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Title: Towards high fidelity entanglement with dressed state qubits
Author: Lake, Kimberley
ISNI:       0000 0004 5347 930X
Awarding Body: University of Sussex
Current Institution: University of Sussex
Date of Award: 2015
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This thesis describes the development of an entanglement experiment for ytterbium ions making use of a new entanglement method utilizing microwaves and a static magnetic field gradient. This thesis will begin by modelling the populations of the main levels in ytterbium using rate equations to find the optimum parameters required for the preparation and detection of qubit states. Coherent manipulation of these qubit states will be shown and coherence times of the states measured. Additionally a highly stable double resonance frequency locking setup for the ytterbium cooling lasers is built. This thesis will go on to give an overview of the main entanglement schemes and will give a justification as to why microwaves combined with a magnetic field gradient is the most suitable method. The magnetic field gradient creates an effective Lamb-Dicke parameter which allows microwave fields to couple to the motional states of magnetic field sensitive qubit states. The use of magnetic field sensitive states can however make the qubit highly susceptible to decoherence from magnetic field fluctuations. A method to decrease this decoherence by two orders of magnitude using a microwave dressed state qubit will be demonstrated and optimised and a new coherent manipulation method of the dressed state qubit will be presented which allows for arbitrary Bloch sphere rotations. The production of the highest recorded magnetic field gradient of 24Tm⁻¹ at the position of the trapped ion using in-vacuum permanent magnets is shown and used to provide individual addressing of ions. Static gradient microwave entanglement of a single ion's internal and motional states within the bare qubit states is then demonstrated (Schrodinger cat states). Furthermore, the first ever observation of motional coupling of the microwave dressed state qubit is shown and progress towards a two ion entanglement gate with microwave dressed state qubits is reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics