2017/05/31 by Clemens Müller, Jared H Cole, Jared H. Cole +1 · 492 citations
Physics and Astronomy · #Amorphous solid #Electronic circuit #Limit (mathematics) #Niobium #Quantum #Quantum and electron transport phenomena #Quantum tunnelling #Quantum, superfluid, helium dynamics #Superconductivity #Surface and Thin Film Phenomena #cond-mat.mes-hall #quant-ph
paper · pdf · doi:10.1088/1361-6633/ab3a7e
published in Reports on Progress in Physics 82(12), 124501 (IOP Publishing) · 34 pages, 7 figures, 1 table
openalex created_date 2017/05/12 · openalex publication_date 2019/08/12 · arxiv created 2019/10/10 · arxiv updated 2019/10/31 · openalex updated_date 2026/08/05
Amorphous solids show surprisingly universal behaviour at low temperatures. The prevailing wisdom is that this can be explained by the existence of two-state defects within the material. The so-called standard tunneling model has become the established framework to explain these results, yet it still leaves the central question essentially unanswered-what are these two-level defects (TLS)? This question has recently taken on a new urgency with the rise of superconducting circuits in quantum computing, circuit quantum electrodynamics, magnetometry, electrometry and metrology. Superconducting circuits made from aluminium or niobium are fundamentally limited by losses due to TLS within the amorphous oxide layers encasing them. On the other hand, these circuits also provide a novel and effective method for studying the very defects which limit their operation. We can now go beyond ensemble measurements and probe individual defects-observing the quantum nature of their dynamics and studying their formation, their behaviour as a function of applied field, strain, temperature and other properties. This article reviews the plethora of recent experimental results in this area and discusses the various theoretical models which have been used to describe the observations. In doing so, it summarises the current approaches to solving this fundamentally important problem in solid-state physics.