The work described in this thesis summarises some of the key milestones
achieved in the development of the UK’s first quantum computer based on
arrays of neutral atoms, delivered in partnership with M Squared Lasers Ltd.
These milestones include the commissioning of the 1064 nm optical dipole
trapping system for holographic array generation, assembly and testing of a
low phase noise microwave source used for global single qubit rotations and
the calibration of the Rydberg laser system locked to a narrow linewidth ultralow
expansion reference cavity.
Using 133Cs atoms, we demonstrate high-fidelity control over large scale arrays
with over 225 trap sites (> 100 qubits) by performing randomised benchmarking
(RB). The recorded average single qubit gate fidelity of 0.99993(2),
achieved using a global microwave driving field with composite pulses, is the
highest recorded fidelity on any platform of this size and comfortably meets
the thresholds of many error correction codes. To further advance the field
towards realising error correction, we also present the first practical application
of a non-destructive readout (NDRO) procedure based on a cycling
transition in alkali atoms. By increasing the trap depth and reducing the array
size to 49, the largest array size achieved with this technique to date, we
are able to demonstrate suppression of state preparation and measurement
errors during RB by a factor of 1.7 without affecting the average gate fidelity.
Finally, we present some early analogue simulation results of the quantum
one-dimensional Ising spin model on arrays of up to 9 atoms. Using this
simple, classically tractable problem, we characterise the performance of our
platform as an analogue optimisation device and identify key areas of improvement
as the experiment evolves into a state where more challenging
two-dimensional geometries can be simulated with a view of demonstrating
quantum advantage in optimisation problems with practical relevance.
| Date of Award | 24 Jan 2024 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | University of Strathclyde |
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| Supervisor | Jonathan Pritchard (Supervisor) & Erling Riis (Supervisor) |
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