Advances in micro-SQUID design could detect and manipulate single electrons
Advances in micro-SQUID design could detect and manipulate single electrons lead image
SQUIDs — superconducting quantum interference devices — measure magnetic fields and are a useful tool for imaging solid-state surfaces like superconductors. A prototype RF micro-SQUID demonstrated dispersive microwave readout in a scanning SQUID sensor. This advance enables measurements with lower noise for improved spin sensitivity and higher bandwidth in scanning probe measurements.
Researchers have studied parametric amplification and dispersive readout in SQUIDs since the 1980s, but recent developments in nanofabricated superconducting devices have furthered the techniques’ applicability to investigating quantum phenomenon at the mesoscale. This novel micro-SQUID design exploits the Josephson effect to enhance parametric amplification and boost flux sensitivity.
The researchers fabricated their micro-SQUID featuring a Nb/AlOx/Nb trilayer Josephson junction and a superconducting ring designed to carry a critical current of 20 microamps. By combining smaller pickup loops with parametric amplification, they improved their device’s spin sensitivity from hundreds down to only 28.3 µB per root-hertz and their bandwidth to 200 megahertz at 4 Kelvin. Their models show that lower temperatures and higher excitation power could cut flux and spin noise in half at a bandwidth of 20 megahertz. This micro-SQUID holds an advantage over smaller nano-SQUIDs because operating at 4 Kelvin enables its use in a wider range of applications.
The team reports that the improved bandwidth and noise performance could enable other researchers to investigate the topological effects of new quantum information technologies on shorter timescales. “The much-increased bandwidth will potentially enable us to detect dynamics in solid-state systems in real-time,” said Jan-Michael Mol, an author on the paper.
Source: “A micro-SQUID with dispersive readout for magnetic scanning microscopy,” by F. Foroughi, J.-M. Mol, T. Müller, J. R. Kirtley, K. A. Moler, and H. Bluhm, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5030489 .
