title: Entanglement enhances cooling in microscopic quantum refrigerators.
abstract: 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.
authors.affiliation: Département de Physique Théorique, Université de Genève, 1211 Genève, Switzerland and H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brunner
authors.affiliation: Department of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, United Kingdom and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain and Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
authors.forename: Marcus
authors.initials: M
authors.lastname: Huber
authors.affiliation: Department of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, United Kingdom.
authors.forename: Noah
authors.initials: N
authors.lastname: Linden
authors.affiliation: H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom.
authors.forename: Sandu
authors.initials: S
authors.lastname: Popescu
authors.affiliation: H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom.
authors.forename: Ralph
authors.initials: R
authors.lastname: Silva
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain.
authors.forename: Paul
authors.initials: P
authors.lastname: Skrzypczyk