Learning Noise via Dynamical Decoupling of Entangled Qubits

Trevor McCourt | Charles Neill | Kenny Lee | Chris Quintana | Yu Chen |  Jullian Kelly | Vadim Smelyanskiy | Alexander Korotkov | Isaac Chuang | Andre Petukhov

Noise in entangled quantum systems is difficult to characterize due to the many degrees of freedom, and also poses a challenge to quantum computing, where two-qubit gate performance is critical. We develop and apply two-qubit dynamical decoupling sequences to characterize the noise that occurs during two-qubit gates on a superconducting qubit system. The dominant noise observed is consistent with coupler flux noise, which fundamentally affects two qubits at a time and enters through their entangling parameter. This noise is very different from the single-qubit dephasing noise that is typically studied. Additionally, discrete steps are observed in the decoupled signals, implying the presence of non-Gaussian noise that is atypical in solid-state systems.

Funding Sources: MIT