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We study the effects of a position-dependent artificial gauge field on an atomic Bose--Einstein condensate in quasi-one-dimensional and two-dimensional ring settings. The inhomogeneous artificial gauge field can induce global and local currents in the Bose--Einstein condensate via phase gradients along the ring and vortices, respectively. We observe two different regimes in the system depending on the radial size of the ring and strength of the gauge field. For weak artificial gauge fields, the angular momentum increases, as expected, in a quantized manner; however, for stronger values of the fields, the angular momentum exhibits a linear (non-quantized) behavior. We also characterize the angular momentum for non-cylindrically symmetric traps.

A plasmonic nanoparticle trap based on an array of nanoring structures with a 160 nm inner disk inside a 300 nm nanohole was demonstrated. Based on the extinction coefficient spectrum, 980 nm incident light was selected to trap 500 nm polystyrene particles. The transmitted intensity was collected for the power spectral density calculation to obtain the corner frequency. Compared to a conventional optical tweezers, approximately 20 times lower incident power is needed for this nanoring device to achieve the same trapping strength. Note from the author: With further experiments, we realized that at a higher incident power (as in the original proceeding, 1.45 mW) two-particle trapping events could happen and result in a higher value for the trap stiffness for the plasmonic tweezers. To eliminate two-particle trapping events, we have applied a lower incident power (0.6 mW) to guarantee single particle trapping and checked images of the trapped particle with a CCD camera. For a proper comparison to conventional optical tweezers, we updated the value of trap stiffness for our plasmonic tweezers for single, 0.5 µm polystyrene particle trapping at low incident power.

Recently developed techniques to operate, control and measure atomic systems on the micro- and nano-meter scale have created a tremendous interest in exploring how the presence of surfaces affects their quantum properties. This is partly driven by the interest to explore further fundamental physics, but on the practical side, atom-chips and other nano-scale devices are poised to become important in our daily lives. In this thesis, I present results obtained by studying how an evanescent field in the vicinity of a dielectric medium affects various quantum systems, namely one and two atom systems, as well as multi-component Bose-Einstein condensates.An evanescent field corresponds to an exponentially decaying mode above a surface, which emerges due to propagation of an electromagnetic wave inside a confined dielectric medium, such as a flat half-plane, an optical nano-fiber, or a prism. By bringing atoms close to the surface, the coupling to the evanescent field can strengthen the coupling between the atoms, resulting in multiple effects on their properties: frequency shifts can appear, emission rates can be modified and the dipole-dipole interaction between atoms can be enhanced.In the first project presented in this thesis, I show that the decay rate of two atoms near a flat dielectric surface is different compared to free space and can have oscillatory decaying behavior. This includes directional propagation of information between the atoms with a strength depending on the orientation of the two electric dipole moments, and on the relative location of the atoms to one another and to the surface of the dielectric medium. I also discuss the modification of the spontaneous emission rate when a multi-level atom is placed in the vicinity of an optical nano-fiber. Here the modifications do not only depend on the optical modes of the fiber, but also on the magnetic sub-levels and orientation of the electric dipole moment of the atom. A very interesting feature of atom-fiber systems is the possibility for spontaneous emission to be chiral. This effect again depends on the form of the available modes of the fiber and the orientation of electric dipole moment of the atom. In a second project I show that chiral emission also leads to a chiral recoil force on the atom and present a closed form expression for it. I then extend my studies to go beyond small systems and consider Bose-Einstein condensates of neutral atoms in the mean field limit. Exposing such systems to evanescent fields can be described as exposure to an artificial gauge field and be used to induce spatially inhomogeneous rotation into the condensate. In this part of the thesis, I show how localised rotation can affect the miscible to immiscible phase transition in two-component systems.