CQC2T SEMINAR (UNSW Sydney): Single-electron spin qubits in isotopically-enriched silicon at low magnetic field

August 8, 2019 @ 3:00 pm - 4:00 pm

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SPEAKER –  Dr Tuomo Tanttu, UNSW Sydney:


Many single-electron spin qubits employ magnetic fields at the order of 1 Tesla or above to enable quantum state readout via spin-dependent-tunnelling to an electron reservoir. This requires demanding microwave engineering for coherent spin resonance control and significant on-chip real estate, both of which limit the prospects for large scale multi-qubit systems. Alternatively, single-triplet (ST) readout enables high-fidelity spin-state measurement in much lower magnetic field [1]. Here, we enable low-field characterization of metal-oxide-silicon (MOS) quantum dot qubits by combining coherent single-spin control with high-fidelity, single-shot, Pauli-spin-blockade-based S-T readout. We discover that the qubits decohere faster at low magnetic fields with TRabi2 = 18.6 us and T = 1.4 us at 150 mT [2]. Their coherence is limited by spin flips of residual 29Si nuclei in the isotopically enriched 28Si host material, which occur more frequently at lower fields. Our finding indicates new trade-offs on frequency-stabilizing spin-qubits and highlights the importance of isotopic enrichment of device substrates for the realization of a scalable silicon-based quantum processor.

[1] M. Fogarty et al., Nature Commun. 9 (2018).

[2] R. Zhao et al., arXiv:1812.08347 (2018).


August 8, 2019
3:00 pm - 4:00 pm
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Old Main Building, UNSW
Room G59, Old Main Building, UNSW Kensington Campus NSW Australia


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