Improved high-fidelity transport of trapped-ion qubits through a multi-dimensional array

TL;DR

This paper demonstrates high-fidelity transport of trapped-ion qubits through a 2D array with an X-junction, significantly reducing motional excitation and exploring mode energy exchange for scalable quantum computing.

Contribution

It provides a detailed method for calculating transport potentials and achieving low motional excitation during ion transport in a 2D array.

Findings

Motional excitation reduced by a factor of 50 compared to previous work

Effective mitigation of excitation caused by transport mechanisms

Potential for cooling motional modes via energy exchange without lasers

Abstract

We have demonstrated transport of Be+ ions through a 2D Paul-trap array that incorporates an X-junction, while maintaining the ions near the motional ground-state of the confining potential well. We expand on the first report of the experiment [1], including a detailed discussion of how the transport potentials were calculated. Two main mechanisms that caused motional excitation during transport are explained, along with the methods used to mitigate such excitation. We reduced the motional excitation below the results in Ref. [1] by a factor of approximately 50. The effect of a mu-metal shield on qubit coherence is also reported. Finally, we examined a method for exchanging energy between multiple motional modes on the few-quanta level, which could be useful for cooling motional modes without directly accessing the modes with lasers. These results establish how trapped ions can be transported in a large-scale quantum processor with high fidelity.