Applied Physics B

, 122:254 | Cite as

A long-lived Zeeman trapped-ion qubit

  • T. Ruster
  • C. T. Schmiegelow
  • H. Kaufmann
  • C. Warschburger
  • F. Schmidt-Kaler
  • U. G. PoschingerEmail author
Rapid Communication


We demonstrate unprecedentedly long lifetimes for electron spin superposition states of a single trapped \(^{40}\)Ca\(^+\) ion. For a Ramsey measurement, we achieve a \(1{/}\sqrt{e}\) coherence time of 300(50) ms, while a spin-echo experiment yields a coherence time of 2.1(1) s. The latter corresponds to residual effective rms magnetic field fluctuations \({\le }2.7\times 10^{-12}\,\hbox {T}\) during a measurement time of about 1500 s. The suppression of decoherence induced by fluctuating magnetic fields is achieved by combining a two-layer \(\mu\)-metal shield, which reduces external magnetic noise by 20–30 dB for frequencies of 50 Hz–100 kHz, with Sm\(_2\)Co\(_{17}\) permanent magnets for generating a quantizing magnetic field of 0.37 mT. Our results extend the coherence time of the simple-to-operate trapped-ion spin qubit to ultralong coherence times which so far have been observed only for magnetic insensitive transitions in atomic qubits with hyperfine structure.


Permanent Magnet Wait Time Coherence Time Zeeman Splitting Ambient Magnetic Field 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The use of permanent magnets was inspired during a visit of CTS and FSK at Tobias Schätz’ labs at Universität Freiburg. We acknowledge earlier contributions of Andrè Kesser for the characterization of the shielding properties of the \(\mu\)-metal enclosure. We further acknowledge helpful discussions with Georg Jacob and Sven Sturm. The research is based upon work supported by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via the US Army Research Office Grants W911NF-10-1-0284 and W911NF-16-1-0070. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA or the US Government. The US Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the view of the US Army Research Office.



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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • T. Ruster
    • 1
  • C. T. Schmiegelow
    • 1
    • 2
  • H. Kaufmann
    • 1
  • C. Warschburger
    • 1
  • F. Schmidt-Kaler
    • 1
  • U. G. Poschinger
    • 1
    Email author
  1. 1.Institut für PhysikUniversität MainzMainzGermany
  2. 2.Departamento de Física, FCEyN, UBA and IFIBA, Conicet, Pabellón 1, Ciudad UniversitariaBuenos AiresArgentina

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