Full-Wave Methodology to Compute the Spontaneous Emission Rate of a Transmon Qubit

The spontaneous emission rate (SER) is an important figure of merit for any quantum bit (qubit), as it can play a significant role in the control and decoherence qubit. As result, accurately characterizing SER practical devices step design information processing devices. Here, we specifically focus on experimentally popular platform transmon qubit, which kind superconducting circuit Despite importance understanding these qubits, often determined using approximate models or inferred from measurements fabricated device. To improve accuracy predictions process, better to use full-wave numerical methods that make minimal number approximations description systems. In this work, show how be done with recently developed field-based qubits coupled electromagnetic environment. We validate our model by computing similar those found literature have been well-characterized experimentally. further cross-validate results comparing them simplified lumped element transmission line appropriate.