No abstract

We present the experimental implementation of a two-qubit phase gate,&#xD;using a radio frequency (RF) controlled trapped-ion quantum processor. The RFdriven&#xD;gate is generated by a pulsed dynamical decoupling sequence applied to the&#xD;ions’ carrier transitions only. It allows for a tunable phase shift with high-fidelity&#xD;results. The conditional phase shift is measured using a Ramsey-type measurement&#xD;with an inferred fringe contrast of up to 99+1&#xD;−2%. We also prepare a Bell state using&#xD;this laser-free gate. The phase gate is robust against common sources of error. We&#xD;investigate the effect of the excitation of the center-of-mass (COM) mode, errors in the&#xD;axial trap frequency, pulse area errors and errors in sequence timing. The contrast of&#xD;the phase gate is not significantly reduced up to a COM mode excitation < 20 phonons,&#xD;trap frequency errors of +10%, and pulse area errors of -8%. The phase shift is&#xD;not significantly affected up to < 10 phonons and pulse area errors of -2%. Both,&#xD;contrast and phase shift are robust to timing errors up to -30% and +15%. The gate&#xD;implementation is resource efficient, since only a single driving field is required per&#xD;ion. Furthermore, it holds the potential for fast gate speeds (gate times on the order&#xD;of 100 μs) by using two axial motional modes of a two-ion crystal through improved&#xD;setups.