Coherent information

About: Coherent information is a research topic. Over the lifetime, 1225 publications have been published within this topic receiving 46672 citations.

Identification Via Quantum Channels

Abstract: We review the development of the quantum version of Ahlswede and Dueck's theory of identification via channels. As is often the case in quantum probability, there is not just one but several quantizations: we know at least two different concepts of identification of classical information via quantum channels, and three different identification capacities for quantum information. In the present summary overview we concentrate on conceptual points and open problems, referring the reader to the small set of original articles for details.

Quantum Theory is an Information Theory

Abstract: In this paper we review the general framework of operational probabilistic theories (OPT), along with the six axioms from which quantum theory can be derived. We argue that the OPT framework along with a relaxed version of five of the axioms, define a general information theory. We close the paper with considerations about the role of the observer in an OPT, and the interpretation of the von Neumann postulate and the Schrodinger-cat paradox.

Coherent versus incoherent sequential quantum measurements

Abstract: We compare a trade-off between knowledge and decoherence for the incoherent and coherent partial sequential compatible measurements on single-qubit systems. The individual partial measurement nondestructively monitors basis states of the system by single-qubit meter. For the same decoherence caused by this unbiased measurement, the individual coherent measurement gives more knowledge than the incoherent one. For identical sequential coherent measurements, knowledge accumulated not additively increases more slowly than for the incoherent measurements. The overall knowledge can be accumulated using an adaptive measurement strategy on the meters if the single-qubit coherence of meters is kept. On the other hand, preservation of the mutual qubit coherence between the meters necessary for the collective measurement strategy is not required. A loss of single-qubit coherence degrades the coherent measurements back to the incoherent ones. Since the decoherence caused by the measurement process is a quadratic function of knowledge extracted by the individual measurement, Zeno-like behavior can be observed for repetitive weak compatible measurements. This unconditional universal effect does not depend on any dynamics of the qubit and it is a direct consequence of optimally controlled sequential evolution of quantum information.

Quantum Zero-Error Information Theory

Abstract: The first € price and the £ and $ price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. E.B. Guedes, F.M. de Assis, R.A.d.C. Medeiros Quantum Zero-Error Information Theory

On Dynamical Statistical Information Theory

Abstract: Static statistical information theory is extended to dynamic processes and a dynamical statistical information theory is built up, whose subject is the evolution law of the information entropy and information of dynamical systems. Starting from the state variable evolution equation nonlinear evolution equations of dynamic information entropy density and dynamic information density are derived, that describes respectively the evolution law of information entropy and information. These two equations show that the time rate of change of information entropy density originates together from the drift, diffusion and production in coodinate space and state variable space; and that the time rate of change of information density is caused by the drift, diffusion and dissipation in coodinate space and state variable space. Expressions of drift information flow and diffusion information flow, and concise formulas of information dissipation rate and information entropy production rate are given. It is proved that the rate of the information dissipation (or increase) is equal to the rate of information entropy production (or decrease) in the dynamic system, and that information diffusion and information dissipation happen at the same time. Dynamic mutual information reflecting the dynamic character in the transmission process is presented, which in the limiting case when the proportion of channel length to signal transmission rate approaches zero reduces itself to the present static mutual information. All the above results are derived in a unified fasion from evolution equations of information and information entropy without the addition of any extra assumptions. As exampless of application of the above theoretical formulation, information and information entropy as well as their time rates for three dynamic topics are investigated, viz.: the drift-diffusion transmission of Brownian motion, the kinetics of production of thermal defects, and molecular motors; and the dynamic mutual information of the Gaussian channel are presented.