Quantum optics near metal-dielectric interface: effects of quantum emitters

Abstract

The study of light-matter interactions is the most exciting and powerful technique for expanding our understanding of atomic and light physics. The past many years have further motivated this as applications for coherent control of matter were envisioned. These include applications as single-photon sources, efficient photon collection, single-photon transistor, and optical coupling of quantum bits over long distances for quantum communications. However, generating and controlling strong coherence can be difficult between otherwise weakly interacting quantum emitters (QEs) and light. Moreover, light and single emitters have vast size differences; hence, their light-matter interaction is weak. Nowadays, a wide range of solutions, including cavities, photonic bandgap structures, and optical lattices, have been improved and studied, but none has achieved superiority. However, the use of cavities and other methods limits the bandwidth and size of the devices. There has been another proposal to exploit the light-emitter interaction in the vicinity of plasmonic structures to develop future quantum technology. Plasmonic modes can be squeezed into regions significantly smaller than the diffraction limit, providing strong interaction between light and emitters. Surface plasmon Polaritons (SPPs), which are hybrid modes of light and electronic oscillations that propagate on the metal-dielectric interface, have been helpful in coupling to QEs such as single atoms or ions, quantum dots (QDs), color centers in diamonds, and fluorescent molecules. Earlier studies have already achieved the strong coupling between SPPs and various emitter types: J-aggregates, dye molecules, and quantum dots. QEs near metallic structures interact strongly with the SPP modes, modifying the radiation rates and the radiation profile. In addition, providing enhanced interaction between the emitters and light, SPPs due to highly confined fields offers new possibilities for the quantum control of light, enabling devices such as efficient single-photon sources, transistors, and ultra-compact circuitry at the nanoscale. This thesis aims to further explore the interaction between QEs and SPP modes present on metal-dielectric interface. We demonstrate that by employing two-level QEs near a metal-dielectric interface, one can prepare photons emitted from the QEs in path-entangled state. These photons display coalescence when detected by two detectors. In addition, the photons exhibits non-classical behaviour. We emphasize that in our model, long-range coupling between distant QEs is achievable by their common coupling to the SPPs. Our suggested architecture thereby opens up the possibility of on-chip quantum communication between several QEs. We propose that these photons can be further used for long-distance communication using free space or optical fiber. We also describe that our model can be implemented through already available technologies. Furthermore, such a system could also be used as an element in a distributed quantum network. Next, we present a method for enhancing the transmission of the SPP field using multiple interacting two-level QEs in a plasmonic environment. This is accomplished by arranging an array of two-level QEs along a plasmonic waveguide that interacts through guided SPP and non-waveguide photon modes. Our system depends on the quantum interference effect; it may be regarded as a plasmonic analog of electromagnetic induced transparency (EIT), usually associated with driven atomic systems. The fabrication of our proposed architecture is highly feasible, as several studies have indicated. Furthermore, similar to the Ising spin chain, our model with many interacting QEs may be employed for broadband transmission of the SPP field. In addition to transmission management, our work also paves the way for plasmonic devices such as slow light devices, and by using suitable waveguides tailored to the appropriate frequency, one can exploit different transmissions. Finally, we discuss nonlinear optical interactions that can be significantly enhanced at the nanoscale level using metallic structures. We describe non-linear surface plasmon polaritons, known as plasmon solitons confined to an interface between a nonlinear dielectric and a metal. Then, we express our current work and future ideas in the field of Non-linear plasmonics.