Interaction in Quantum Communication

In some scenarios there are ways of conveying information with many fewer, even exponentially fewer, qubits than possible classically. Moreover, some of these methods have a very simple structure--they involve only few message exchanges between the communicating parties. It is therefore natural to ask whether every classical protocol may be transformed to a ``simpler'' quantum protocol--one that has similar efficiency, but uses fewer message exchanges. We show that for any constant k, there is a problem such that its k+1 message classical communication complexity is exponentially smaller than its k message quantum communication complexity. This, in particular, proves a round hierarchy theorem for quantum communication complexity, and implies, via a simple reduction, an Omega(N^{1/k}) lower bound for k message quantum protocols for Set Disjointness for constant k. Enroute, we prove information-theoretic lemmas, and define a related measure of correlation, the informational distance, that we believe may be of significance in other contexts as well.Comment: 35 pages. Uses IEEEtran.cls, IEEEbib.bst. Submitted to IEEE Transactions on Information Theory. Strengthens results in quant-ph/0005106, quant-ph/0004100 and an earlier version presented in STOC 200

Distillation of Greenberger-Horne-Zeilinger states by combinatorial methods

We prove a lower bound on the rate of Greenberger-Horne-Zeilinger states distillable from pure multipartite states by local operations and classical communication (LOCC). Our proof is based on a modification of a combinatorial argument used in the fast matrix multiplication algorithm of Coppersmith and Winograd. Previous use of methods from algebraic complexity in quantum information theory concerned transformations with stochastic local operations and classical operation (SLOCC), resulting in an asymptotically vanishing success probability. In contrast, our new protocol works with asymptotically vanishing error.Comment: 26 pages, 2 figures; v2: updated to match published versio

Generalizing the Sampling Property of the Q-function for Error Rate Analysis of Cooperative Communication in Fading Channels

This paper extends some approximation methods that are used to identify closed form Bit Error Rate (BER) expressions which are frequently utilized in investigation and comparison of performance for wireless communication systems in the literature. By using this group of approximation methods, some expectation integrals, which are complicated to analyze and have high computational complexity to evaluate through Monte Carlo simulations, are computed. For these integrals, by using the sampling property of the integrand functions of one or more arguments, reliable BER expressions revealing the diversity and coding gains are derived. Although the methods we present are valid for a larger class of integration problems, in this work we show the step by step derivation of the BER expressions for a canonical cooperative communication scenario in addition to a network coded system starting from basic building blocks. The derived expressions agree with the simulation results for a very wide range of signal-to-noise ratio (SNR) values.Comment: 5 pages, 5 figures, Submitted to IEEE International Symposium on Information Theory, ISIT 2013, Istanbul, Turke

Fundamental limits in Gaussian channels with feedback: confluence of communication, estimation, and control

The emerging study of integrating information theory and control systems theory has attracted tremendous attention, mainly motivated by the problems of control under communication constraints, feedback information theory, and networked systems. An often overlooked element is the estimation aspect; however, estimation cannot be studied isolatedly in those problems. Therefore, it is natural to investigate systems from the perspective of unifying communication, estimation, and control;This thesis is the first work to advocate such a perspective. To make Matters concrete, we focus on communication systems over Gaussian channels with feedback. For some of these channels, their fundamental limits for communication have been studied using information theoretic methods and control-oriented methods but remain open. In this thesis, we address the problems of characterizing and achieving the fundamental limits for these Gaussian channels with feedback by applying the unifying perspective;We establish a general equivalence among feedback communication, estimation, and feedback stabilization over the same Gaussian channels. As a consequence, we see that the information transmission (communication), information processing (estimation), and information utilization (control), seemingly different and usually separately treated, are in fact three sides of the same entity. We then reveal that the fundamental limitations in feedback communication, estimation, and control coincide: The achievable communication rates in the feedback communication problems can be alternatively given by the decay rates of the Cramer-Rao bounds (CRB) in the associated estimation problems or by the Bode sensitivity integrals in the associated control problems. Utilizing the general equivalence, we design optimal feedback communication schemes based on the celebrated Kalman filtering algorithm; these are the first deterministic, optimal communication schemes for these channels with feedback (except for the degenerated AWGN case). These schemes also extend the Schalkwijk-Kailath (SK) coding scheme and inherit its useful features, such as reduced coding complexity and improved performance. Hence, this thesis demonstrates that the new perspective plays a significant role in gaining new insights and new results in studying Gaussian feedback communication systems. We anticipate that the perspective could be extended to more general problems and helpful in building a theoretically and practically sound paradigm that unifies information, estimation, and control

