Rhenium as a novel superconducting material for transmon qubits*

Niobium and aluminum have been widely used to realize superconducting qubits. However, the native oxide at the metal air interface limits the qubit lifetime. This layer is highly disordered and it induces losses limiting the performances of the qubits. Recently, tantalum led to great improvement in qubit relaxation time by implementation. This improvement has been attributed to a thinner and less disordered oxide layer compared to Nb and Al. Here, for the first time, we demonstrate a new superconducting material platform: rhenium. Rhenium is more resistant to oxidation; it forms a thin oxide layer that is < 1 nm. We report statistics of T1 relaxation measurements of Re qubits, and compare the results to Nb qubits as well as Re encapsulated Nb qubits. Various transmon designs with varying participation ratios of interfaces and layers are used for these studies.