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arXiv · 1606.07220

A long-lived Zeeman trapped-ion qubit

Thomas Ruster·Christian T. Schmiegelow·Henning Kaufmann·Claudia Warschburger·Ferdinand Schmidt-Kaler·Ulrich G. Poschinger
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Abstract

We demonstrate a coherence time of 2.1(1)~s for electron spin superposition states of a single trapped $^{40}$Ca$^+$ ion. The coherence time, measured with a spin-echo experiment, corresponds to residual rms magnetic field fluctuations $\leq$~2.7$\times$10$^{-12}$~T. 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 to 30~dB for frequencies of 50~Hz to 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 spin qubit to ultralong coherence times which so far have been observed only for magnetic insensitive transitions in atomic qubits with hyperfine structure.

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Thomas Ruster, Christian T. Schmiegelow, Henning Kaufmann, Claudia Warschburger, Ferdinand Schmidt-Kaler, Ulrich G. Poschinger. 2016-06-23. A long-lived Zeeman trapped-ion qubit. https://doi.org/10.1007/s00340-016-6527-4

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