  Fully autonomous precise control of qubits is crucial for quantum information
processing, quantum communication, and quantum sensing applications. It
requires minimal human intervention on the ability to model, to predict and to
anticipate the quantum dynamics [1,2], as well as to precisely control and
calibrate single qubit operations. Here, we demonstrate single qubit autonomous
calibrations via closed-loop optimisations of electron spin quantum operations
in diamond. The operations are examined by quantum state and process
tomographic measurements at room temperature, and their performances against
systematic errors are iteratively rectified by an optimal pulse engineering
algorithm. We achieve an autonomous calibrated fidelity up to 1.00 on a time
scale of minutes for a spin population inversion and up to 0.98 on a time scale
of hours for a Hadamard gate within the experimental error of 2%. These results
manifest a full potential for versatile quantum nanotechnologies.
