title: No-go theorem for ground state cooling given initial system-thermal bath factorization.
abstract: Ground-state cooling and pure state preparation of a small object that is embedded in a thermal environment is an important challenge and a highly desirable quantum technology. This paper proves, with two different methods, that a fundamental constraint on the cooling dynamic implies that it is impossible to cool, via a unitary system-bath quantum evolution, a system that is embedded in a thermal environment down to its ground state, if the initial state is a factorized product of system and bath states. The latter is a crucial but artificial assumption included in numerous tools that treat system-bath dynamics, such as master equation approaches and Kraus operator based methods. Adopting these approaches to address ground state and even approximate ground state cooling dynamics should therefore be done with caution, considering the fundamental theorem exposed in this work.
authors: Ikerbasque-Basque Foundation for Science and Department of Theoretical Physics and History of Science, The Basque Country University (EHU/UPV), PO Box 644, 48080 Bilbao, Spain. lianaowu@gmail.com
authors: Lian-Ao
authors: LA
authors: Wu
authors: Dvira
authors: D
authors: Segal
authors: Paul
authors: P
authors: Brumer
references: Phys Rev Lett. 2007 Aug 31;99(9):093901
references: 17931005
references: Phys Rev Lett. 2003 Jul 4;91(1):017402
references: 12906573
references: Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Oct;84(4 Pt 1):041109
references: 22181089
references: Phys Rev Lett. 2002 Jan 7;88(1):017901
references: 11800986
references: Nature. 2010 Jan 7;463(7277):72-5
references: 20010604
references: Phys Rev Lett. 2004 Feb 20;92(7):075507
references: 14995872
references: Phys Rev Lett. 1989 Jan 23;62(4):403-406
references: 10040224
references: Phys Rev A. 1992 Oct 1;46(7):4051-4054
references: 9908601
references: Nature. 2011 Oct 05;478(7367):89-92
references: 21979049
references: Nature. 2011 Jun 29;474(7353):589-97
references: 21720362
references: Nature. 2004 Dec 23;432(7020):1002-5
references: 15616555