Quantum Entropy and Information

Subhash C. Kak

Jincheng Zhang

This paper proposes the Information Entropy Physical Quantization (IEPQ) framework, a novel approach to understanding the physical nature of information entropy within the context of quantum systems. The core claim of IEPQ is that information entropy can be physically quantifiable and exhibits a fundamental correspondence with quantum states. The proposed mechanism leverages quantum information theory, mapping information entropy to the description of quantum states. Utilizing quantum measurement and entanglement, IEPQ seeks to achieve the physical manipulation and transformation of information entropy. This work delves into the mathematical formalization of this framework, outlining key concepts and potential applications, primarily focusing on the theoretical development rather than experimental validation. The goal is to establish a bridge between information theory and quantum physics, offering a new perspective on the relationship between information and reality at the fundamental level. ---

Anil Kumar

This is intended to be an introductory book on information entropy. The concept of information theory is too broad to be captured by single definition. The term entropy is used in information theory to describe the amount of uncertainty. The information entropy is a fundamental quantity, related to thermodynamical entropy, which measures the extent of single particle density. The information and entropy both depend upon the choice of probability distribution. Quantum information science will lead to the creation of a quantum computer to solve problem that could not be solved by classical computer. The ideas from information theory have been applied to many problems of science and technology and in other different fields. Quantum Information entropy plays a crucial role in stronger formulation of uncertainty relation. The quantum information entropy of some important potentials is discussed which are widely used in different fields. The information entropy of these potentials is studied in position as well as momentum space and uncertainty relations are verified.

Masanori Ohya, Dėnes Petz

Progonov, Dmitro, Machusky, Eugene, Lucenko, Volodimir

Mark M. Wilde

In this chapter, we discuss several information measures that are important for quantifying the amount of information and correlations that are present in quantum systems. The first fundamental measure that we introduce is the von Neumann entropy (or simply quantum entropy ). It is the quantum generalization of the Shannon entropy, but it captures both classical and quantum uncertainty in a quantum state.1 The quantum entropy gives meaning to the notion of an information qubit . This notion is different from that of the physical qubit, which is the description of a quantum state of an electron or a photon. The information qubit is the fundamental quantum informational unit of measure, determining how much quantum information is present in a quantum system. The initial definitions here are analogous to the classical definitions of entropy, but we soon discover a radical departure from the intuitive classical notions from the previous chapter: the conditional quantum entropy can be negative for certain quantum states. In the classical world, this negativity simply does not occur, but it takes on a special meaning in quantum information theory. Pure quantum states that are entangled have stronger-than-classical correlations and are examples of states that have negative conditional entropy. The negative of the conditional quantum entropy is so important in quantum information theory that we even have a special name for it: the coherent information. We discover that the coherent information obeys a quantum data-processing inequality, placing it on a firm footing as a particular informational measure of quantum correlations. We then define several other quantum information measures, such as quantum mutual information, that bear similar definitions as in the classical world, but with Shannon entropies replaced with quantum entropies. This replacement may seem to make quantum entropy somewhat trivial on the surface, but a simple calculation reveals that a maximally entangled state on two qubits registers two bits of quantum mutual information (recall that the largest the mutual information can be in the classical world is one bit for the case of two maximally correlated bits). We then discuss several entropy inequalities that play an important role in quantum information processing: the monotonicity of quantum relative entropy, strong subadditivity, the quantum data-processing inequalities, and continuity of quantum entropy.