Quantum thermal machine acting on a many-body quantum system: role of   correlations in thermodynamic tasks
  We study the functioning of a three-level thermal machine when acting on a many-qubit system, the entire system being placed in an electromagnetic field in a stationary out-of-thermal-equilibrium configuration. This realistic setup stands in between the two so-far explored cases of single-qubit and macroscopic object targets, providing information on the scaling with system size of purely quantum properties in thermodynamic contexts. We show that, thanks to the presence of robust correlations among the qubits induced by the field, thermodynamic tasks can be delivered by the machine both locally to each qubit and collectively to the many-qubit system: this allows a task to be delivered also on systems much bigger than the machine size. 
Pierre Doyeux, Bruno Leggio, Riccardo Messina, Mauro Antezza
quant-ph