Frequency-matched antenna for enhancing coupling between transmon qubit and 3D microwave cavity
D.S. Dubyna1*, Y.H. Jhang1, W.C. Chien1, W. Kuo1
1Department of Physics, National Chung Hsing University, Taichung, Taiwan
* presenting author:Dmytro Dubyna,
In study of cavity quantum electrodynamics (cQED), a qubit is coupled to a 3D cavity via an antenna for large coupling energy. However, typical antenna is a narrow-band element and its radiation efficiency at cavity resonance is usually overlooked. In our research we are trying to fill this gap by implementing an original architecture that would allow to use an antenna, modes of which fall in the frequency range of interest without violating significantly cavity quality factor. The design proposed includes 3D cavity itself and adjusted compartment for placing a magnetic coil, which is also has been used as a sample holder. A small part of the antenna of our transmon qubit is situated in 3D cavity providing a microwave coupling while qubit’s SQUID is situated in the middle of magnetic coil providing tunability of qubit’s Josephson energy. According to simulations with high frequency structural simulator (HFSS) software, an appropriate antenna design could lead to frequency matching of antenna and cavity modes that in turn, as we believe, could improve qubit characteristics by increasing qubit-cavity coupling strength. Thus, the study of cavity-qubit-antenna system could be very promising for further development of cQED.

Keywords: cavity quantum electrodynamics, transmon qubit, antenna