Temperature Dependence of Pure Dephasing for a 2D Tantalum Transmon Qubit

Abstract

Over the past two decades, quantum computing has shown great promise for the potential of solving problems at exponentially faster speed-ups compared to classical computers. However, one of the greatest limitations in scaling quantum computers is qubit decoherence, quantified through relaxation T1 and dephasing T2 times. State of the art 2D tantalum-based transmons developed in the Houck lab have shown excellent improvements in relaxation, making dephasing T2 a limiting factor. Multiple dephasing mechanisms have been theorized, however it is not clear how these mechanisms can be extracted from current T2 data. By measuring the qubit dephasing rate at different temperatures, we attempt to identify noise sources based on their temperature dependence. In particular, we will show how, at large temperatures, our transmon is limited by photon shot noise-induced dephasing while at low temperatures 1/f-noise dominates in a linear fashion.