Quantum-state tomography is used to characterize the state of an ensemble based qubit implemented through two hyperfine levels in Pr3+ ions, doped into a Y2SiO5 crystal. We experimentally verify that single-qubit rotation errors due to inhomogeneities of the ensemble can be suppressed using the Roos-Molmer dark-state scheme [Roos and Molmer, Phys. Rev. A 69, 022321 (2004)] Fidelities above > 90%, presumably limited by excited state decoherence, were achieved. Although not explicitly taken care of in the Roos-Molmer scheme, it appears that also decoherence due to inhomogeneous broadening on the hyperfine transition is largely suppressed.
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机译：量子态层析成像用于表征通过掺入Y2SiO5晶体的Pr3 +离子中的两个超精细能级实现的基于整体的量子比特的状态。我们通过实验验证了使用Roos-Molmer暗态方案可以抑制由于整体不均匀导致的单量子位旋转错误[Roos and Molmer，Phys。 Rev. A 69，022321（2004）]实现了保真度大于90％（可能受激发态退相干性限制）的情况。尽管在Roos-Molmer方案中没有明确考虑，但似乎也大大抑制了由于超细转变上不均匀加宽引起的退相干。
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