High-Fidelity Readout of Trapped-Ion Qubits
A. H. Myerson, D. J. Szwer, S. C. Webster, D. T. C. Allcock, Michael J. Curtis, Gergely Imreh, Jeff A. Sherman, D. N. Stacey, Andrew M. Steane, D. M. Lucas · Physical Review Letters · 2008
We demonstrate single-shot qubit readout with a fidelity sufficient for fault-tolerant quantum computation. For an optical qubit stored in 40Ca+ we achieve 99.991(1)% average readout fidelity in 10(6) trials, using time-resolved photon counting. An adaptive measurement technique allows 99.99% fidelity to be reached in 145 micros average detection time. For 43Ca+, we propose and implement an optical pumping scheme to transfer a long-lived hyperfine qubit to the optical qubit, capable of a theoretical fidelity of 99.95% in 10 micros. We achieve 99.87(4)% transfer fidelity and 99.77(3)% net readout fidelity.