Microwave Circuit Analysis of Multi Transmon Qubit System

Abstract

The quest to design a realizable quantum computer is a dream for many for the past few decades. At the moment, one of the promising designs is the transmon qubit, which is a superconducting qubit is the focus of this work. In order to analyze and design different components of a quantum chip, an understanding of the circuitry is required. By varying the circuit parameters, one can design the system according to requirements by constructing the required physical geometry that incorporates the design parameters. In this thesis work, part of the focus was to understand the transmon qubit circuit parameters, extract the circuit parameters such as capacitances from a physical geometry, build analytic and numerical 3D FEM models. Using a circuit model of the qubit system, the interdependence of the resonators that connects qubits with each other can be studied. Their resonances play a role in the qubit Hamiltonian and can be estimated by constructing accurate simulation models. This problem statement has been dealt with in the thesis work by constructing a hybrid circuitry of standard circuit components and 3D FEM simulated qubit unit cells. The quality factor of the measurement readout resonator of a qubit system needs to be characterized in a qubit system in order to target the rate and resolution at which the measurements can be done. In order to do so, the circuit parameters that affect the quality factor needs to be investigated. This problem statement has also been treated in this work.