Mauro Antezza

Casimir-Lifshitz force out of thermal equilibrium and heat transfer between arbitrary bodies

We study the Casimir-Lifshitz force and the radiative heat transfer occurring between two arbitrary bodies, each one held at a given temperature, surrounded by environmental radiation at a third temperature. The system, in stationary configuration out of thermal equilibrium, is characterized by a force and a heat transfer depending on the three temperatures, and explicitly expressed in terms of the scattering operators of each body. We find a closed-form analytic expression valid for bodies of any geometry and dielectric properties. As an example, the force between two parallel slabs of finite thickness is calculated, showing the importance of the environmental temperature as well as the occurrence of a repulsive interaction. An analytic expression is also provided for the force acting on an atom in front of a slab. Our predictions can be relevant for experimental and technological purposes.

Quantum systems in a stationary environment out of thermal equilibrium

We discuss how the thermalization of an elementary quantum system is modified when the system is placed in an environment out of thermal equilibrium. To this aim we provide a detailed investigation of the dynamics of an atomic system placed close to a body of arbitrary geometry and dielectric permittivity, whose temperature

Quantum metamaterials: a brave new world

{T}_{mathrm{M}}

Creation and protection of entanglement in systems out of thermal equilibrium

is different from that of the surrounding walls

Steady entanglement out of thermal equilibrium

{T}_{mathrm{W}}

Optomechanical Rydberg-atom excitation via dynamic Casimir-Polder coupling.

. A suitable master equation for the general case of an

Hyperbolic waveguide for long distance transport of near-field heat flux

N

Dynamics of an elementary quantum system in environments out of thermal equilibrium

-level atom is first derived and then specialized to the cases of a two- and three-level atom. Transition rates and steady states are explicitly expressed as a function of the scattering matrices of the body and become both qualitatively and quantitatively different from the case of radiation at thermal equilibrium. Out of equilibrium, the system steady state depends on the system-body distance, on the geometry of the body, and on the interplay of all such parameters with the body optical resonances. While a two-level atom tends toward a thermal state, this is not the case already in the presence of three atomic levels. This peculiar behavior can be exploited, for example, to invert the populations ordering and to provide an efficient cooling mechanism for the internal state of the quantum system. We finally provide numerical studies and asymptotic expressions when the body is a slab of finite thickness. Our predictions can be relevant for a wide class of experimental configurations out of thermal equilibrium involving different physical realizations of two- or three-level systems.

Quantum thermal machine acting on a many-body quantum system: Role of correlations in thermodynamic tasks.

Metamaterials are artificial, composite structures that present effective properties not encountered in natural materials. This broad definition can apply to many materials and types of properties. Consider, for instance, fiber-reinforced cement, a composite medium, made of cement and metallic fibers, with mechanical properties that neither of its components possesses alone. This is a (mechanical) metamaterial. The kinds of properties that we will be interested in here relate not to mechanics, but to electromagnetic waves. That is, we consider metamaterials whose electromagnetic properties, permittivity and permeability, can be tailored. (There is a similar concept with phonons, i.e., phononic metamaterials.) The field of composite media in electromagnetics is a rather old one. However, it has greatly expanded in recent years, in particular through the concepts of negative index, cloaking, superlenses, and even plasmonics. Various methods have been suggested to introduce quantum degrees of freedom. The use of metal in metamaterials and in plasmonics soon gave rise to the idea of inserting some gain inside these structures, which can be done by inserting quantum dots.1, 2 However, this approach uses quantum degrees of freedom not to modify the effective properties, but to compensate the losses. Somewhat differently, Plumridge and colleagues have shown the possibility of tailoring the anisotropic effective permittivity tensor of a layered medium doped by quantum wells.3 In recent work, Zagoskin and co-workers, who coined the term ‘quantum metamaterial,’ proposed using a set of charge qubits (an array of Josephson junctions).4 They showed that in such a system, a band gap can exist (depending on the microscopic quantum state of the qubits), resulting in a quantum photonic crystal. Another approach is to consider coupled-atom optical cavities.5 These metamaterials can be used to design a reconfigurable superlens possessing a negative index gradient for singlephoton imaging. Figure 1. Sketch of a quantum metamaterial made of an array of nanorods doped by quantum dots.

Thermally activated nonlocal amplification in quantum energy transport

We investigate the creation of entanglement between two quantum emitters interacting with a realistic common stationary electromagnetic field out of thermal equilibrium. In the case of two qubits we show that the absence of equilibrium allows the generation of steady entangled states, which is inaccessible at thermal equilibrium and is realized without any further external action on the two qubits. We first give a simple physical interpretation of the phenomenon in a specific case and then we report a detailed investigation on the dependence of the entanglement dynamics on the various physical parameters involved. Sub- and super-radiant effects are discussed, and qualitative differences in the dynamics concerning both creation and protection of entanglement according to the initial two-qubit state are pointed out.