  In the past two decades, one of the fascinating subjects in quantum physics
has been quantum bits (qubits). Thanks to the superposition principle, the
qubits can perform many calculations simultaneously, which will significantly
increase the speed and capacity of the calculations. The time when a qubit
lives in an excited state is called decoherence time. The decoherence time
varies considerably depending on the qubit type and materials. Today, short
decoherence times are one of the bottlenecks in implementing quantum computers
based on superconducting qubits. In this research, the topology of the transmon
qubit is investigated, and the decoherence time caused by noise, flux, and
critical current noise is calculated by numerical method.
