Single-shot read-out of an individual electron spin in a quantum dot


Spin is a fundamental property of all elementary particles. Classically it can be viewed as a tiny magnetic moment, but a measurement of an electron spin along the direction of an external magnetic field can have only two outcomes1: parallel or anti-parallel to the field. This discreteness reflects the quantum mechanical nature of spin. Ensembles of many spins have found diverse applications ranging from magnetic resonance imaging2 to magneto-electronic devices3, while individual spins are considered as carriers for quantum information. Read-out of single spin states has been achieved using optical techniques4, and is within reach of magnetic resonance force microscopy5. However, electrical read-out of single spins6,7,8,9,10,11,12,13 has so far remained elusive. Here we demonstrate electrical single-shot measurement of the state of an individual electron spin in a semiconductor quantum dot14. We use spin-to-charge conversion of a single electron confined in the dot, and detect the single-electron charge using a quantum point contact; the spin measurement visibility is 65%. Furthermore, we observe very long single-spin energy relaxation times (up to 0.85 ms at a magnetic field of 8 T), which are encouraging for the use of electron spins as carriers of quantum information.

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Figure 1: Spin-to-charge conversion in a quantum dot coupled to a quantum point contact.
Figure 2: Two-level pulse technique used to inject a single electron and measure its spin orientation.
Figure 3: Single-shot read-out of one electron spin.
Figure 4: Measurement fidelity.


  1. 1

    Sakurai, J. J. Modern Quantum Mechanics (Addison-Wesley, Reading, Massachusetts, 1994)

    Google Scholar 

  2. 2

    Wehrli, F. W. The origins and nature of nuclear magnetic resonance imaging. Phys. Today 6, 34–42 (1992)

    Article  Google Scholar 

  3. 3

    Wolf, S. A. et al. Spintronics: a spin-based electronics vision for the future. Science 294, 1488–1495 (2001)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Blatt, R. & Zoller, P. Quantum jumps. Eur. J. Phys. 9, 250–279 (1988)

    CAS  Article  Google Scholar 

  5. 5

    Rugar, D., Budakian, R., Mamin, H. J. & Chui, B. W. Single spin detection by magnetic resonance force microscopy. Nature 430, 329–332 (2004)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Loss, D. & DiVincenzo, D. P. Quantum computation with quantum dots. Phys. Rev. A 57, 120–126 (1998)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Kane, B. E. A silicon-based nuclear spin quantum computer. Nature 393, 133–137 (1998)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Vandersypen, L. M. K., et al. in Quantum Computing and Quantum Bits in Mesoscopic Systems (eds Legget, A. J., Ruggiero, B. & Silvestrini, P.) 201–209 (Kluwer Academic/Plenum, New York, 2003); 〈〉 (2002)

    Google Scholar 

  9. 9

    Xiao, M., Martin, I. & Jiang, H. W. Probing the spin state of a single electron trap by random telegraph signal. Phys. Rev. Lett. 91, 078301 (2003)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Friesen, M., Tahan, C., Joynt, R. & Eriksson, M. A. Spin readout and initialization in a semiconductor quantum dot. Phys. Rev. Lett. 92, 037901 (2004)

    ADS  Article  Google Scholar 

  11. 11

    Engel, H. et al. Measurement efficiency and n-shot read out of spin qubits. Phys. Rev. Lett. (in the press); preprint at 〈〉 (2003)

  12. 12

    Ionicioiu, R. & Popescu, A. E. Single spin measurement using spin-orbital entanglement. Preprint at 〈〉 (2003).

  13. 13

    Greentree, A. D., Hamilton, A. R., Hollenberg, L. C. L. & Clark, R. G. Electrical readout of a spin qubit without double occupancy. Preprint at 〈〉 (2004).

