Condensed Matter Seminars

Superconducting qubits have emerged as the prominent building block of a scalable quantum computer. While inventing novel qubit designs has enabled the progress towards multiqubit systems that have demonstrated quantum advantage, there much more to be gained by properly engineering the qubit materials. Coherence time of the qubit, the relevant figure of merit, is limited by materials losses. In particular, the main limiting factor is the presence of “parasitic” two-level systems (TLS) that manifest in increased losses of the superconducting circuits at millikelvin temperatures and single-photon powers. Amorphous oxides, residues and transition layers at interfaces and grain boundaries are identified as sites harboring such TLS states. In this talk, I will present techniques to carefully address each interface, superconducting films, and substrate, and ultimately reduce the losses in the superconducting circuit in the quantum regime (millikelvin temperatures, single-photon occupancy). This will ultimately allow to push the envelope regarding coherence times and allow for quantum processors with larger number of qubits and larger quantum volume.