Analysis of loss and noise in superconducting devices sheds new light on problematic two level systems

Superconducting quantum devices have emerged as a frontrunner in the pursuit of innovative new applications of quantum engineering, most notably quantum computing. This has been recognised within the UK with the recent EPSRC funding for founding quantum hubs; of which both the UCL led ‘Quantum Engineering with Solid-state Technologies’ (QUES²T) and Royal Holloway – NPL collaboration on ‘Superconducting Quantum Technology’ (SuQT) focus on the use of superconducting devices for quantum applications.

In recent years it has become increasingly apparent that one of the main problems facing superconducting quantum devices is the comparatively high levels of decoherence which arise as a direct result of the existence of parasitic microscopic two-level systems. These two level systems are situated within the dielectric environment of the superconducting device and are excited by microwave photons in the same range of frequencies that superconducting qubits are operated at. The nature of these two level systems and how to mitigate their effects is the focus of a special issue of IOP Superconductor Science and Technology, entitled ‘Focus on materials for high coherence quantum circuits.’

Within this special issue, UCLQ scientist Jonathan Burnett, in collaboration with Lara Faoro (Rutgers University, USA ) and Tobias Lindstrom (NPL) have published a paper entitled “Analysis of high quality superconducting resonators: consequences for TLS properties in amorphous oxides.” This paper uses superconducting resonators as a testbed to understand two level systems, which produce a temperature and microwave drive dependent loss (quality factor) and 1/f noise level. By carefully studying the loss and noise of difference superconducting resonators for a wide range of temperatures and microwave drives the work has shed new light on the properties of these problematic two level systems. This information is important for learning how to produce quantum devices which are insensitive to the effects of these two level systems.

The precursor for this work was previously published in Nature Communications and was recently awarded the NPL Rayleigh award for 2015. The award recognises scientific excellence and work of high impact from scientists at NPL.

Journal link: Analysis of high quality superconducting resonators: consequences for TLS properties in amorphous oxides IOP SUST, volume 29, 4 (2016)

This paper has been made open access thanks to funding from the UCL Library in a pilot scheme with the IOP.