Leakage mitigation for quantum error correction using a mixed qubit scheme

作     者：Brown, Natalie C. Brown, Kenneth R. 

作者机构：School of Physics Georgia Institute of Technology AtlantaGA United States Schools of Chemistry and Biochemistry and Computational Science and Engineering Georgia Institute of Technology AtlantaGA United States Departments of Electrical and Computer Engineering Chemistry and Physics Duke University DurhamNC United States 

出 版 物：《arXiv》 (arXiv)

年 卷 期：2019年

核心收录：

主　　题：Magnetic moments 

摘      要：Leakage errors take qubits out of the computational subspace and will accumulate if not addressed. A leaked qubit will reduce the effectiveness of quantum error correction protocols due to the cost of implementing leakage reduction circuits and the harm caused by interacting leaked states with qubit states. Ion trap qubits driven by Raman gates have a natural choice between qubits encoded in magnetically insensitive hyperfine states that can leak and qubits encoded in magnetically sensitive Zeeman states of the electron spin that cannot leak. In our previous work, we compared these two qubits in the context of the toric code with a depolarizing leakage error model and found that for magnetic field noise with a standard deviation less than 32 µG that the 174Yb+ Zeeman qubit outperforms the 171Yb+ hyperfine qubit. Here we examine a physically motivated leakage error model based on ions interacting via the Mølmer-Sørenson gate. We find that this greatly improves the performance of hyperfine qubits but the Zeeman qubits are more effective for magnetic field noise with a standard deviation less than 10 µG. At these low magnetic fields, we find that the best choice is a mixed qubit scheme where the hyperfine qubits are the ancilla and the leakage is handled without the need of an additional leakage reduction circuit. Copyright © 2019, The Authors. All rights reserved.