AQP Seminar: Intrinsically protected superconducting qubits: from concepts to realization

Aalto Quantum Physics -seminaari (Micronova). Puhuja: Prof. Jens Koch (Northwestern University)

The transmon qubit owes its remarkable success to its robust protection from the detrimental effects of 1/f charge noise, and to its relative simplicity as one of the smallest anharmonic superconducting circuits. However, the transmon remains fully sensitive to depolarization processes, making T1 limitations an ongoing challenge.

Several proposals exist for achieving universal protection from both depolarization and dephasing in superconducting qubits - among them the 0-pi qubit and the current-mirror qubit. In this talk, I will present the overarching concepts of disjoint-support wavefunctions and robust ground state degeneracy, and illustrate how they emerge in concrete circuits. Following a discussion of spectra and coherence-times estimates for the 0-π qubit, I will address some of the new challenges associated with simulating and operating protected qubits. Finally, I will give an outlook on brand-new data on the first experimental realization of the 0-π qubit in the Houck lab.