  We present a model of a qubit built of a three coherently coupled quantum
dots with three spins in a triangular geometry. The qubit states are encoded in
the doublet subspace and they are controlled by a gate voltage, which breaks
the triangular symmetry of the system. We show how to prepare the qubit and to
perform one qubit operations. A new type of the current blockade effect will be
discussed. The blockade is related with an asymmetry of transfer rates from the
electrodes to different doublet states and is used to read-out of the dynamics
of the qubit state. Our research also presents analysis of the Rabi
oscillations, decoherence and leakage processes in the doublets subspace.
