Dynamical Decoupling Protocols for Reconstructing Qubit Charge Noise*

Two-level fluctuators (TLFs) are ubiquitous in quantum devices, but the physical mechanisms behind them are generally unclear. Having an experimentally viable procedure which can identify TLF coupling strengths and switching rates is therefore of considerable interest and could enhance qubit coherence either by improving device design or providing tailored dynamical protection. 

We’ve developed robust protocols for reconstructing the parameters of one or two TLFs. 

Our algorithm relies on a multi-stage approach for control pulse sequence selection, which is designed to adapt to the environment at hand. This allows us to successfully reconstruct a broad spectrum of TLF parameters with no a priori knowledge of the environment at hand, demonstrating significantly higher error tolerance and improved success rates in more challenging multi-TLF environments.