We study energy-transport efficiency in light-harvesting planar and 3D complexes of two-level atomic quantum systems, embedded in a common thermal black-body radiation. Weshow that the collective non-local dissipation induced by the thermal bath plays a fundamental role in energy transport. It gives rise to a dramatic enhancement of the energy-transport efficiency, which may largely overcome 100%. This effect, which improves the understanding of transport phenomena in experimentally relevant complexes, suggests a particularly promising mechanism for quantum energy management.

We study an ensemble of two-level quantum systems (qubits) interacting with a common electromagnetic fieldin the proximity of a dielectric slab whose temperature is held different from that of some far surrounding walls.We show that the dissipative dynamics of the qubits driven by this stationary and out of thermal equilibriumfield allows the production of steady many-body entangled states, different from the case at thermal equilibriumwhere steady states are always nonentangled. By studying up to ten qubits, we point out the role of symmetry inthe entanglement production, which is exalted in the case of permutationally invariant configurations. In the caseof three qubits, we find a strong dependence of tripartite entanglement on the spatial disposition of the qubits,and in the case of six qubits we find several highly entangled bipartitions where entanglement can, remarkably,survive for large qubit-qubit distances up to 100 μm.

We propose a scheme for a quantum thermal machine made by atoms interacting with a single non equilibrium electromagnetic field. The field is produced by a simple configuration of macroscopic objects held at thermal equilibrium at different temperatures.We show that these machines can deliver all thermodynamic tasks (cooling, heating, and population inversion) by establishing quantum coherence with the body on which they act. Remarkably, this system allows these machines to reach efficiencies at maximum power very close to the Carnot limit, which is much more than in existing models. Our findings offer a paradigm for efficient quantum energy flux management, and can be relevant for both experimental and technological purposes.

Electromagnetic diffraction fromnanostructured objects: numerical challenges

We will discuss the behavior of an elementary quantum system (atom, quantum dot, …) interacting with an environment out of thermal equilibrium. We show how the internal atomic dynamics can be deeply affected by the non equilibrium configuration leading to unexpected phenomena like a spontaneous inversion of population, new cooling mechanisms obtained by heating the system, and the possibility to create and protect entanglement in a stationary and robust way [1,2,3].----------------References: [1] B. Bellomo, R. Messina, and M. Antezza, Europhys. Lett. 100, 20006 (2012); Phys. Rev. A 87, 012101 (2013).[2] B. Bellomo and M. Antezza, New Journal of Physics 15, 113052 (2013); Europhys. Lett. 104, 10006 (2013).[3] R. Messina and M. Antezza, Europhys. Lett. 95, 61002 (2011); Phys. Rev. A 84, 042102 (2011); Phys. Rev. A in press, arXiv:1402.2506 (2014).