Dynamical Casimir effect and minimal temperature in quantum   thermodynamics
  We study the fundamental limitations of cooling to absolute zero for a qubit, interacting with a single mode of the electromagnetic field. Our results show that the dynamical Casimir effect, which is unavoidable in any finite-time thermodynamic cycle, forbids the attainability of the absolute zero of temperature, even in the limit of an infinite number of cycles. 
G. Benenti, G. Strini
quant-ph cond-mat.mes-hall cond-mat.stat-mech