  The development of quantum computers based on superconductors requires the
improvement of the qubit state control approach aimed at the increase of the
hardware energy efficiency. A promising solution to this problem is the use of
superconducting digital circuits operating with single-flux-quantum (SFQ)
pulses, moving the qubit control system into the cold chamber. However, the
qubit gate time under SFQ control is still longer than under conventional
microwave driving. Here we introduce the bipolar SFQ pulse control based on
ternary pulse sequences. We also develop a robust optimization algorithm for
finding a sequence structure that minimizes the leakage of the transmon qubit
state from the computational subspace. We show that the appropriate sequence
can be found for arbitrary system parameters from the practical range. The
proposed bipolar SFQ control reduces a single qubit gate time by halve compared
to nowadays unipolar SFQ technique, while maintaining the gate fidelity over
99.99%.
