%0 Journal Article
%J Physical Review E
%D 2014
%T Entanglement enhances cooling in microscopic quantum refrigerators
%A Nicolas Brunner
%A Huber, Marcus
%A Noah Linden
%A Sandu Popescu
%A Ralph Silva
%A Paul Skrzypczyk
%X Small self-contained quantum thermal machines function without external source of work or control, but using only incoherent interactions with thermal baths. Here we investigate the role of entanglement in a small self-contained quantum refrigerator. We first show that entanglement is detrimental as far as efficiency is concerned---fridges operating at efficiencies close to the Carnot limit do not feature any entanglement. Moving away from the Carnot regime, we show that entanglement can enhance cooling and energy transport. Hence a truly quantum refrigerator can outperform a classical one. Furthermore, the amount of entanglement alone quantifies the enhancement in cooling.
%B Physical Review E
%V 89
%8 3/2014
%N 3
%! Phys. Rev. E
%R 10.1103/PhysRevE.89.032115
%0 Journal Article
%J Linear Algebra and its Applications
%D 2014
%T Inequalities for the ranks of multipartite quantum states
%A Josh Cadney
%A Huber, Marcus
%A Noah Linden
%A Winter, Andreas
%X We investigate relations between the ranks of marginals of multipartite quantum states. These are the Schmidt ranks across all possible bipartitions and constitute a natural quantification of multipartite entanglement dimensionality. We show that there exist inequalities constraining the possible distribution of ranks. This is analogous to the case of von Neumann entropy (\alpha-R\'enyi entropy for \alpha=1), where nontrivial inequalities constraining the distribution of entropies (such as e.g. strong subadditivity) are known. It was also recently discovered that all other \alpha-R\'enyi entropies for α∈(0,1)∪(1,∞) satisfy only one trivial linear inequality (non-negativity) and the distribution of entropies for α∈(0,1) is completely unconstrained beyond non-negativity. Our result resolves an important open question by showing that also the case of \alpha=0 (logarithm of the rank) is restricted by nontrivial linear relations and thus the cases of von Neumann entropy (i.e., \alpha=1) and 0-R\'enyi entropy are exceptionally interesting measures of entanglement in the multipartite setting.
%B Linear Algebra and its Applications
%V 452
%P 153 - 171
%8 07/2014
%! Linear Algebra and its Applications
%R 10.1016/j.laa.2014.03.035
%0 Conference Proceedings
%B Proc. 8th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2013)
%D 2013
%T The Quantum Entropy Cone of Stabiliser States
%A Noah Linden
%A Frantisek Matus
%A Mary Beth Ruskai
%A Winter, Andreas
%E Severini, Simone
%E Fernando Brandao
%B Proc. 8th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2013)
%S LIPICS
%I Leibniz International Proceedings in Informatics (LIPICS)
%C Guelph, ON
%V 22
%P 270 - 284
%8 06/2013
%R 10.4230/LIPIcs.TQC.2013.270