Misc,

Robust two-qubit gates in a linear ion crystal using a frequency-modulated driving force

, , , , , and .
(2017)cite arxiv:1708.08039.

Abstract

In an ion trap quantum computer, collective motional modes are used to entangle two or more qubits in order to execute multi-qubit logical gates. Any residual entanglement between the internal and motional states of the ions will result in decoherence errors, especially when there are many spectator ions in the crystal. We propose using a frequency-modulated (FM) driving force to minimize such errors and implement it experimentally. In simulation, we obtained an optimized FM gate that can suppress decoherence to less than $10^-4$ and is robust against a frequency drift of more than $\pm$1 kHz. The two-qubit gate was tested in a five-qubit trapped ion crystal, with $98.3(4)\%$ fidelity for a Mølmer-Sørensen entangling gate and $98.6(7)\%$ for a controlled-not (CNOT) gate. We also show an optimized FM two-qubit gate for 17 ions, proving the scalability of our method.

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