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A single-atom electron spin qubit in silicon

Abstract

A single atom is the prototypical quantum system, and a natural candidate for a quantum bit, or qubit—the elementary unit of a quantum computer. Atoms have been successfully used to store and process quantum information in electromagnetic traps1, as well as in diamond through the use of the nitrogen–vacancy-centre point defect2. Solid-state electrical devices possess great potential to scale up such demonstrations from few-qubit control to larger-scale quantum processors. Coherent control of spin qubits has been achieved in lithographically defined double quantum dots in both GaAs (refs 3–5) and Si (ref. 6). However, it is a formidable challenge to combine the electrical measurement capabilities of engineered nanostructures with the benefits inherent in atomic spin qubits. Here we demonstrate the coherent manipulation of an individual electron spin qubit bound to a phosphorus donor atom in natural silicon, measured electrically via single-shot read-out7,8,9. We use electron spin resonance to drive Rabi oscillations, and a Hahn echo pulse sequence reveals a spin coherence time exceeding 200 µs. This time should be even longer in isotopically enriched 28Si samples10,11. Combined with a device architecture12 that is compatible with modern integrated circuit technology, the electron spin of a single phosphorus atom in silicon should be an excellent platform on which to build a scalable quantum computer.

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Figure 1: Qubit device and pulsing scheme.
Figure 2: Rabi oscillations and power dependence of the Rabi frequency.
Figure 3: Coherence time and dynamical decoupling.
Figure 4: Qubit fidelity analysis.

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Acknowledgements

We thank R. P. Starrett, D. Barber, C. Y. Yang and R. Szymanski for technical assistance. We also thank A. Laucht for the Bloch sphere artwork and D. Reilly for comments on the manuscript. This research was funded by the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (project number CE11E0096) and the US Army Research Office (W911NF-08-1-0527). We acknowledge support from the Australian National Fabrication Facility.

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Contributions

K.Y.T. and W.H.L. fabricated the device; D.N.J. designed the phosphorus implantation experiments; J.J.P., K.Y.T., J.J.L.M. and J.P.D. performed the measurements; J.J.P., A.M., A.S.D. and J.J.L.M. designed the experiments and discussed the results; J.J.P. analysed the data; J.J.P. wrote the manuscript with input from all co-authors.

Corresponding authors

Correspondence to Jarryd J. Pla or Andrea Morello.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Text and Data 1-5, Supplementary Figures 1-5 and Supplementary References. (PDF 490 kb)

Supplementary Movie 1

This movie illustrates the procedure employed to initialise, control and measure the electron spin qubit. The qubit is first initalised in the spin-down state by subjecting it to the electric fields produced by a surface gate. Following this, microwaves are generated to coherently rotate the electron spin. Finally, spin-to-charge conversion is performed to read the state of the qubit. (MOV 12683 kb)

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Pla, J., Tan, K., Dehollain, J. et al. A single-atom electron spin qubit in silicon. Nature 489, 541–545 (2012). https://doi.org/10.1038/nature11449

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