Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Exciting Andreev pairs in a superconducting atomic contact

An Erratum to this article was published on 18 December 2013

This article has been updated


The Josephson effect describes the flow of supercurrent in a weak link—such as a tunnel junction, nanowire or molecule—between two superconductors1. It is the basis for a variety of circuits and devices, with applications ranging from medicine2 to quantum information3. Experiments using Josephson circuits that behave like artificial atoms4 are now revolutionizing the way we probe and exploit the laws of quantum physics5,6. Microscopically, the supercurrent is carried by Andreev pair states, which are localized at the weak link. These states come in doublets and have energies inside the superconducting gap7,8,9,10. Existing Josephson circuits are based on properties of just the ground state of each doublet, and so far the excited states have not been directly detected. Here we establish their existence through spectroscopic measurements of superconducting atomic contacts. The spectra, which depend on the atomic configuration and on the phase difference between the superconductors, are in complete agreement with theory. Andreev doublets could be exploited to encode information in novel types of superconducting qubits11,12,13.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Principles of spectroscopy of the Andreev transition.
Figure 2: IJ(VJ) characteristics of the spectrometer coupled to the SQUID with atomic contact AC2.
Figure 3: Absorption spectra for three atomic contacts.
Figure 4: Interpretation of the absorption spectra.

Change history


  1. Josephson, B. D. Possible new effects in superconductive tunnelling. Phys. Lett. 1, 251–253 (1962)

    Article  ADS  Google Scholar 

  2. Busch, S. et al. Measurements of T1-relaxation in ex vivo prostate tissue at 132 μT. Magn. Reson. Med. 67, 1138–1145 (2012)

    Article  ADS  Google Scholar 

  3. Erik Lucero et al. High-fidelity gates in a single Josephson qubit. Nature Phys. 8, 719–723 (2012)

  4. Wendin, G. & Shumeiko, V. S. Quantum bits with Josephson junctions. Low Temp. Phys. 33, 724–744 (2007)

    CAS  Article  ADS  Google Scholar 

  5. Fink, J. M. et al. Climbing the Jaynes–Cummings ladder and observing its nonlinearity in a cavity QED system. Nature 454, 315–318 (2008)

    CAS  Article  ADS  Google Scholar 

  6. Hofheinz, M. et al. Synthesizing arbitrary quantum states in a superconducting resonator. Nature 459, 546–549 (2009)

    CAS  Article  ADS  Google Scholar 

  7. Kulik, I. O. Macroscopic quantization and proximity effect in S-N-S junctions. Sov. Phys. JETP 30, 944–950 (1970)

    ADS  Google Scholar 

  8. Furusaki, A. & Tsukada, M. Dc Josephson effect and Andreev reflection. Solid State Commun. 78, 299–302 (1991)

    Article  ADS  Google Scholar 

  9. Beenakker, C. W. J. & van Houten, H. Josephson current through a superconducting quantum point contact shorter than the coherence length. Phys. Rev. Lett. 66, 3056–3059 (1991)

    CAS  Article  ADS  Google Scholar 

  10. Bagwell, P. F. Suppression of the Josephson current through a narrow, mesoscopic, semiconductor channel by a single impurity. Phys. Rev. B 46, 12573–12586 (1992)

    CAS  Article  ADS  Google Scholar 

  11. Zazunov, A., Shumeiko, V. S., Bratus’, E. N., Lantz, J. & Wendin, G. Andreev level qubit. Phys. Rev. Lett. 90, 087003 (2003)

    CAS  Article  ADS  Google Scholar 

  12. Chtchelkatchev, N. M. & Nazarov, V. Andreev quantum dots for spin manipulation. Phys. Rev. Lett. 90, 226806 (2003)

    Article  ADS  Google Scholar 

  13. Padurariu, C. & Nazarov, V. Spin blockade qubit in a superconducting junction. Europhys. Lett. 100, 57006–57011 (2012)

    CAS  Article  ADS  Google Scholar 

  14. Bardeen, J., Cooper, L. N. & Schrieffer, J. R. Theory of superconductivity. Phys. Rev. 108, 1175–1204 (1957)

    MathSciNet  CAS  Article  ADS  Google Scholar 

  15. Della Rocca, M. L. et al. Measurement of the current-phase relation of superconducting atomic contacts. Phys. Rev. Lett. 99, 127005 (2007)

    CAS  Article  ADS  Google Scholar 

  16. Zgirski, M. et al. Evidence for long-lived quasiparticles trapped in superconducting point contacts. Phys. Rev. Lett. 106, 257003 (2011)

