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Coherence properties of shallow donors in ZnO

Kai-Mei Fu, University of Washington
Thursday, February 1, 2018 - 12:30pm to 1:30pm
PAB C-520

​After a brief overview of the desired properties for defect-based quantum bits, I present recent measurements on the coherence properties of donor-bound electrons in ZnO.  Using all-optical spin control, we find a longitudinal relaxation time T1 exceeding 100 ms, an inhomogeneous dephasing time T2* of 17 nanoseconds, and a Hahn spin-echo time T2 of 50 microseconds. The magnitude of T2* is consistent with the inhomogeneity of the nuclear hyperfine field in natural ZnO.  Possible mechanisms limiting T2 include instantaneous diffusion and nuclear spin diffusion (spectral diffusion). These results are comparable to the phosphorous donor system in natural silicon, suggesting that with isotope and chemical purification long qubit coherence times can be obtained for donor spins in a direct band gap semiconductor.