Two-qubit spectroscopy of spatiotemporally correlated noise in superconducting qubits. Part 2: experiment*

Fault-tolerant quantum computing relies on quantum error correction techniques. Most of these correction schemes assume the noise causing errors to exhibit only weak, spatially decaying correlations between distinct qubits. To investigate these assumptions experimentally, there is a need to extend established noise spectroscopy techniques from single- to multi-qubits systems. In this work, we present experiments on correlated dephasing of two superconducting qubits due to photon shot noise in a shared microwave cavity. Utilizing both free and driven evolution protocols, we demonstrate a frequency-selective method to probe the two-qubit correlations, and show how quantum noise spectroscopy techniques can reconstruct both single-qubit and two-qubit cross-spectra.