  We investigate the possibility to achieve high-fidelity universal two-qubit
gates by supplementing optimal tuning of individual qubits with dynamical
decoupling (DD) of local 1/f noise. We consider simultaneous local pulse
sequences applied during the gate operation and compare the efficiencies of
periodic, Carr-Purcell and Uhrig DD with hard $\pi$-pulses along two directions
($\pi_{z/y}$ pulses). We present analytical perturbative results (Magnus
expansion) in the quasi-static noise approximation combined with numerical
simulations for realistic 1/f noise spectra. The gate efficiency is studied as
a function of the gate duration, of the number $n$ of pulses, and of the
high-frequency roll-off. We find that the gate error is non-monotonic in $n$,
decreasing as $n^{-\alpha}$ in the asymptotic limit, $\alpha \geq 2$ depending
on the DD sequence. In this limit $\pi_z$-Urhig is the most efficient scheme
for quasi-static 1/f noise, but it is highly sensitive to the soft UV-cutoff.
For small number of pulses, $\pi_z$ control yields anti-Zeno behavior, whereas
$\pi_y$ pulses minimize the error for a finite $n$. For the current noise
figures in superconducting qubits, two-qubit gate errors $\sim 10^{-6}$,
meeting the requirements for fault-tolerant quantum computation, can be
achieved. The Carr-Purcell-Meiboom-Gill sequence is the most efficient
procedure, stable for $1/f$ noise with UV-cutoff up to gigahertz.
