High-Fidelity Trapped-Ion Quantum Logic Using Near-Field Microwaves
T. P. Harty, M. A. Sepiol, D. T. C. Allcock, Christopher J. Ballance, J. E. Tarlton, D. M. Lucas · Physical Review Letters · 2016
We demonstrate a two-qubit logic gate driven by near-field microwaves in a room-temperature microfabricated surface ion trap. We introduce a dynamically decoupled gate method, which stabilizes the qubits against fluctuating energy shifts and avoids the need to null the microwave field. We use the gate to produce a Bell state with fidelity 99.7(1)%, after accounting for state preparation and measurement errors. The gate is applied directly to ^{43}Ca^{+} hyperfine "atomic clock" qubits (coherence time T_{2}^{*}≈50 s) using the oscillating magnetic field gradient produced by an integrated microwave electrode.