Spin Relaxation in Si/SiGe Quantum Dot Devices with Micromagnets*

Felix Borjans, David M. Zajac, Tom M. Hazard, Jason R. Petta
Department of Physics, Princeton University, Princeton, New Jersey, USA

Recent quantum control experiments in Si/SiGe quantum dots utilizing a micromagnet for electrically driven spin resonance have reported spin relaxation times (T1) ranging from 4 ms to more than 50 ms [1,2]. These T1 times are shorter than those obtained on samples without micromagnets, which suggests that the presence of the micromagnet is limiting T1 [3,4]. We measure T1 in a Si/SiGe device incorporating a micromagnet up to a magnetic field of 6 T. We find a saturation of T1 at low fields, evidence of a valley relaxation hotspot, and a soft B^3 field dependence above 2 T. These measurements indicate that the spin-orbit coupling induced by the micromagnet causes otherwise suppressed relaxation channels to dominate and limit qubit performance.

[1] Zajac et al., arXiv:1708.03530
[2] Watson et al., arXiv:1708.04214
[3] Hayes et al., arXiv:0908.0173
[4] Yang et al., Nature Comm. 4 2069 (2013)

*Research sponsored by ARO grant No. W911NF-15-1-0149, the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF4535, and NSF DMR-1409556. Devices were fabricated in the Princeton University Quantum Device Nanofabrication Laboratory.