Capacitive Coupling of Coherent Quantum Phase Slip Qubits to a Resonator*

A Coherent quantum phase slip (CQPS) is the tunneling of quantised fluxes across a nanowire in a superconducting loop (accompanied by a phase jump 2π) as a result of the quantum fluctuation of the order parameter. These quantum phase slips [1] are dual to Cooper-pair tunnelling in Josephson junctions (JJ), and were thus proposed as the non-linear element, dual to the JJ, which allows to design a current standard.

In the first and most experimental realisations so far, the CQPS element was formed by narrowing the inductive loop wire, and the qubit was coupled inductively to the transmission line [2]. Here, we demonstrate capacitive coupling of CQPS qubits to a resonator. Since the qubit is galvanically decoupled from the resonator, our approach provides flexibility in material choice, design and fabrication. In addition to exploring the charge-phase duality, our motivation is to enable hybrid structures where the resonator is fabricated out of a different material to the phase slip junction. 

[1] J.E. Mooij and Y.V. Nazarov, Nature Physics 2, 169-172 (2006)

[2} O.V. Astafiev, L.B. Iodde, S. Kafanov, Y. A. Pashkin, K. Y. Arutyunov, D. Shahar, O. Cohen, and J. S. Tsai, Nature 484, 355-358 (2012)