Experimental quantum state tomography of a solid state qubit

TL;DR

This paper demonstrates quantum state tomography on a solid-state qubit, achieving high fidelity measurements and showing that certain errors can be suppressed using a specific dark state scheme.

Contribution

It introduces the application of the Roos-Moelmer dark state scheme to suppress rotation errors in solid-state qubits during tomography.

Findings

Fidelities above 90% were achieved.

Single-qubit rotation errors can be suppressed.

Decoherence effects are largely mitigated.

Abstract

Full 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-Moelmer dark state scheme. Fidelities above >90%, presumably limited by excited state decoherence, were achieved. Although not explicitly taken care of in the Roos-Moelmer scheme, it appears that also decoherence due to inhomogeneous broadening on the hyperfine transition is largely suppressed.