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

TL;DR

This paper introduces a full-wave numerical methodology to accurately compute the spontaneous emission rate of transmon qubits, improving upon approximate models and validated against experimental data and simplified circuit models.

Contribution

It presents a novel full-wave field-based approach for predicting transmon qubit SER, enhancing accuracy over traditional approximate methods.

Findings

Validated the model with experimentally characterized devices

Compared results with lumped element and transmission line models

Demonstrated improved prediction accuracy for SER

Abstract

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