Spatial Adiabatic Passage: light, sound and matter waves

Student thesis: Doctoral thesis

Abstract

The birth of Quantum Mechanics provided a theoretical framework that could explain some previously experimentally reported phenomena, such as the black body radiation, the photoelectric effect or the spectral lines of atomic gases, and also allowed for a better understanding of fundamental aspects related to the wave-particle duality and the interaction between radiation and matter. Quantum Mechanics has been also the origin of more specific disciplines such as Quantum Optics or Quantum Information science, which are partially devoted to a more applied research field that is known as Quantum Engineering. In this context, adiabatic passage processes consisting in the adiabatic following of an eigenstate of the system, which allows for a very robust and efficient control of the population transfer between two asymptotic states have been proposed. As many other processes in Quantum Mechanics, adiabatic passage processes are purely oscillatory and can be extended to other non-quantum physical systems, which also support oscillating quantities. In this thesis, spatial adiabatic passage processes are addressed in different oscillatory physical systems to control light, sound and matter waves propagation in systems of coupled waveguides, and the transfer of single cold atoms in harmonic potentials. Additionally, we make use of the robustness and high efficiency of the adiabatic passage to propose new devices and discuss new implementations in these various fields. To be specific, we experimentally demonstrate the spatial adiabatic passage of light in a system of three evanescent-coupled CMOS-compatible silicon oxide TIR waveguides, which consists in a complete transfer of light intensity between the outermost waveguides of the system. The advantage of using spatial adiabatic passage compared to standard directional couplers is that the light transfer is robust in front of technological fluctuations and does not depend on precise parameter values. Additionally, this is the first spatial adiabatic passage of light device fabricated in CMOS-compatible technology, which allows for massive and low cost integration. Furthermore, we also experimentally show that this system of coupled waveguides behaves as a simultaneously low- and high-pass spectral filter, with features that makes it an alternative to other integrated filters like interferenceñbased and absorbance-based filters. In addition, we address the spatial adiabatic passage of sound waves in systems of two coupled linear defects in sonic crystals. By calculating the band diagrams to analyze the available supermodes of the system and modifying the geometry of the linear defects along the propagation distance appropriately, we design devices working as a multifrequency adiabatic splitter, as a coupler and also as a phase difference analyser. Furthermore, we discuss a novel method to inject, extract and velocity filter neutral atoms in a ring trap via a spatial adiabatic passage process by using two extra waveguides. The proposal is based on the adiabatic following of a transversal eigenstate of the system. Semianalytical calculations are performed, which perfectly match with the results of the numerical integration of the Schrˆdinger equation. We also show that our proposal could be experimentally implemented for realistic state-of-the-art parameters of ultracold atoms in optical dipole potentials. Finally, we study the spatial adiabatic passage of a single cold atom in two-dimensional triple-well potentials, going beyond the well-understood effective one-dimensional systems and studying the possibilities arising from the additional degrees of freedom. On the one hand, a system of three coupled identical harmonic potentials with the traps lying in a triangular configuration is proposed for matter wave interferometry taking profit of a level crossing appearing in the energy spectrum. On the other hand, angular momentum is successfully generated in a similar configuration where the three harmonic traps have different trapping frequencies by simultaneously following two eigenstates of the system.
Date of Award13 Dec 2013
Original languageEnglish
Awarding Institution
  • Universitat Autònoma de Barcelona (UAB)
SupervisorJordi Mompart Penina (Director) & Veronica Ahufinger Breto (Director)

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