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Superconducting nanocircuits for topologically protected qubits

Nature Physics volume 5, pages 48–53 (2009)Cite this article

Abstract

For successful realization of a quantum computer, its building blocks—the individual qubits—should be simultaneously scalable and sufficiently protected from environmental noise. Recently, a novel approach to the protection of superconducting qubits has been proposed. The idea is to prevent errors at the hardware level, by building a fault-free logical qubit from ‘faulty’ physical qubits with properly engineered interactions between them. The decoupling of such a topologically protected logical qubit from local noises is expected to grow exponentially with the number of physical qubits. Here, we report on proof-of-concept experiments with a prototype device that consists of twelve physical qubits made of nanoscale Josephson junctions. We observed that owing to properly tuned quantum fluctuations, this qubit is protected against magnetic flux variations well beyond linear order, in agreement with theoretical predictions. These results suggest that topologically protected superconducting qubits are feasible.

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Figure 1: Protected qubit based on ‘c o s(2φ)’ Josephson elements.
Figure 2: The prototype of a protected superconducting qubit.
Figure 3: Coherent transport of pairs of Cooper pairs.
Figure 4: Characteristic energies 2E2 and Δ2 for the devices with different values of EJ/EC.
Figure 5: Gate voltage dependence of the switching current.

References

  1. Steane, A. M. Overhead and noise threshold of fault-tolerant quantum error correction. Phys. Rev. A 68, 042322 (2003).

    Article  ADS  Google Scholar 

  2. Knill, E. Quantum computing with realistically noisy devices. Nature 434, 39–44 (2005).

    Article  ADS  Google Scholar 

  3. Steffen, M. et al. Measurements of the entanglement of two superconducting qubits via state tomography. Science 313, 1423–1425 (2006).

    Article  ADS  MathSciNet  Google Scholar 

  4. Yoshihara, F. et al. Decoherence of flux qubits due to 1/f flux noise. Phys. Rev. Lett. 97, 167001 (2006).

    Article  ADS  Google Scholar 

  5. Schreier, J. A. et al. Suppressing charge noise decoherence in superconducting charge qubits. Phys. Rev. B 77, 180502(R) (2008).

    Article  ADS  Google Scholar 

  6. Ithier, G. et al. Decoherence in a superconducting quantum bit circuit. Phys. Rev. B 72, 134519 (2005).

    Article  ADS  Google Scholar 

  7. Faoro, L. & Ioffe, L. B. Quantum two level systems and Kondo-like traps as possible sources of decoherence in superconducting qubits. Phys. Rev. Lett. 96, 047001 (2006).

    Article  ADS  Google Scholar 

  8. Faoro, L. & Ioffe, L. B. Microscopic origin of critical current fluctuations in large, small, and ultra-small area Josephson junctions. Phys. Rev. B 75, 132505 (2007).

    Article  ADS  Google Scholar 

  9. Aharonov, D., Kitaev, A. & Preskill, J. Fault-tolerant quantum computing with long-range correlated noise. Phys. Rev. Lett. 96, 050504 (2006).

    Article  ADS  Google Scholar 

  10. Aliferis, P., Gottesman, D. & Preskill, J. Quantum accuracy threshold for concatenated distance-3 codes. Quantum Inform. Comput. 6, 97–165 (2006).

    MathSciNet  MATH  Google Scholar 

  11. Oh, S. et al. Elimination of two level fluctuators in superconducting quantum bits by an epitaxial tunnel barrier. Phys. Rev. B 74, 100502(R) (2006).

    Article  ADS  Google Scholar 

  12. Martinis, J. M. et al. Decoherence in Josephson qubits from dielectric loss. Phys. Rev. Lett. 95, 210503 (2005).

    Article  ADS  Google Scholar 

  13. Vion, D. et al. Manipulating the quantum state of an electrical circuit. Science 296, 886–889 (2002).

    Article  ADS  Google Scholar 

  14. Chioresku, I., Nakamura, Y., Harmans, C. J. P. M. & Mooij, J. E. Coherent quantum dynamics of a superconducting flux qubit. Science 299, 1869–1871 (2003).

    Article  ADS  Google Scholar 

  15. Pashkin, Yu. A. et al. Quantum oscillations in two coupled charge qubits. Nature 421, 823–826 (2003).

    Article  ADS  Google Scholar 

  16. Wallraff, A. et al. Strong coupling of a single photon to a superconducting qubit using circuit quantum electrodynamics. Nature 431, 162–167 (2004).

