Improving Qubit Lifetimes With Low Frequency Transmons: From Design to Measurement

Abstract

Large-scale fault-tolerant quantum computers and processors have the potential to significantly impact fields of cryptography, physics simulation, optimization, and more. Superconducting qubits are a leading implementation platform for quantum computers. The 2D transmon is a particular type of superconducting qubit that is widely used due to its charge noise resilience. Still, one of the key challenges in superconducting quantum computing is to improve 2D transmon relaxation (T1) and coherence (T2) times, for which the highest reported values have been shown to be up to 2.5 milliseconds. There is a demonstrated inverse relationship between the the relaxation time (T1) and the qubit operating frequency (ω_q) represented by T1 = Q/ω_q, where qubit quality factor is represented by Q. Recent work on tantalum-on-silicon-based 2D transmons demonstrates a Q = 2.5 × 10^7, attaining a maximum qubit lifetime of 1.6 milliseconds with a qubit frequency of 2.4 GHz. This work investigates the potential of lowering ω_q on tantalum on-silicon-based 2D transmons to increase qubit relaxation times, and provides an overview of the process of design, simulation, fabrication, and measurement required to do so.