Intrinsic coherence of long-lived two-level systems

Characterize the intrinsic coherence of long-lived two-level systems whose lifetimes exceed those of superconducting qubits.

Background

Long-lived two-level systems have been observed in several superconducting-qubit platforms and can retain excitations for much longer than the qubits to which they are coupled. Their interaction with qubits produces non-Markovian dynamics and may create hidden temporal correlations relevant to quantum error correction. While their presence has been established, the degree and mechanisms of their intrinsic coherence remain unresolved, motivating direct measurements of their dephasing and relaxation properties.

References

While the presence of long-lived TLSs has now been established in several platforms, their intrinsic coherence remains an open question.

— Superconducting circuits host two-level systems with lifetimes exceeding one second  (2610.21853 - Féchant et al., 15 Oct 2026) in Section 1, paragraph beginning “Building on these developments”