Finding elusive surface spins on superconducting quantum devices

Findings, recently published in the renowned journal Physical Review Letters, shed new light on the origin of magnetic noise in quantum circuits. "We adress a long standing problem of the source of environment noise in superconducting quantum devices, like squids, q-bits and so on", says Andrey Danilov, Senior Researcher at the Quantum Device Physics Laboratory at MC2, and one of the authors.
​The advancement of quantum computing now faces a tremendous challenge in improving the reproducibility and robustness of quantum circuits. One of the biggest problems in this field is the presence of noise intrinsic to all these devices, which origin has puzzled scientists for many decades.
In the paper "Direct Identification of Dilute Surface Spins on Al2 O3: Origin of Flux Noise in Quantum Circuits" the researchers show that the same signatures of atomic Hydrogen that astronomers use to study the birth of distant stars reveal themselves in very small quantities in these tiny and ultracold quantum circuits.
The identification of the elusive yet detrimental spins mentioned, shed new light on the origin of flux noise in quantum circuits, showing great promise for its mitigation. Remarkably, the highly reactive physisorbed atomic hydrogen, a by-product of water dissociation, was found to be stable in very small densities on the surface of these devices, closely matching the ubiquitous density of previously unknown paramagnetic species inferred to be responsible for flux noise in ultrasensitive SQUID magnetometers.
The presented technique can also be applied to study oxide surface chemistry important for many other fields such as catalysis and gas sensing.
"This is a result of more than two years of work by an international team, with three authors from the Quantum Device Physics lab, and the other four authors formerly affiliated with QDP/Chalmers", says Andrey Danilov.
The involved Chalmers researchers are Andrey Danilov, Astghik Adamyan and Sergey Kubatkin. Collaborating researchers are also Sebastian de Graaf and Tobias Lindström, National Physical Laboratory, UK, Donats Erts, Institute of Chemical Physics, University of Latvia, and Alexander Tzalenchuk, Royal Holloway, University of London.
The paper has been selected as one of the Physical Review Letters Editor's suggestions.
Read the paper >>>

Published: Thu 16 Feb 2017.