Noise-resistant off-resonant π-rotation realized in an NMR system

Precise manipulation of qubits requires strong suppression of noises from couplings between qubits and their environment and driving field fluctuation. We propose a double-pulse sequence to realize arbitrary-angle single qubit rotation and an eighteen-pulse sequence to suppress both dephasing and driving field noise under off-resonant condition (instead of conventional on-resonance or near-resonant condition). By applying both sequences to an NMR spin system, we demonstrate experimentally the π-rotation fidelity reaches as high as 0.99921±0.00084 for the double-pulse sequence and 0.99974 ± 0.00057 for the eighteen-pulse sequence. In addition, the noise-tolerance range of the eighteen-pulse sequence is as about 3 times wide as that of the double-pulse sequence. Our proposal provides an alternative practical way to suppress the driving field noise.