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Title: Two-qubit sweet spots for capacitively coupled exchange-only spin qubits
Authors: Feng, MengKe
Zaw, Lin Htoo
Koh, Teck Seng
Issue Date: 16-Jul-2021
Publisher: Nature Research
Citation: Feng, MengKe, Zaw, Lin Htoo, Koh, Teck Seng (2021-07-16). Two-qubit sweet spots for capacitively coupled exchange-only spin qubits. npj Quantum Information 7 (1) : 112. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: The implementation of high fidelity two-qubit gates is a bottleneck in the progress toward universal quantum computation in semiconductor quantum dot qubits. We study capacitive coupling between two triple quantum dot spin qubits encoded in the S = 1/2, Sz = ?1/2 decoherence-free subspace—the exchange-only (EO) spin qubits. We report exact gate sequences for CPHASE and CNOT gates, and demonstrate theoretically, the existence of multiple two-qubit sweet spots (2QSS) in the parameter space of capacitively coupled EO qubits. Gate operations have the advantage of being all-electrical, but charge noise that couple to electrical parameters of the qubits cause decoherence. Assuming noise with a 1/f spectrum, two-qubit gate fidelities and times are calculated, which provide useful information on the noise threshold necessary for fault-tolerance. We study two-qubit gates at single and multiple parameter 2QSS. In particular, for two existing EO implementations—the resonant exchange (RX) and the always-on exchange-only (AEON) qubits—we compare two-qubit gate fidelities and times at positions in parameter space where the 2QSS are simultaneously single-qubit sweet spots (1QSS) for the RX and AEON. These results provide a potential route to the realization of high fidelity quantum computation. © 2021, The Author(s).
Source Title: npj Quantum Information
ISSN: 2056-6387
DOI: 10.1038/s41534-021-00449-4
Rights: Attribution 4.0 International
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