大规模的无线传感器网络设计了一种树状路由协议,它根据节点地址信息来形成路由,从而简化了复杂繁冗的路由表查找和维护,节省了不必要的开销,提高了路由效率,实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR(AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位:工学硕士院系专业:信息科学与技术学院通信工程系_通信与信息系统学号:2332007115216