Recent research trends for high coherence quantum circuits
Recent developments towards improving coherence times are discussed. Dial and co-researchers measure a series of such qubits designed to have varying sensitivities to different surface loss sources. While the results cannot conclusively pinpoint which type of surface loss dominates, it was found that substrate loss even for sapphire can limit coherence times. It is also pointed out that due to the large variations of coherence times across wafers, there is a need to build up sufficient statistical data to reach appropriate conclusions. Burnett et al, present a model for the TLS (two-level system) loss where the interaction between coherent and incoherent TLS plays a more significant role. In the paper by Richardson and colleagues present a detailed study of the growth and patterning of high quality resonators is presented. The resonators are made from MBE grown aluminum on two substrates, silicon and sapphire, both known for their low dielectric losses. Tuckerman and colleagues report on a new transmission line interconnect physical platform, based on niobium microstrip structures with polyimide (PI-2611 and HD-4100) dielectrics, which promises high wire density, wide bandwidth, low heat leakage, and mechanical compliance.