Multiqubit GHZ state preparation with ${}^{1}71{\text{textYb}}^{+}$ ions for frequency standards

Abstract

Multiqubit Greenberger-Horne-Zeilinger (GHZ) state preparation is demonstrated on two to eight qubits in the chain of ten ${}^{171}Y{b}^{+}$ ions in the linear Paul trap with a sequence of single-qubit and two-qubit operations and pulsed dynamical decupling. Fidelity of the 8-qubit GHZ state is estimated to be $58.9\pm 0.6\%$. The expected enhanced sensitivity of the parity oscillations phase to the analyzing pulse phase is observed. This result is a step towards a multi-ion optical clock with ytterbium ions with frequency averaging following $1/N$ scaling law in contrast to the slower $1/\sqrt{N}$ scaling for an ensemble of independent particles in case when the decoherence is dominated by the spontaneous decay.