    CAS  Article  ADS  Google Scholar 

  17. Deacon, R. S. et al. Tunneling spectroscopy of Andreev energy levels in a quantum dot coupled to a superconductor. Phys. Rev. Lett. 104, 076805 (2010)

    CAS  Article  ADS  Google Scholar 

  18. Pillet, J.-D. et al. Andreev bound states in supercurrent-carrying carbon nanotubes revealed. Nature Phys. 6, 965–969 (2010)

    CAS  Article  ADS  Google Scholar 

  19. Morpurgo, A. F., Baselmans, J. J. A., van Wees, B. J. & Klapwijk, T. M. Energy spectroscopy of the Josephson supercurrent. J. Low Temp. Phys. 118, 637–651 (2000)

    CAS  Article  ADS  Google Scholar 

  20. Fuechsle, M. et al. Effect of microwaves on the current-phase relation of superconductor normal-metal superconductor Josephson junctions. Phys. Rev. Lett. 102, 127001 (2009)

    CAS  Article  ADS  Google Scholar 

  21. van Ruitenbeek, J. M. et al. Adjustable nanofabricated atomic size contacts. Rev. Sci. Instrum. 67, 108–111 (1996)

    CAS  Article  ADS  Google Scholar 

  22. Edstam, J. & Olsson, H. K. Josephson broadband spectroscopy to 1 THz. Appl. Phys. Lett. 64, 2733–2735 (1994)

    CAS  Article  ADS  Google Scholar 

  23. Leppäkangas, J., Thuneberg, E., Lindell, R. & Hakonen, P. Tunneling of Cooper pairs across voltage-biased asymmetric single-Cooper-pair transistors. Phys. Rev. B 74, 054504 (2006)

    Article  ADS  Google Scholar 

  24. Billangeon, P.-M., Pierre, F., Bouchiat, H. & Deblock, R. Very high frequency spectroscopy and tuning of a single-Cooper-pair transistor with an on-chip generator. Phys. Rev. Lett. 98, 126802 (2007)

    Article  ADS  Google Scholar 

  25. Scheer, E., Joyez, P., Esteve, D., Urbina, C. & Devoret, M. H. Conduction channel transmissions of atomic-size aluminum contacts. Phys. Rev. Lett. 78, 3535–3538 (1997)

    CAS  Article  ADS  Google Scholar 

  26. Holst, T., Esteve, D., Urbina, C. & Devoret, M. H. Effect of a transmission line resonator on a small capacitance tunnel junction. Phys. Rev. Lett. 73, 3455–3458 (1994)

    CAS  Article  ADS  Google Scholar 

  27. Hofheinz, M. et al. Bright side of the Coulomb blockade. Phys. Rev. Lett. 106, 217005 (2011)

    CAS  Article  ADS  Google Scholar 

  28. Romero, G., Lizuain, I., Shumeiko, V. S., Solano, E. & Bergeret, F. S. Circuit quantum electrodynamics with a superconducting quantum point contact. Phys. Rev. B 85, 180506 (2012)

    Article  ADS  Google Scholar 

  29. Sköldberg, J., Löfwander, T., Shumeiko, V. S. & Fogelström, M. Spectrum of Andreev bound states in a molecule embedded inside a microwave-excited superconducting junction. Phys. Rev. Lett. 101, 087002 (2008)

    Article  ADS  Google Scholar 

  30. Mourik, V. et al. Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices. Science 336, 1003–1007 (2012)

    CAS  Article  ADS  Google Scholar 

Download references


We acknowledge technical assistance from P. Sénat and P.-F. Orfila, theoretical input from M. Houzet, help in the experiments from L. Tosi, and discussions with V. Shumeiko, A. Levy-Yeyati and within the Quantronics group. This work was supported by ANR contracts DOCFLUC and MASH, and by C’Nano. The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. PIIF-GA-2011-298415.

Author information

Authors and Affiliations



All authors designed the experiment, L.B. and Ç.Ö.G. fabricated the sample, L.B., Ç.Ö.G., H.P. and C.U. carried out the measurements and analysed the data, and all authors contributed to the writing of the manuscript.

Corresponding author

Correspondence to C. Urbina.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-6, Supplementary Methods and additional references. (PDF 1217 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bretheau, L., Girit, Ç., Pothier, H. et al. Exciting Andreev pairs in a superconducting atomic contact. Nature 499, 312–315 (2013).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing