Noise filtering of composite pulses for singlet-triplet qubits
  Semiconductor quantum dot spin qubits are promising candidates for quantum computing. In these systems, the dynamically corrected gates offer considerable reduction of gate errors and are therefore of great interest both theoretically and experimentally. They are, however, designed under the static-noise model and may be considered as low-frequency filters. In this work, we perform a comprehensive theoretical study of the response of a type of dynamically corrected gates, namely the {\sc supcode} for singlet-triplet qubits, to realistic $1/f$ noises with frequency spectra $1/\omega^\alpha$. Through randomized benchmarking, we have found that {\sc supcode} offers improvement of the gate fidelity for $\alpha\gtrsim1$ and the improvement becomes exponentially more pronounced with the increase of the noise exponent in the range $1\lesssim\alpha\leq3$ studied. On the other hand, for small $\alpha$, {\sc supcode} will not offer any improvement. The $\delta J$-{\sc supcode}, specifically designed for systems where the nuclear noise is absent, is found to offer additional error reduction than the full {\sc supcode} for charge noises. The computed filter transfer functions of the {\sc supcode} gates are also presented. 
Xu-Chen Yang and Xin Wang
cond-mat.mes-hall quant-ph