Coherent singlet-triplet oscillations in a silicon-based double quantum dot

Abstract

Silicon is more than the dominant material in the conventional microelectronics industry: it also has potential as a host material for emerging quantum information technologies. Standard fabrication techniques already allow the isolation of single electron spins in silicon transistor-like devices. Although this is also possible in other materials, silicon-based systems have the advantage of interacting more weakly with nuclear spins. Reducing such interactions is important for the control of spin quantum bits because nuclear fluctuations limit quantum phase coherence, as seen in recent experiments in GaAs-based quantum dots1,2. Advances in reducing nuclear decoherence effects by means of complex control3,4,5 still result in coherence times much shorter than those seen in experiments on large ensembles of impurity-bound electrons in bulk silicon crystals6,7. Here we report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure and show that this system has a nuclei-induced dephasing time of 360 nanoseconds, which is an increase by nearly two orders of magnitude over similar measurements in GaAs-based quantum dots. The degree of phase coherence observed, combined with fast, gated electrical initialization, read-out and control, should motivate future development of silicon-based quantum information processors.

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Figure 1: Device design.
Figure 2: Spin blockade in the double quantum dot.
Figure 3: Rabi oscillation pulse sequence and data.
Figure 4: T 2 * pulse sequence and data.
Figure 5: Effective exchange energy versus detuning.

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Acknowledgements

We thank C. M. Marcus for discussions, J. R. Petta for assistance with measurement techniques and B. H. Fong for assistance with hyperfine calculations. Sponsored by United States Department of Defense. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the United States Department of Defense or the US Government. Approved for public release, distribution unlimited.

Author information

B.M.M., M.G.B., C.A.W., K.S.H. and A.T.H. contributed to device measurement and testing. B.H., P.W.D., I.A.-R., A.E.S. and M.S. contributed to material growth and device fabrication. B.M.M., T.D.L., A.A.K., R.S.R. and M.F.G. contributed to modelling and data analysis. B.M.M., T.D.L., A.A.K. and M.F.G prepared the manuscript.

Correspondence to B. M. Maune.

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Maune, B., Borselli, M., Huang, B. et al. Coherent singlet-triplet oscillations in a silicon-based double quantum dot. Nature 481, 344–347 (2012). https://doi.org/10.1038/nature10707

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