**Entanglement is a natural consequence of the superposition principle and a distinguishing feature in quantum mechanics. It is desirable to better understand and quantify the nature of entanglement within a quantum system and qubit systems appear to offer an ‘***excellent playground*’ for such investigations.

The main intention of this work, published recently in JPhysA is to show how measures of quantum entanglement (negativity and tangles) can be used to investigate the structure of entanglement in pure states of non-interacting qubits. The analysis focuses on constraints on the pattern of entanglement known to be satisfied by holographic sates, such as the saturation of Araki–Lieb inequality and the monogamy of mutual information.

This image, which shows a colour map of the monogamy of mutual information compared to the average ratio for the maximal bipartitions and mutipartite entanglement Ƭ4, has been taken from section 4 of the paper,* *in which the authors are investigating four qubits systems.

Mukund Rangamani and Massimiliano Rota work within the University or Durham’s Centre for Particle Theory, a collaboration of the theoretical particle physics groups from the Physics and Maths Departments. They research broadly within the field of theoretical particle physics ranging from phenomenology to string theory and cosmology.

This work is licensed under a Creative Commons Attribution 3.0 Unported License. Images: Mukund Rangamani and Massimiliano Rota 2015 *J. Phys. A: Math. Theor.* **48** 385301 copyright IOP Publishing Ltd 2015

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Categories: Journal of Physics A: Mathematical and Theoretical, JPhys+

Tags: Image of the week, Mathematical physics, Quantum Entanglement, Quantum information, Quantum mechanics