Superconducting 3D Cavity with Tunable Qubit Energy for Realizing Quantum Electrodynamics
D. S. Dubyna1*, Y. H. Jhang1, W. C. Chien1, Y. L. Hsieh1, W. Kuo1
1Department of Physics, National Chung Hsing University, Taichung, Taiwan
* presenting author:Dmytro Dubyna,
Implementation of tunable qubit energy inside a superconducting 3D cavity is of interest to quantum electrodynamics. For that purpose, an original architecture that includes 3D cavity itself and adjacent compartment for placing a magnetic coil was fabricated of high-purity 5N5 aluminum alloy. Josephson energy of a qubit could be controlled by applying magnetic field to a SQUID loop that is connected to two paddles of asymmetric dipole antenna, the longest of which only partially penetrates inside the cavity providing a microwave coupling. The design proposed allows to use relatively long antennas with the total length up to 23 mm that leads to the falling of antenna fundamental mode in the frequency range of interest. Simulations of cavity-antenna system with high frequency structural simulator (HFSS) software show an increase of cavity-antenna coupling strength from 60 MHz to 447 MHz when penetration length of the antenna inside the cavity increases from 1 mm to 5 mm. Also, HFSS simulations of cavity-antenna-qubit system where a parallel LC circuit mimics a qubit were done. An increase of cavity-qubit coupling strength from 63 MHz to 72 MHz with a growth of cavity-antenna detuning from 0.3 GHz to 1.8 GHz for penetration length of antenna inside the cavity equal to 1 mm demonstrates an insignificant impact of antenna length on the cavity-qubit coupling.

Keywords: quantum electrodynamics, qubit, 3D cavity