Data Visualisation Does Political Things

In this paper I advance the theory of critical communication design by exploring the politics of data, information and knowledge visualisation in three bodies of work. Data reflects power relations, special interests and ideologies that determine which data is collected, what data is used and how it is used. In a review of Max Roser’s Our World in Data, I develop the concepts of digital positivism, datawash and darkdata. Looking at the Climaps by Emaps project, I describe how knowledge visualisation can support integrated learning on complex problems and nurture relational perception. Finally, I present my own Mapping Climate Communication project and explain how I used discourse mapping to develop the concept of discursive confusion and illustrate contradictions in this politicised area. Critical approaches to information visualisation reject reductive methods in favour of more nuanced ways of presenting information that acknowledge complexity and the political dimension on issues of controversy

SISTEM KOMUNIKASI PEMERINTAH DALAM KOMPLEKSITAS POKTAN FIKTIF PENGEMBANGAN KAMBING KALIGESING DI PURWOREJO

Government development system encouraged environment complexity like fictif farmers group. Those farmer groups existance when giving of Kaligesing goat from government. The aim of the research is to know how government communication system adapted in complexity of fictif farmer groups in Kaligesing goat farmings in Purworejo regency. Theory that had used is communication system in Niklas Luhmann perspective.Research methods that had used is conducted explorative case study.Population of the research in Purworejo regency which was the center of Kaligesing goat farming.The result of this research shown that government communication system was produced information about giving letter of decision from village heads for farmer groups which have activity in farmings. Government communication system was reproduced information about classification of farmer groups by subdistrict extension center and legacy of farmer groups. But those producing and reproducing of information wasn’t solved complexity effective because two factors. First, government communication system less interrelated with its sub systems. Second, government communication system less interrelated with others systems, especially political system.Keywords: government communication system, adaptation, complexity, fictif farmer groups, farmings of Kaligesing goat. Abstrak Sistem komunikasi Pemerintah menghadapi kompleksitas lingkungan berupa poktan fiktif. Poktan ini sering muncul ketika pemberian bantuan kambing Kaligesing oleh Pemerintah. Tujuan penelitian adalah untuk mengetahui bagaimana sistem komunikasi Pemerintah beradaptasi dalam kompleksitas poktan fiktif pengembangan kambing Kaligesing di kabupaten Purworejo. Teori yang digunakan adalah sistem komunikasi dalam perspektif Niklas Luhmann. Metode penelitian adalah studi kasus eksploratif. Populasi penelitian di kabupaten Purworejo yang menjadi sentra pengembangan kambing Kaligesing. Temuan penelitian menunjukkan bahwa sistem komunikasi Pemerintah sudah memroduksi informasi berupa pemberian Surat Keputusan Kepala Desa (SK Kades) untuk kelompok tani (poktan) yang aktif berkegiatan. Sistem juga mereproduksi informasi berupa pendataan poktan aktif oleh BPK dan kewajiban berbadan hukum. Namun produksi dan reproduksi ini tidak efektif menyelesaikan kompleksitas karena dua hal. Pertama, sistem kurang berinterrelasi dengan sub sistemnya. Kedua, sistem lemah dalam berinterrelasi dengan sistem diluar dirinya, terutama sistem politik. Katakunci:sistem komunikasi Pemerintah, adaptasi, kompleksitas, poktan fiktif, pengembangan kambing Kaligesin

Communication over Finite-Chain-Ring Matrix Channels

Though network coding is traditionally performed over finite fields, recent work on nested-lattice-based network coding suggests that, by allowing network coding over certain finite rings, more efficient physical-layer network coding schemes can be constructed. This paper considers the problem of communication over a finite-ring matrix channel $Y = AX + BE$, where $X$ is the channel input, $Y$ is the channel output, $E$ is random error, and $A$ and $B$ are random transfer matrices. Tight capacity results are obtained and simple polynomial-complexity capacity-achieving coding schemes are provided under the assumption that $A$ is uniform over all full-rank matrices and $BE$ is uniform over all rank-$t$ matrices, extending the work of Silva, Kschischang and K\"{o}tter (2010), who handled the case of finite fields. This extension is based on several new results, which may be of independent interest, that generalize concepts and methods from matrices over finite fields to matrices over finite chain rings.Comment: Submitted to IEEE Transactions on Information Theory, April 2013. Revised version submitted in Feb. 2014. Final version submitted in June 201

Data visualisation does political things

In this paper I advance the theory of critical communication design by exploring the politics of data, information and knowledge visualisation in three bodies of work. Data reflects power relations, special interests and ideologies that determine which data is collected, what data is used and how it is used. In a review of Max Roser’s Our World in Data, I develop the concepts of digital positivism, datawash and darkdata. Looking at the Climaps by Emaps project, I describe how knowledge visualisation can support integrated learning on complex problems and nurture relational perception. Finally, I present my own Mapping Climate Communication project and explain how I used discourse mapping to develop the concept of discursive confusion and illustrate contradictions in this politicised area. Critical approaches to information visualisation reject reductive methods in favour of more nuanced ways of presenting information that acknowledge complexity and the political dimension on issues of controversy