Coherent control of Rydberg atoms using sub-kHz linewidth excitation lasers

Student thesis: Doctoral Thesis

Abstract

This thesis presents the development of a new experimental apparatus for neutral atom quantum computing with Rydberg atoms. We describe the construction and characterisation of three continuous wave lasers stabilised simultaneously on a ultrahigh finesse Ultra-low-expansion (ULE) cavity, providing long-term stability and sub-kHz linewidth lasers with a tunable offset-lock frequency as required for high fidelity quantum operations. High-resolution spectroscopy on a cloud of cold Cs atoms was achieved using electromagnetically induced transparency (EIT), in order to calibrate absolute cavity mode frequencies with respect to Rydberg transitions and determine the cavity long-term drift of ~1 Hz/s.We have demonstrated trapping of single Cs atoms in optical tweezers and developed a high-resolution imaging system capable of sub-µm spatial resolution in the atom plane. Coherent control of atomic qubits has been achieved via fast rotations between long-lived hyperfine ground states as well as coherent Rydberg excitations towards the states 50S1/2, 69S1/2 and 81D5/2. The experiment allows us to control the atoms electric field environment and minimise stray electric fields with ~1 mV/cm sensitivity, in order to keep long ground-Rydberg coherence times.We have observed Rydberg blockade between two atoms separated by 6 µm for both states 69S1/2 and 81D5/2, showing an almost complete suppression of the doubly excited state probability. The creation of an entangled state is deduced from the √2 collective-enhancement of the Rabi oscillations with respect to the single atom case. Our ability to perform double-atom experiment offers the opportunity to implement a proof of a principle of a cNOT mesoscopic gate based on EIT, using the Rydberg state 81D5/2 for high-fidelity operations.
Date of Award9 Mar 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorJonathan Pritchard (Supervisor) & Erling Riis (Supervisor)

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