Thermal effects in the magnetic Casimir-Polder interaction

We investigate the magnetic dipole coupling between a metallic surface and an atom in a thermal state, ground state and excited hyperine state. This interaction results in a repulsive correction and - unlike the electrical dipole contribution - depends sensitively on the Ohmic dissipation in the material

Optical BCS conductivity at imaginary frequencies and dispersion energies of superconductors

We present an efficient expression for the analytic continuation to arbitrary complex frequencies of the complex optical and AC conductivity of a homogeneous superconductor with arbitrary mean free path. Knowledge of this quantity is fundamental in the calculation of thermodynamic potentials and dispersion energies involving type-I superconducting bodies. When considered for imaginary frequencies, our formula evaluates faster than previous schemes involving Kramers--Kronig transforms. A number of applications illustrates its efficiency: a simplified low-frequency expansion of the conductivity, the electromagnetic bulk self-energy due to longitudinal plasma oscillations, and the Casimir free energy of a superconducting cavity.Comment: 20 pages, 7 figures, calculation of Casimir energy adde

Temperature dependence of the magnetic Casimir-Polder interaction

We analyze the magnetic dipole contribution to atom-surface dispersion forces. Unlike its electrical counterpart, it involves small transition frequencies that are comparable to thermal energy scales. A significant temperature dependence is found near surfaces with a nonzero DC conductivity, leading to a strong suppression of the dispersion force at T > 0. We use thermal response theory for the surface material and discuss both normal metals and superconductors. The asymptotes of the free energy of interaction and of the entropy are calculated analytically over a large range of distances. Near a superconductor, the onset of dissipation at the phase transition strongly changes the interaction, including a discontinuous entropy. We discuss the similarities with the Casimir interaction beween two surfaces and suggest that precision measurements of the atom-surface interaction may shed new light upon open questions around the temperature dependence of dispersion forces between lossy media.Comment: 11 figure

Dynamical Casimir-Polder interaction between an atom and surface plasmons

We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze in particular how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relationof surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail.Comment: 12 pages, 8 figure

Squeezed Light from Entangled Nonidentical Emitters via Nanophotonic Environments

We propose a scheme in which broadband nanostructures allow for an enhanced two-photon nonlinearity that generates squeezed light from far-detuned quantum emitters via collective resonance fluorescence. To illustrate the proposal, we consider a pair of two-level emitters detuned by 400 line widths that are coupled by a plasmonic nanosphere. It is shown that the reduced fluctuations of the electromagnetic field arising from the interaction between the emitters provide a means to detect their entanglement. Due to the near-field enhancement in the proposed hybrid systems, these nonclassical effects can be encountered outside both the extremely close separations limiting the observation in free space and narrow frequency bands in high-Q cavities. Our approach permits overcoming the fundamental limitations to the generation of squeezed light from noninteracting single emitters and is more robust against phase decoherence induced by the environment

The squeezing spectrum of a quantum emitter coupled to an optical nanostructure

We analyze the spectral properties of the reduced quantum fluctuations arising from a single two-level emitter coupled to an optical nanostructure. A closed expression for the squeezing spectrum in this hybrid system is presented that includes the effect of additional phase decoherence. We consider a metallic nanoantenna to illustrate how the hybrid system can increase the bandwidth and overcome the limits to the generation of such spectral squeezing in terms of driving field intensity and the effect of pure dephasing

Polaritonic normal-mode splitting and light localization in a one-dimensional nanoguide

We theoretically investigate the interaction of light and a collection of emitters in a subwavelength one-dimensional medium (nanoguide), where enhanced emitter-photon coupling leads to efficient multiple scattering of photons. We show that the spectrum of the transmitted light undergoes normal-mode splitting even though no external cavity resonance is employed. By considering densities much higher than those encountered in cold atom experiments, we study the influence of the near-field dipole coupling and disorder on the resulting complex super-radiant and subradiant polaritonic states. In particular, we provide evidence for the longitudinal localization of light in a one-dimensional open system and provide a polaritonic phase diagram. Our results motivate a number of experiments, where new coherent superposition states of light and matter can be realized in the solid state

Polaritonic normal-mode splitting and light localization in a one-dimensional nanoguide

We theoretically investigate the interaction of light and a collection of emitters in a subwavelength one-dimensional medium (nanoguide), where enhanced emitter-photon coupling leads to efficient multiple scattering of photons. We show that the spectrum of the transmitted light undergoes normal-mode splitting even though no external cavity resonance is employed. By considering densities much higher than those encountered in cold atom experiments, we study the influence of the near-field dipole coupling and disorder on the resulting complex super-radiant and subradiant polaritonic states. In particular, we provide evidence for the longitudinal localization of light in a one-dimensional open system and provide a polaritonic phase diagram. Our results motivate a number of experiments, where new coherent superposition states of light and matter can be realized in the solid state

Small slot waveguide rings for on-chip quantum optical circuits

Nanophotonic interfaces between single emitters and light promise to enable new quantum optical technologies. Here, we use a combination of finite element simulations and analytic quantum theory to investigate the interaction of various quantum emitters with slot-waveguide rings. We predict that for rings with radii as small as 1.44 mu m, with a Q-factor of 27,900, near-unity emitter-waveguide coupling efficiencies and emission enhancements on the order of 1300 can be achieved. By tuning the ring geometry or introducing losses, we show that realistic emitter-ring systems can be made to be either weakly or strongly coupled, so that we can observe Rabi oscillations in the decay dynamics even for micron-sized rings. Moreover, we demonstrate that slot waveguide rings can be used to directionally couple emission, again with near-unity efficiency. Our results pave the way for integrated solid-state quantum circuits involving various emitters. (C) 2017 Optical Society of Americ