Researchers from the University of Bath have developed a technique for creating single-crystal flake devices so thin and pure that they may be able to outperform existing components for quantum computers.
The researchers made the discovery while exploring the junction between two layers of a superconductor – niobium diselenide – after the layers were cleaved apart, twisted 30° with respect to one another and then stamped back together. This process created a superconducting quantum interferometer device (aka ‘SQUID’): an extremely sensitive sensor used to measure magnetic fields.
SQUIDs, which are based on superconducting loops, are crucial components in MEG imaging and are also used in MRI; cardiography; mineral exploration; scanning microscopes; gravitational wave detection, and in commercial quantum computers.
Although this work remains at an early stage, these new superconducting flakes have the potential to play an important part in the development of quantum computing in coming years.
“Due to their atomically perfect surfaces, which are almost entirely free of defects, we see potential for our crystalline flakes to play a significant role in building quantum computers of the future,” said Professor Simon Bending, an expert in the magnetic properties of superconducting materials at the University of Bath and an author of the Nano Letters report.
“Also, SQUIDs are ideal for studies in biology – for instance, they are now being used to trace the path of magnetically labelled drugs through the intestine – so we’re very excited to see how our devices could be developed in this field, too.
“This is a completely new and unexplored approach to making SQUIDs and a lot of research will still have to be done before these applications become a reality.”
The flakes from which these superconductors are fabricated are extremely thin single crystals that bend easily, making them suitable for incorporation into flexible electronics.
As the bonds between layers of the superconductor are so weak, cleaved flakes – with their completely flat, defect-free surfaces – create atomically sharp interfaces when stamped back together again. This makes them ideal candidates for components of quantum computers.
The physicists were also able to show that the properties of their devices could be systematically tuned by varying the twist angle between the two flakes.
Although this is not the first time niobium diselenide layers have been stamped together to create a weak superconducting link, it is the first demonstration of quantum interference between two such junctions patterned in a pair of twisted flakes. This effect allows the physicists to modulate the maximum current that can flow through the SQUIDs by applying a small magnetic field, creating a highly sensitive field sensor.
