  An ultrafast qubit control concept is proposed to reduce the duration of
operations with a single and multiple superconducting qubits. It is based on
the generation of Ramsey fringes due to unipolar picosecond control pulses. The
key role in the concept is played by the interference of waves of qubit states
population propagating forward and backward in time. The influence of the shape
and duration of control pulses on the contrast of the interference pattern is
revealed in the frame of Ramsey's paradigm. Protocols for observation of Ramsey
oscillations and implementation of various gate operations are developed. We
also suggest a notional engineering solution for creating the required
picosecond control pulses with desired shape and amplitude. It is demonstrated
that this makes it possible to control the quantum states of the system with
the fidelity of more than 99%.