    Article  ADS  Google Scholar 

  17. Kitaev, A.Yu. Fault-tolerant quantum computation by anyons. Ann. Phys. 303, 2–30 (2003).

    Article  ADS  MathSciNet  Google Scholar 

  18. Ioffe, L. B. & Feigelman, M. V. Possible realization of an ideal quantum computer in Josephson junction array. Phys. Rev. B 66, 224503 (2002).

    Article  ADS  Google Scholar 

  19. Doucot, B., Feigelman, M. V. & Ioffe, L. B. Topological order in the insulating Josephson junction arrays. Phys. Rev. Lett. 90, 107003 (2003).

    Article  ADS  Google Scholar 

  20. Doucot, B., Feigelman, M. V., Ioffe, L. B. & Ioselevich, A. S. Protected qubits and Chern-Simons theories in Josephson junction arrays. Phys. Rev. B 71, 024505 (2005).

    Article  ADS  Google Scholar 

  21. Blatter, G., Geshkenbein, V. B. & Ioffe, L. B. Design aspects of superconducting-phase quantum bits. Phys. Rev. B 63, 174511 (2001).

    Article  ADS  Google Scholar 

  22. Doucot, B. & Vidal, J. Pairing of cooper pairs in a fully frustrated Josephson-junction chain. Phys. Rev. Lett. 88, 227005 (2002).

    Article  ADS  Google Scholar 

  23. Protopopov, I. V. & Feigelman, M. V. Anomalous periodicity of supercurrent in long frustrated Josephson-junction rhombi chains. Phys. Rev. B 70, 184519 (2004).

    Article  ADS  Google Scholar 

  24. Tinkham, M. Introduction to Superconductivity 2nd edn (Dover, 1996).

    Google Scholar 

  25. Doucot, B. & Ioffe, L. B. Voltage–current curves for small Josephson junction arrays: Semiclassical treatment. Phys. Rev. B 76, 214507 (2007).

    Article  ADS  Google Scholar 

  26. Pop, I. M. et al. Measurement of the current-phase relation in Josephson junction rhombi chains. Phys. Rev. B 78, 104504 (2008).

    Article  ADS  Google Scholar 

  27. Kitaev, A. Protected qubit based on a superconducting current mirror. Preprint at <http://arxiv.org/abs/cond-mat/0609441> (2006).

  28. Corlevi, S., Guichard, W., Hekking, F. & Haviland, D. B. Phase-charge duality of a Josephson junction in a fluctuating electromagnetic environment. Phys. Rev. Lett. 97, 096802 (2006).

    Article  ADS  Google Scholar 

  29. Gottesman, D., Kitaev, A. & Preskill, J. Encoding a qubit in an oscillator. Phys. Rev. A 64, 012310 (2001).

    Article  ADS  Google Scholar 

  30. Bravyi, S. & Kitaev, A. Universal quantum computation with ideal Clifford gates and noisy ancillas. Phys. Rev. A 71, 022316 (2005).

    Article  ADS  MathSciNet  Google Scholar 

  31. Lichtenberger, A. W. et al. Fabrication of Nb/Al–Al2O3/Nb junctions with extremely low leakage currents. IEEE Trans. Magn. 25, 1247–1250 (1989).

    Article  ADS  Google Scholar 

  32. Lutchyn, R. M., Glazman, L. I. & Larkin, A. I. Kinetics of the superconducting charge qubit in the presence of a quasiparticle. Phys. Rev. B 74, 064515 (2006).

    Article  ADS  Google Scholar 

  33. Aumentado, J., Keller, M. W., Martinis, J. M. & Devoret, M. H. Nonequilibrium quasiparticles and 2e periodicity in single-Cooper-pair transistors. Phys. Rev. Lett. 92, 066802 (2004).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank J. Sanchez and S. Pereverzev for help with experiments and O. Buisson, W. Guichard, L. Faoro, M. Feigelman, B. Pannetier and V. Schmidt for stimulating discussions. The work at Rutgers University was supported in part by the NSF grant ECS-0608842 and the Rutgers Academic Excellence Fund. The work at the University of Paris has been partly supported by the ANR grant ANR-06BLAN-0218-01.

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Authors and Affiliations

  1. Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA

    Sergey Gladchenko, David Olaya, Eva Dupont-Ferrier, Lev B. Ioffe & Michael E. Gershenson

  2. Laboratoire de Physique Théorique et Hautes Energies, CNRS UMR 7589, Universités Paris 6 et 7, 4 place Jussieu, 75005 Paris, France

    Benoit Douçot

Authors
  1. Sergey Gladchenko
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Correspondence to Michael E. Gershenson.

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Gladchenko, S., Olaya, D., Dupont-Ferrier, E. et al. Superconducting nanocircuits for topologically protected qubits. Nature Phys 5, 48–53 (2009). https://doi.org/10.1038/nphys1151

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