Learning noise via dynamical decoupling of entangled qubits
Trevor McCourt, Charles Neill, Kenny Lee, Chris Quintana, Yu Chen, J. Kelly, Jeffrey Marshall, V. N. Smelyanskiy, M. I. Dykman, Alexander N. Korotkov, Isaac L. Chuang, A. Petukhov · Physical Review A · 2023
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 simultaneously 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.