Abstract
The project uses QuTiP, a quantum computing framework, to simulate interactions between
two-qubits coupled with each other via three resonators. The main aim of this project is to
build a machinery of techniques to understand complex qubit-cavity interactions using QuTiP’s
functionalities. The system simulated mimics the one constructed by McKay et. al. (M15)
and the results of the simulations closely agree with M15’s experimental results. The effect of the
coupling strength between the qubits and the cavities is studied. It was observed that stronger
couplings generated larger separations between the eigen-modes. Studies involving resonance
were used to construct the iSWAP gate, a universal quantum logic gate. This study showed the
importance of external thermal losses due to cavity dissipation, and qubit decay and dephasing.
The Landau-Zener model was tested for the case of multiple crossing; the model motivated the
comparison of three scenarios where the 2 qubits were coupled via: 1 cavity, 3 cavities, and 6
cavities. The study concluded that having multiple modes, which is a consequence of having
multiple cavities, is advantageous for transferring energy from the qubit to the cavity. Finally,
the ac-Stark shift was measured in the system and it’s dynamics showed excellent agreement
with the experimental results obtained by M15.
This project was done as part of the Helen Edwards Summer Internship Program,
Applied Physics and Superconducting Technology Division, Fermilab
July-August 2019
The results of the project are published here.