  We exploit hyperfine interactions in a single Mn-ion confined in a quantum
dot (QD) to create a qudit, i.e. a multi-level quantum-bit system, with well
defined, addressable and robust set of spin states for the realization of
universal quantum gates. We generate and probe an arbitrary superposition of
states between selected hyperfine energy level pairs by using electron double
resonance detected nuclear magnetic resonance (EDNMR). This enables the
observation of Rabi oscillations and the experimental realization of NOT and
SWAP universal quantum gates that are robust against decoherence. Our protocol
for cyclical preparation, manipulation and read-out of logic gates offers
opportunities for integration of qudits in scalable quantum circuit
architectures beyond solid state electron spin qubits.
