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날짜 2022-12-09 11:00 
일시 Dec. 9 (Fri), 11:00AM 
장소 E6-2 #1323 
연사 김도헌(서울대 물리천문학부 교수) 
세미나 영상은 아래 링크로 확인 바랍니다. (공개기간: 2022.12.15-2023.03.14, 3개월)
1. Date / Time 
    - Dec  9, 2022
    - 11:00 AM (KST)
2. Place: E6-2 #1323
3. Speaker
    - 김도헌 (서울대 물리천문학부 교수)
4. Talk Title
    - Two-electron quantum dot spin qubits in isotopically purified silicon
5. Abstract
Engineered spin-electric coupling is essential to enable fast manipulation of spins in semiconductor quantum dot (QD) nanostructures, especially in silicon. Although the placement of on-chip micromagnets has enabled single-spin qubits in silicon with gate fidelity to reach surface code-based error correction threshold, corresponding results using encoded spin qubits, for example, single-triplet qubits with high-quality quantum oscillations, have not been demonstrated. Instead, the spin-valley coupling has been recently used to enhance the electrical controllability of two-electron spin qubits in silicon at the expense of increased susceptibility to charge noise. Here, we demonstrate fast singlet-triplet qubit oscillation (~ 100MHz) of a quantum dot spin qubit in isotopically purified 28Si/SiGe substrate with an on-chip micromagnet in the regime where valley-splitting in each quantum dot exceeds 300 ueV. Combining rf-reflectometry-based single-shot readout and real time Hamiltonian estimation, we show that the oscillation quality factor of an encoded spin qubit over 1000 can be achieved. We further present the measurement of single-triplet qubit oscillation and variation of coherence time near the micro-magnet’s magnetization reversal, offering a route to in-situ tune magnetic field gradient and hence the Larmor frequency of the singlet-triplet qubit in silicon.
Attached: C.V
Inquiry: Prof. Se Kwon Kim( / Prof. Hee Jun Yang (
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