Optimal tuning of solid-state quantum gates: A universal two-qubit gate

We present a general route to reduce inhomogeneous broadening in nanodevices due to 1/f noise. We apply this method to a universal two-qubit gate and demonstrate that for selected optimal couplings, a high-efficient gate can be implemented even in the presence of 1/f noise. Entanglement degradation due to interplay of 1/f and quantum noise is quantified via the concurrence. A charge-phase $\sqrt{{\rm i-SWAP}}$ gate for spectra extrapolated from single qubit experiments is analyzed.