Scalable in-situ qubit calibration during repetitive error detection
  We present a method to optimize qubit control parameters during error detection which is compatible with large-scale qubit arrays. We demonstrate our method to optimize single or two-qubit gates in parallel on a nine-qubit system. Additionally, we show how parameter drift can be compensated for during computation by inserting a frequency drift and using our method to remove it. We remove both drift on a single qubit and independent drifts on all qubits simultaneously. We believe this method will be useful in keeping error rates low on all physical qubits throughout the course of a computation. Our method is O(1) scalable to systems of arbitrary size, providing a path towards controlling the large numbers of qubits needed for a fault-tolerant quantum computer 
J. Kelly, R. Barends, A. G. Fowler, A. Megrant, E. Jeffrey, T. C.   White, D. Sank, J. Y. Mutus, B. Campbell, Yu Chen, Z. Ch...
quant-ph