Experimental demonstration of high-fidelity entanglement via Rydberg blockade

The strong dipole interactions of Rydberg atoms are ideal candidates to facilitate interactions between neutral atoms to generate entanglement for quantum information processing. This offers the potential to scale to large atom arrays through well established techniques for neutral atoms, overcoming limitations of other architectures for quantum information processing. This thesis presents the design and development of an experiment for quantum information processing using Rydberg atoms, concluding with the deterministic preparation of two caesium atomic qubits in a maximumly entangled Bell state.The experiment presented achieves low error readout of two single atoms held in optical tweezers using new imaging technology as an alternative to what is typically used in the field, offering a cost effective solution whilst maintaining high shot to shot retention as is necessary for qubit operations. Qubit manipulations are demonstrated with fast two-photon rotations between the hyperfine ground states and the 69S1/2 Rydberg state. Due to the cold single atom temperatures achieved, T ≈ 10 μK, the ground-Rydberg dephasing times measured through Ramsey spectroscopy find coherence times around twice that of previously reported experiments, over an order of magnitude greater than the gate time.;Demonstration of Rydberg blockade between two atoms with a separation of 6 μm is shown with an almost compete suppression to the doubly excited state and observation of a √2-enhancement of coupling to an entangled symmetric |W〉 state. Finally the |W〉 state is mapped to the ground state qubit levels to create a maximally entangled Bell state achieving a loss-corrected fidelity of Ƒpairs = 0:81 ± 0:05. This result represents the highest corrected ground state neutral atom entanglement fidelity via Rydberg blockade and is equal to that achieved via Rydberg dressing . The limitation of this Bell state preparation is primarily due to laser phase noise as found in other experiments and is verified through the long coherence times measured in this thesis. Generation of entanglement in the magnetically insensitive hyperfine states of caesium allows long coherence times to be achieved with Ramsey spectroscopy used to measured transverse dephasing times of T*₂ = 10± 1 ms and T'2 = 150 ± 20 ms, offering an excellent platform for quantum computation.The strong dipole interactions of Rydberg atoms are ideal candidates to facilitate interactions between neutral atoms to generate entanglement for quantum information processing. This offers the potential to scale to large atom arrays through well established techniques for neutral atoms, overcoming limitations of other architectures for quantum information processing. This thesis presents the design and development of an experiment for quantum information processing using Rydberg atoms, concluding with the deterministic preparation of two caesium atomic qubits in a maximumly entangled Bell state.The experiment presented achieves low error readout of two single atoms held in optical tweezers using new imaging technology as an alternative to what is typically used in the field, offering a cost effective solution whilst maintaining high shot to shot retention as is necessary for qubit operations. Qubit manipulations are demonstrated with fast two-photon rotations between the hyperfine ground states and the 69S1/2 Rydberg state. Due to the cold single atom temperatures achieved, T ≈ 10 μK, the ground-Rydberg dephasing times measured through Ramsey spectroscopy find coherence times around twice that of previously reported experiments, over an order of magnitude greater than the gate time.;Demonstration of Rydberg blockade between two atoms with a separation of 6 μm is shown with an almost compete suppression to the doubly excited state and observation of a √2-enhancement of coupling to an entangled symmetric |W〉 state. Finally the |W〉 state is mapped to the ground state qubit levels to create a maximally entangled Bell state achieving a loss-corrected fidelity of Ƒpairs = 0:81 ± 0:05. This result represents the highest corrected ground state neutral atom entanglement fidelity via Rydberg blockade and is equal to that achieved via Rydberg dressing . The limitation of this Bell state preparation is primarily due to laser phase noise as found in other experiments and is verified through the long coherence times measured in this thesis. Generation of entanglement in the magnetically insensitive hyperfine states of caesium allows long coherence times to be achieved with Ramsey spectroscopy used to measured transverse dephasing times of T*₂ = 10± 1 ms and T'2 = 150 ± 20 ms, offering an excellent platform for quantum computation

Two-Atom Collisions and the Loading of Atoms in Microtraps

We review light assisted collisions in a high-density far-off resonant optical trap (FORT). By tuning the parameters of the light that induces the collisions, the effects of the collisions can be controlled. Trap loss can be suppressed even at high atomic densities, allowing us to count the atoms using fluorescence detection. When only two atoms are trapped, individual loss events reveal new information about the process, and the simplicity of the system allows for a numerical simulation of the dynamics. By optimizing the experimental parameters, we implement an efficient method to prepare single atoms in the FORT. Our methods can be extended to load quantum registers for quantum information processing