Coherent control of three-spin states in a triple quantum dot

Abstract

Spin qubits involving individual spins in single quantum dots or coupled spins in double quantum dots have emerged as potential building blocks for quantum information processing applications1,2,3,4. It has been suggested that triple quantum dots may provide additional tools and functionalities. These include encoding information either to obtain protection from decoherence or to permit all-electrical operation5, efficient spin busing across a quantum circuit6, and to enable quantum error correction using the three-spin Greenberger-Horn-Zeilinger quantum state. Towards these goals we demonstrate coherent manipulation of two interacting three-spin states. We employ the Landau–Zener–Stückelberg7,8 approach for creating and manipulating coherent superpositions of quantum states9. We confirm that we are able to maintain coherence when decreasing the exchange coupling of one spin with another while simultaneously increasing its coupling with the third. Such control of pairwise exchange is a requirement of most spin qubit architectures10, but has not been previously demonstrated.

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Figure 1: Device, three-spin states spectrum, and spin arch.
Figure 2: LZS oscillations from the two Δ′1/2−Q3/2 qubits for a wide (1,1,1) region.
Figure 3: Coherent three-spin state manipulation with a narrow (1,1,1) region
Figure 4: Magnetic field dependence of coherent three-spin state manipulation with a narrow (1,1,1) region.

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Acknowledgements

We thank D. G. Austing, W. Coish and E. Laird for discussions and O. Kodra for programming. A.S.S. and M.P-L. acknowledge funding from NSERC. G.G., A.K, M.P-L., and A.S.S. acknowledge funding from CIFAR. G.G. acknowledges funding from the NRC-CNRS collaboration.

Author information

Z.R.W. developed and grew the 2DEG heterostructure free of telegraphic noise; A.K. fabricated the triple quantum dot device capable of reaching the few-electron regime; P.Z., L.G. and S.A.S. designed and built the high-frequency lines up to 50 GHz at millikelvin temperatures; P.Z., L.G. and G.G. ran the cryogenic equipment; L.G., G.G., S.A.S. and M.P-L. developed the pulsing techniques; G.G., L.G. and S.A.S. performed the measurements; G.G., L.G. and G.C.A. analysed the data; G.C.A. performed theoretical simulations; G.G. and A.S.S. wrote the manuscript and Supplementary Information with input from all authors; G.G., L.G. and G.C.A made the figures; G.G., L.G., G.C.A., S.A.S., M.P-L. and A.S.S. participated in discussions concerning the experimental and theoretical results; and A.S.S. supervised the project.

Correspondence to A. S. Sachrajda.

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The authors declare no competing financial interests.

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Gaudreau, L., Granger, G., Kam, A. et al. Coherent control of three-spin states in a triple quantum dot. Nature Phys 8, 54–58 (2012). https://doi.org/10.1038/nphys2149

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