Mechanically induced correlated errors on superconducting qubits with relaxation times exceeding 0.4 milliseconds*

Superconducting qubits are among the most advanced candidates for achieving fault-tolerant quantum computing. Despite recent significant advancements in the qubit lifetimes, the origin of the loss mechanism for state-of-the-art qubits is still subject to investigation. Furthermore, the successful implementation of quantum error correction requires negligible correlated errors between qubits. Here, we realize superconducting transmon qubits with lifetimes exceeding 0.4 ms using niobium capacitor electrodes shunted by a single Al/AlOx/Al Josephson junction on a silicon substrate and investigate their dominant error mechanism. By introducing a novel time-resolved error detection scheme synchronized with the operation of the pulse tube cooler in a dilution refrigerator, we find that mechanical shocks from the pulse tube induce nonequilibrium dynamics in highly coherent qubits, leading to strongly correlated bit-flip errors. Our observations are consistent with qubit dynamics induced by two-level systems and quasiparticles, thereby deepening our understanding of the qubit error mechanisms. Additionally, our findings provide valuable insights into potential error-mitigation strategies for achieving fault tolerance by decoupling superconducting qubits from their mechanical environments.