SWAP Gate for Spin Qubits Based on Silicon Devices Integrated with a Micromagnet.

Ni, Ming; Ma, Rong-Long; Kong, Zhen-Zhen; Xue, Xiao; Zhu, Sheng-Kai; Wang, Chu; Li, Ao-Ran; Chu, Ning et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

In our toolbox of quantum gates for spin qubits, the SWAP-family gates based on Heisenberg exchange coupling are quite versatile: the SWAP gate can help solve the connectivity problem by realizing both short- and long-range spin state transfer, while the <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mrow><mi>S</mi><mi>W</mi><mi>A</mi><mi>P</mi></mrow></msqrt></math> gate is a basic two-qubit entangling gate. Here we demonstrate a SWAP gate in a double quantum dot in isotopically enriched silicon in the presence of a micromagnet. We achieve a two-orders-of-magnitude adjustable ratio between the exchange coupling <i>J</i> and the Zeeman energy difference Δ<i>E</i><sub><i>z</i></sub>, overcoming a major obstacle for a high-fidelity SWAP gate. We also calibrate the single-qubit local phases, evaluate the logical-basis fidelity of the SWAP gate, and further analyze the dominant error sources. These results pave the way for high-fidelity SWAP gates and processes based on them, such as quantum communication on chip and quantum simulation.