  14. 14

    Kouwenhoven, L. P., Austing, D. G. & Tarucha, S. Few-electron quantum dots. Rep. Prog. Phys. 64, 701–736 (2001)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Weis, J., Haug, R. J., von Klitzing, K. & Ploog, K. Lateral transport through a single quantum dot with a magnetic field parallel to the current. Surf. Sci. 305, 664–668 (1994)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Kouwenhoven, L. P. et al. Excitation spectra of circular, few-electron quantum dots. Science 278, 1788–1792 (1997)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Ciorga, M. et al. Readout of a single electron spin based quantum bit by current detection. Physica E 11, 35–40 (2001)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Fujisawa, T., Austing, D. G., Tokura, Y., Hirayama, Y. & Tarucha, S. Allowed and forbidden transitions in artificial hydrogen and helium atoms. Nature 419, 278–281 (2002)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Hanson, R. et al. Zeeman energy and spin relaxation in a one-electron quantum dot. Phys. Rev. Lett. 91, 196802 (2003)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Folk, J. A., Potok, R. M., Marcus, C. M. & Umansky, V. A gate-controlled bidirectional spin filter using quantum coherence. Science 299, 679–682 (2003)

    ADS  CAS  Article  Google Scholar 

  21. 21

    Lu, W., Ji, Z., Pfeiffer, L., West, K. W. & Rimberg, A. J. Real-time detection of electron tunnelling in a quantum dot. Nature 423, 422–425 (2003)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Fujisawa, T., Hayashi, T., Hirayama, Y., Cheong, H. D. & Jeong, Y. H. Electron counting of single-electron tunnelling current. Appl. Phys. Lett. 84, 2343–2345 (2004)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Elzerman, J. M. et al. Few-electron quantum dot circuit with integrated charge read out. Phys. Rev. B 67, 161308 (2003)

    ADS  Article  Google Scholar 

  24. 24

    Elzerman, J. M., Hanson, R., Willems van Beveren, L. H., Vandersypen, L. M. K. & Kouwenhoven, L. P. Excited-state spectroscopy on a nearly-closed quantum dot via charge detection. Appl. Phys. Lett. 84, 4617–4619 (2004)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Field, M. et al. Measurements of Coulomb blockade with a noninvasive voltage probe. Phys. Rev. Lett. 70, 1311–1314 (1993)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Hanson, R. et al. Semiconductor few-electron quantum dot operated as a bipolar spin filter. Preprint at 〈〉 (2003).

  27. 27

    Khaetskii, A. V. & Nazarov, Y. V. Spin-flip transitions between Zeeman sublevels in semiconductor quantum dots. Phys. Rev. B 64, 125316 (2001)

    ADS  Article  Google Scholar 

  28. 28

    Golovach, V. N., Khaetskii, A. & Loss, D. Phonon-induced decay of the electron spin in quantum dots. Preprint at 〈〉 (2003).

  29. 29

    Woods, L. M., Reinecke, T. L. & Lyanda-Geller, Y. Spin relaxation in quantum dots. Phys. Rev. B 66, 161318 (2002)

    ADS  Article  Google Scholar 

  30. 30

    Erlingsson, S. I. & Nazarov, Y. V. Hyperfine-mediated transitions between a Zeeman split doublet in GaAs quantum dots: The role of the internal field. Phys. Rev. B 66, 155327 (2002)

    ADS  Article  Google Scholar 

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We thank D. P. DiVincenzo, H. A. Engel, T. Fujisawa, V. Golovach, Y. Hirayama, D. Loss, T. Saku, R. Schouten and S. Tarucha for technical support and discussions. This work was supported by the DARPA-QUIST programme, the ONR, the EU-RTN network on spintronics and the Dutch Organisation for Fundamental Research on Matter (FOM).

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Correspondence to L. M. K. Vandersypen.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Figure 1

Scanning electron micrograph of the device, showing all the Ti-Au gates on top of a GaAs/Al0.27Ga0.73As heterostructure. (PDF 91 kb)

Supplementary Figure 2

Tuning the quantum dot into the spin read-out configuration. (PDF 461 kb)

Supplementary Figure 3

Setting the injection threshold. (PDF 33 kb)

Supplementary Figure 4

Measurement of the spin-relaxation time as in Fig. 3c, but at different magnetic fields. (PDF 14 kb)

Supplementary Figure Legends

Legends to supplementary Figures1 - 4. (DOC 31 kb)

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Elzerman, J., Hanson, R., Willems van Beveren, L. et al. Single-shot read-out of an individual electron spin in a quantum dot. Nature 430, 431–435 (2004).

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