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Title: A single ion inside a miniature cavity
Author: Steiner, Matthias
ISNI:       0000 0004 5358 6295
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2014
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This thesis describes the first experimentally achieved coupling of a single atomic ion to an optical fibre-cavity as well as the first photonic interaction between a single ion and a single semiconductor quantum dot. The newly developed apparatus stores a single Yb+ ion in a radio-frequency Paultrap. There the ion is overlapped in-situ with the field of a miniature Fabry-Perot cavity which is mounted on a 3D-translation stage. The key elements of the setup are the cavity mirrors which are microfabricated onto the front facets of optical fibres. The small size of these mirrors are ideal for integration with an electrode structure of similar dimensions. Moreover these cavities are intrinsically fibre coupled and thereby well suited for distributed networks based on photonic interaction. We focus in our studies of the cavity-ion interaction on the application of the cavity as a converter between atomic and photonic excitations. To this end, we investigate the probability of the ion to emit photons into the cavity mode and find that this rate exceeds the natural spontaneous emission rate of the transition. We confirm that the emitted light field consists of a stream of single photons by measuring the second order correlation function. Furthermore, when prepared in a single Zeeman state, the emission process correlates the polarisation of the photon with the spin state of the ion. Remarkably, swapping the roles of ion and light field does not affect the interaction strength, i.e. we observe strongly enhanced absorption by the ion when a faint probe beam is injected into the cavity mode. The novel cavity-ion geometry advances the prospects to reach the strong-coupling regime with single ions and the feasibility of a distributed ion-based quantum network. Finally we employ the cavity-enhanced absorption to demonstrate photonic coupling between an InAs/GaAs quantum dot and a Yb+ ion. The setups for both systems are spatially separated by 20 m and optically linked by a single mode fibre. Quantum dot photons are guided into the cavity and the absorption by the ion is investigated for various excitation parameters. Our results mark the first steps towards hybrid networks and set the stage for further studies of the interaction between this unequal couple.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral