Skip to main content

Thank you for visiting nature.com. 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.

High-fidelity laser-free universal control of trapped ion qubits

Abstract

Universal control of multiple qubits—the ability to entangle qubits and to perform arbitrary individual qubit operations1—is a fundamental resource for quantum computing2, simulation3 and networking4. Qubits realized in trapped atomic ions have shown the highest-fidelity two-qubit entangling operations5,6,7 and single-qubit rotations8 so far. Universal control of trapped ion qubits has been separately demonstrated using tightly focused laser beams9,10,11,12 or by moving ions with respect to laser beams13,14,15, but at lower fidelities. Laser-free entangling methods16,17,18,19,20 may offer improved scalability by harnessing microwave technology developed for wireless communications, but so far their performance has lagged the best reported laser-based approaches. Here we demonstrate high-fidelity laser-free universal control of two trapped-ion qubits by creating both symmetric and antisymmetric maximally entangled states with fidelities of \({1}_{-0.0017}^{+0}\) and \({0.9977}_{-0.0013}^{+0.0010}\), respectively (68 per cent confidence level), corrected for initialization error. We use a scheme based on radiofrequency magnetic field gradients combined with microwave magnetic fields that is robust against multiple sources of decoherence and usable with essentially any trapped ion species. The scheme has the potential to perform simultaneous entangling operations on multiple pairs of ions in a large-scale trapped-ion quantum processor without increasing control signal power or complexity. Combining this technology with low-power laser light delivered via trap-integrated photonics21,22 and trap-integrated photon detectors for qubit readout23,24 provides an opportunity for scalable, high-fidelity, fully chip-integrated trapped-ion quantum computing.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Experimental setup.
Fig. 2: Robustness of entangling operation.
Fig. 3: Entangled-state fidelity analysis.

Data availability

Source data are provided with this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Code availability

All simulation code or analysis code that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

References

  1. 1.

    Barenco, A. et al. Elementary gates for quantum computation. Phys. Rev. A 52, 3457–3467 (1995).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  2. 2.

    Jozsa, R. in The Geometric Universe: Science, Geometry, and the work of Roger Penrose (eds Huggett, S. A, Mason, L. J., Tod, K. P., Tsou, S. T. & Woodhouse, N. M. J.) 369 (Oxford Univ. Press, 1998).

  3. 3.

    Georgescu, I. M., Ashhab, S. & Nori, F. Quantum simulation. Rev. Mod. Phys. 86, 153–185 (2014).

    ADS  Article  Google Scholar 

  4. 4.

    Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  5. 5.

    Ballance, C. J., Harty, T. P., Linke, N. M., Sepiol, M. A. & Lucas, D. M. High-fidelity quantum logic gates using trapped-ion hyperfine qubits. Phys. Rev. Lett. 117, 060504 (2016).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  6. 6.

    Gaebler, J. P. et al. High-fidelity universal gate set for 9Be+ ion qubits. Phys. Rev. Lett. 117, 060505 (2016).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  7. 7.

    Clark, C. R. et al. High-fidelity Bell-state preparation with 40Ca+ optical qubits. Preprint at https://arxiv.org/abs/2105.05828 (2021).

  8. 8.

    Harty, T. P. et al. High-fidelity preparation, gates, memory, and readout of a trapped-ion quantum bit. Phys. Rev. Lett. 113, 220501 (2014).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  9. 9.

    Schmidt-Kaler, F. et al. Realization of the Cirac–Zoller controlled-NOT quantum gate. Nature 422, 408–411 (2003).

    ADS  CAS  PubMed  Article  Google Scholar 

  10. 10.

    Debnath, S. et al. Demonstration of a small programmable quantum computer with atomic qubits. Nature 536, 63–66 (2016).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  11. 11.

    Wright, K. et al. Benchmarking an 11-qubit quantum computer. Nat. Commun. 10, 5464 (2019).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  12. 12.

    Erhard, A. et al. Characterizing large-scale quantum computers via cycle benchmarking. Nat. Commun. 10, 5347 (2019).

    ADS  PubMed  PubMed Central  Article  Google Scholar 

  13. 13.

    Barrett, M. D. et al. Deterministic quantum teleportation of atomic qubits. Nature 429, 737–739 (2004).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  14. 14.

    Ruster, T. et al. Entanglement-based dc magnetometry with separated ions. Phys. Rev. X 7, 031050 (2017).

    Google Scholar 

  15. 15.

    Pino, J. M. et al. Demonstration of the trapped-ion quantum CCD computer architecture. Nature 592, 209–213 (2021).

  16. 16.

    Wineland, D. J. et al. Experimental issues in coherent quantum-state manipulation of trapped atomic ions. J. Res. Natl Inst. Stand. Technol. 103, 259–328 (1998).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  17. 17.

    Mintert, F. & Wunderlich, C. Ion-trap quantum logic using long-wavelength radiation. Phys. Rev. Lett. 87, 257904 (2001).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  18. 18.

    Ospelkaus, C. et al. Trapped-ion quantum logic gates based on oscillating magnetic fields. Phys. Rev. Lett. 101, 090502 (2008).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  19. 19.

    Harty, T. P. et al. High-fidelity trapped-ion quantum logic using near-field microwaves. Phys. Rev. Lett. 117, 140501 (2016).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  20. 20.

    Zarantonello, G. et al. Robust and resource-efficient microwave near-field entangling 9Be+ gate. Phys. Rev. Lett. 123, 260503 (2019).

    ADS  CAS  PubMed  Article  Google Scholar 

  21. 21.

    Mehta, K. K. et al. Integrated optical multi-ion quantum logic. Nature 586, 533–537 (2020).

    ADS  CAS  PubMed  Article  Google Scholar 

  22. 22.

    Niffenegger, R. J. et al. Integrated multi-wavelength control of an ion qubit. Nature 586, 538–542 (2020).

    ADS  CAS  PubMed  Article  Google Scholar 

  23. 23.

    Todaro, S. L. et al. State readout of a trapped ion qubit using a trap-integrated superconducting photon detector. Phys. Rev. Lett. 126, 010501 (2021).

    ADS  CAS  PubMed  Article  Google Scholar 

  24. 24.

    Setzer, W. et al. Fluorescence detection of a trapped ion with a monolithically integrated single-photon-counting avalanche diode. Preprint at https://arxiv.org/abs/2105.01235 (2021).

  25. 25.

    Cirac, J. I. & Zoller, P. Quantum computations with cold trapped ions. Phys. Rev. Lett. 74, 4091 (1995).

    ADS  CAS  PubMed  Article  Google Scholar 

  26. 26.

    Milburn, G. J., Schneider, S. & James, D. F. V. Ion trap quantum computing with warm ions. Fortschr. Phys. 48, 801–810 (2000).

    CAS  Article  Google Scholar 

  27. 27.

    Sørensen, A. & Mølmer, K. Quantum computation with ions in thermal motion. Phys. Rev. Lett. 82, 1971–1974 (1999).

    ADS  Article  Google Scholar 

  28. 28.

    Sørensen, A. & Mølmer, K. Entanglement and quantum computation with ions in thermal motion. Phys. Rev. A 62, 022311 (2000).

    ADS  Article  Google Scholar 

  29. 29.

    Leibfried, D., Blatt, R., Monroe, C. & Wineland, D. Quantum dynamics of single trapped ions. Rev. Mod. Phys. 75, 281–324 (2003).

    ADS  CAS  Article  Google Scholar 

  30. 30.

    Nägerl, H. C. et al. Laser addressing of individual ions in a linear ion trap. Phys. Rev. A 60, 145 (1999).

    ADS  Article  Google Scholar 

  31. 31.

    Monroe, C., Meekhof, D. M., King, B. E., Itano, W. M. & Wineland, D. J. Demonstration of a fundamental quantum logic gate. Phys. Rev. Lett. 75, 4714–4717 (1995).

    ADS  MathSciNet  CAS  PubMed  MATH  Article  PubMed Central  Google Scholar 

  32. 32.

    Leibfried, D. et al. Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate. Nature 422, 412–415 (2003).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  33. 33.

    Ozeri, R. et al. Errors in trapped-ion quantum gates due to spontaneous photon scattering. Phys. Rev. A 75, 042329 (2007).

    ADS  Article  CAS  Google Scholar 

  34. 34.

    Ospelkaus, C. et al. Microwave quantum logic gates for trapped ions. Nature 476, 181–184 (2011).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  35. 35.

    Hahn, H. et al. Integrated 9Be+ multi-qubit gate device for the ion-trap quantum computer. npj Quantum Inf. 5, 70 (2019).

    ADS  Article  Google Scholar 

  36. 36.

    Khromova, A. et al. Designer spin pseudomolecule implemented with trapped ions in a magnetic gradient. Phys. Rev. Lett. 108, 220502 (2012).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  37. 37.

    Weidt, S. et al. Trapped-ion quantum logic with global radiation fields. Phys. Rev. Lett. 117, 220501 (2016).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  38. 38.

    Leibfried, D. Individual addressing and state readout of trapped ions utilizing rf micromotion. Phys. Rev. A 60, R3335 (1999).

    ADS  CAS  Article  Google Scholar 

  39. 39.

    Johanning, M. et al. Individual addressing of trapped ions and coupling of motional and spin states using rf radiation. Phys. Rev. Lett. 102, 073004 (2009).

    ADS  CAS  PubMed  Article  Google Scholar 

  40. 40.

    Warring, U. et al. Individual-ion addressing with microwave field gradients. Phys. Rev. Lett. 110, 173002 (2013).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  41. 41.

    Sutherland, R. T. et al. Versatile laser-free trapped-ion entangling gates. New J. Phys. 21, 033033 (2019).

    ADS  CAS  Article  Google Scholar 

  42. 42.

    Hayes, D. et al. Coherent error suppression in multiqubit entangling gates. Phys. Rev. Lett. 109, 020503 (2012).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  43. 43.

    Srinivas, R. et al. Trapped-ion spin-motion coupling with microwaves and a near-motional oscillating magnetic field gradient. Phys. Rev. Lett. 122, 163201 (2019).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  44. 44.

    Sackett, C. A. et al. Experimental entanglement of four particles. Nature 404, 256–259 (2000).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  45. 45.

    Sutherland, R. T. et al. Laser-free trapped-ion entangling gates with simultaneous insensitivity to qubit and motional decoherence. Phys. Rev. A 101, 042334 (2020).

    ADS  CAS  Article  Google Scholar 

  46. 46.

    Emerson, J., Alicki, R. & Życzkowski, K. Scalable noise estimation with random unitary operators. J. Opt. B 7, S347–S352 (2005).

    ADS  MathSciNet  Article  Google Scholar 

  47. 47.

    Knill, E. et al. Randomized benchmarking of quantum gates. Phys. Rev. A 77, 012307 (2008).

    ADS  Article  CAS  Google Scholar 

  48. 48.

    Piltz, C., Sriarunothai, T., Varón, A. F. & Wunderlich, C. A trapped-ion-based quantum byte with 10−5 next-neighbour cross-talk. Nat. Commun. 5, 4679 (2014).

    ADS  CAS  PubMed  Article  Google Scholar 

  49. 49.

    Aude Craik, D. P. L. et al. High-fidelity spatial and polarization addressing of 43Ca+ qubits using near-field microwave control. Phys. Rev. A 95, 022337 (2017).

    ADS  Article  Google Scholar 

  50. 50.

    Leibfried, D., Knill, E., Ospelkaus, C. & Wineland, D. J. Transport quantum logic gates for trapped ions. Phys. Rev. A 76, 032324 (2007).

    ADS  Article  CAS  Google Scholar 

  51. 51.

    Kielpinski, D., Monroe, C. & Wineland, D. J. Architecture for a large-scale ion-trap quantum computer. Nature 417, 709 (2002).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  52. 52.

    Stuart, J. et al. Chip-integrated voltage sources for control of trapped ions. Phys. Rev. Appl. 11, 024010 (2019).

    ADS  CAS  Article  Google Scholar 

  53. 53.

    Chou, C.-W. et al. Preparation and coherent manipulation of pure quantum states of a single molecular ion. Nature 545, 164–165 (2017).

    ADS  Article  CAS  Google Scholar 

  54. 54.

    Kozlov, M. G., Safronova, M. S., Crespo López-Urrutia, J. R. & Schmidt, P. O. Highly charged ions: optical clocks and applications in fundamental physics. Rev. Mod. Phys. 90, 045005 (2018).

    ADS  CAS  Article  Google Scholar 

  55. 55.

    Matthiesen, C., Yu, Q., Guo, J., Alonso, A. M. & Häffner, H. Trapping electrons in a room-temperature microwave Paul trap. Phys. Rev. X 11, 011019 (2021).

    CAS  Google Scholar 

Download references

Acknowledgements

We thank C. J. Ballance, T. P. Harty, J. P. Gaebler, S. B. Libby, D. M. Lucas, V. M. Schäfer and T. R. Tan for helpful discussions. We thank M. Affolter and A. L. Collopy for insightful comments on the manuscript. At the time the work was performed, R.S., S.C.B., H.M.K., A.K., and D.T.C.A. were supported as associates in the Professional Research Experience Program (PREP) operated jointly by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder under award number 70NANB18H006 from the US Department of Commerce, NIST. This work was supported by the NIST Quantum Information Program and ONR.

Author information

Affiliations

Authors

Contributions

R.S. and H.M.K. carried out the experiments, assisted by S.C.B., D.T.C.A and D.H.S.; D.H.S., R.S., H.M.K., A.K. and R.T.S. analysed the data and performed numerical simulations, with support from E.K. and S.G.; D.T.C.A., D.H.S., R.S., S.C.B. and H.M.K. built and maintained the experimental apparatus; R.S. wrote the manuscript with input from all authors; A.C.W., D.L., D.H.S. and D.J.W. secured funding for the work; and D.H.S. and D.T.C.A. supervised the work with support from A.C.W., D.L., S.G., E.K. and D.J.W.

Corresponding authors

Correspondence to R. Srinivas or D. H. Slichter.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Tracy Northup, Christian Roos and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

This file contains Supplementary Sections 1–4, including Supplementary Figs. 1–5, Table 1 and References.

Source Data

This file contains source data for Supplementary Fig. 3.

Source Data

This file contains source data for Supplementary Fig. 4.

Source Data

This file contains source data for Supplementary Fig. 5.

Peer Review File

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Srinivas, R., Burd, S.C., Knaack, H.M. et al. High-fidelity laser-free universal control of trapped ion qubits. Nature 597, 209–213 (2021). https://doi.org/10.1038/s41586-021-03809-4

Download citation

Further reading

Comments

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.

Search

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