Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits

• URL: http://arxiv.org/abs/2201.01583v2
• Date: Sat, 6 Aug 2022 14:50:20 GMT
• Title: Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits
• Authors: Guo Xuan Chan, Xin Wang
• Abstract summary: Search of a sweet spot, locus in qubit parameters where quantum control is first-order insensitive to noises, is key to achieve high-fidelity quantum gates. Efforts to search for such a sweet spot in conventional double-quantum-dot singlet-triplet qubits where each dot hosts one electron ("two-electron singlet-triplet qubit"), especially for two-qubit operations, have been unsuccessful. We consider singlet-triplet qubits allowing each dot to host more than one electron, with a total of four electrons in the double quantum dots ("four-electron singlet
• Score: 7.33811357166334
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: The search of a sweet spot, locus in qubit parameters where quantum control is first-order insensitive to noises, is key to achieve high-fidelity quantum gates. Efforts to search for such a sweet spot in conventional double-quantum-dot singlet-triplet qubits where each dot hosts one electron ("two-electron singlet-triplet qubit"), especially for two-qubit operations, have been unsuccessful. Here we consider singlet-triplet qubits allowing each dot to host more than one electron, with a total of four electrons in the double quantum dots ("four-electron singlet-triplet qubit"). We theoretically demonstrate, using configuration-interaction calculations, that sweet spots appear in this coupled qubit system. We further demonstrate that, under realistic charge noise and hyperfine noise, two-qubit operation at the proposed sweet spot could offer gate fidelities ($\sim99\%$) that are higher than conventional two-electron singlet-triplet qubit system ($\sim90\%$). Our results should facilitate realization of high-fidelity two-qubit gates in singlet-triplet qubit systems.

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