Progress in the synthesis of colloidal quantum dots has recently provided access to entirely new forms of diluted magnetic semiconductors1, some of which may find use in quantum computation2,3,4,5,6. The usefulness of a spin qubit is defined by its Rabi frequency, which determines the operation time, and its coherence time, which sets the error correction window7. However, the spin dynamics of magnetic impurity ions in colloidal doped quantum dots remain entirely unexplored. Here, we use pulsed electron paramagnetic resonance spectroscopy to demonstrate long spin coherence times of ∼0.9 µs in colloidal ZnO quantum dots containing the paramagnetic dopant Mn2+, as well as Rabi oscillations with frequencies ranging between 2 and 20 MHz depending on microwave power. We also observe electron spin echo envelope modulations of the Mn2+ signal due to hyperfine coupling with protons outside the quantum dots, a situation unique to the colloidal form of quantum dots, and not observed to date.
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The authors acknowledge financial support from the US National Science Foundation (CHE 0628252-CRC to D.G.) and the University of Washington. EPR instrumentation support was provided by the Center for Ecogenetics and Environmental Health UW Center grant no. P30 ES07033 from the National Institute of Environmental Health Sciences (NIH). K.M. Whitaker and V.A. Vlaskin are thanked for valuable assistance with the synthesis of the QDs and TEM, respectively.
The authors declare no competing financial interests.
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Ochsenbein, S., Gamelin, D. Quantum oscillations in magnetically doped colloidal nanocrystals. Nature Nanotech 6, 112–115 (2011). https://doi.org/10.1038/nnano.2010.252
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