Fidelity optimisation in an atomic quantum computer

Research Team: Jack Saywell
Investigators: Timothy Freegarde

Component operations of a WALTZ composite pulse, designed to reduce the effect of detunings between the atomic qubit and the optical field performing the computational operation, depicted as trajectories on the surface of a Bloch sphere.

Quantum computers will use the coherence of individual quantum systems such as atoms for data storage, and tailored pulses of laser light may perform the computational operations. Although atoms are identical, systematic variations in laser intensity and environment mean that there are variations in the fidelity of these operations. Quantum error correction, specifically using 'composite pulse' techniques, allows the effects of these variations to be significantly reduced.

Composite pulse sequences were invented, and have mostly been developed, for NMR chemistry, and it is to such applications that existing sequences have been tailored. Atomic quantum computation has different aims, constraints and sensitivities, and therefore requires composite pulses of its own. This project will use and extend the computationally efficient toolboxes of Southampton's Spin Dynamics group to develop composite pulse sequences designed and optimized for the correction of errors in atomic quantum computers, first by addressing the 'beamsplitter' and 'mirror' functions of the underlying matterwave interferometry, then by treating the optimization of more complex operations in their entirety.

Computational Modelling Group

Fidelity optimisation in an atomic quantum computer

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