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Entropy for Quantum Information Science

Project description

Laying a strong mathematical basis for quantum entropy

In the quantum realm, entropy is fundamental to quantifying the amount of information and correlations that are present in quantum systems. Unlike for systems described by classical mechanics, the mathematical knowledge of entropy for quantum systems is much more limited. The EU-funded QEntropy project aims to increase understanding of the mathematics of quantum entropy. In particular, the project will develop novel mathematical methods in matrix analysis and optimisation theory that will build the basis for a computational framework of approximation algorithms. The new framework is expected to solve a plethora of fundamental problems in quantum information science.


Entropy for quantum systems is the fundamental, interdisciplinary concept to quantify the advantage of quantum technologies for processing of information. It is well-established that the quantum advantage originates from the strong correlations found in the entanglement spectrum of multipartite quantum states, as exactly characterised by the information-theoretic tool quantum entropy. Contrary to the case of classical systems, however, our knowledge about the mathematics of quantum entropy is much more limited. Nonetheless, special entropy inequalities that are known to hold in the quantum case, such as the strong sub-additivity of quantum entropy, give crucial insights into the entanglement structure of multipartite quantum states. In this project, I will focus on understanding multipartite entropic constraints, which will lead to tight characterisations of the ultimate, physical limits of quantum information processing.

My recent mathematical works in quantum information led to operational extensions of the concept of strong sub-additivity from the seventies. Starting from that, I propose a research program that will lead to an understanding of quantum entropy that is on the same level as for the classical, commutative case. In the first part of my project, I will establish techniques in matrix analysis and optimisation theory to understand the interplay of arbitrarily many non-commuting operators. This mathematical framework will allow to prove novel quantum entropy inequalities that lead to refined approximations on the entanglement structure of multipartite quantum states. Second, I will employ the newly obtained entropic constraints to derive approximation algorithms for a plethora of fundamental problems in quantum information science. This includes schemes for achieving the physical limits of cryptography, resolving entropic additivity questions in information theory, and providing algorithms for the description of strongly interacting many body systems.

Host institution

Net EU contribution
€ 1 499 835,00
52062 Aachen

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Nordrhein-Westfalen Köln Städteregion Aachen
Activity type
Higher or Secondary Education Establishments
Total cost
€ 1 499 835,00

Beneficiaries (2)