Description:

We present a transmon split-junction qubit which can be controlled by Meissner screening currents, which generate required phase bias. The best detected relaxation time (T1) was of the order of 50 μs and the dephasing time (T2) about 40 μs. Meissner qubit allows a strong mixing of the current flowing in the qubit junctions and the currents generated by Abrikosov vortices. We present a quantitative analysis of the radiation-free relaxation in qubits coupled to the vortices. The observation of coherent quantum oscillations provides evidence that the position of the vortex as well as its velocity do not have to accept exact values, but can be smeared in the quantum mechanical uncertainty. The eventual relaxation of such states contributes to an increased relaxation rate of the qubit coupled to the vortices. Such relaxation is described using basic notions of the Caldeira-Leggett quantum dissipation theory. If time permits, we will consider other types of devices, such as superconducting memory elements and superconducting diodes, also controlled by the Meissner current phase shifts.

Alexey Bezryadin, Professor, University of Illinois - Urbana/Champaign

Host: Venkat Chandrasekhar