Learning noise via dynamical decoupling of entangled qubits

Understanding noise in entangled systems is a prerequisite for developing scalable quantum computers. Here, we propose and apply multiqubit dynamical decoupling sequences that characterize noise during two-qubit gates. This noise is qualitatively different from the well-studied noise that leads to single-qubit dephasing; it simultane-ously affects the two qubits, inducing fluctuations in their entangling parameter. In our superconducting system, the experimentally observed noise comes from coupler flux fluctuations and is observed to be non-Gaussian, leading to the stepwise decay of signals.

Automated summary

Understanding and characterizing noise during two-qubit gates is crucial for developing scalable quantum computers. In this study, we propose and employ multiqubit dynamical decoupling sequences to capture the noise in entangled systems. The observed noise in our superconducting system is induced by coupler flux fluctuations, which causes fluctuations in the entangling parameter of the two qubits and leads to the stepwise decay of signals.