Masters Degrees (Physics)

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Browsing Masters Degrees (Physics) by Subject "Atom interferometry"

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    Quantum optical modelling and experiments investigating the population evolution in atomic zinc and ytterbium-171 ions
    (Stellenbosch : Stellenbosch University, 2022-04) Bester, Siann; Steenkamp, Christine M.; Neethling, Pieter H.; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT: This project sets out to derive, adapt and apply the four state optical Bloch equations to two very different experimental scenarios which are studied in our research group. These include modelling the first transition i n t he resonance ionization o f z inc between t he1S0 state and the 3P1 states. This transition is an electric dipole allowed but spin forbidden transition which is pumped by a pulsed laser. The second application is to model the qubit transition in the hyperfine levels o f t rapped y tterbium-171 ions. T his transition occurs in the 2S1/2 term, between the F = 0 ground state and the F = 1 excited states and is thus a magnetic dipole allowed transition which is driven by microwave radiation. This model was successfully derived and used to simulate various experiments where the following parameters within the model were varied: the spontaneous decay rate, the Rabi frequency, the laser’s detuning, the collisional rate and the external magnetic field. The model was used to identify when, in the case of the resonance ionization of zinc, it was acceptable to use the classical rate equations to model the transition. With the specific broad bandwidth pulsed laser which drives the transitions, it was found that the optical Bloch equations reduce to the rate equations due to the light being incoherent at the atoms. This is modelled by fast decay of the coherences between states. However, if a narrow bandwidth laser was used, then the four state optical Bloch model with averaging over the pulse’s spatial profile a nd t he p ulse t op ulse v ariationo f t he R abi frequency would be necessary to model the transition. The model was also used to accurately predict Rabi oscillations in trapped ytterbium- 171 ions and the model was fitted t o e xperimental d ata f rom a n m easurement o f Rabi oscillations. It was found that the four state model fitted the data better than the two state model even under conditions when only one of the excited states are pumped significantly. It was shown that the decay that was seen in the data was due to both losing ions from the trap as well as decoherence due to collisions within the system.