Quantum Leap: How New Technology Could Power Quantum Computing?

Researchers build new technology to advance quantum computers and superconducting electronics

Quantum computing promises huge possibilities for the development of individuals, societies and corporations. From academic practices to big business development, quantum computing is transforming everything. As the technology for building quantum computers is starting to gain momentum, superconductors are becoming more valuable embraced by tech giants such as IBM and Intel. A set of physical properties observed in certain materials, superconductors conduct electricity without resistance when it becomes colder than a critical temperature. They are widely used in medical imaging, electronic devices, magnetic shielding, quantum PCs, etc.

As superconductors provide a macroscopic glimpse into quantum phenomena, they are often expensive to manufacture and prone to err from environmental noise. However, in an effort to change that, researchers from Karl Berggren's group in the Department of Electrical Engineering and Computer Science are developing a superconducting nanowire. It could enable more efficient superconducting electronics. According to Berggren, the nanowire's potential benefits derive from its simplicity.

According to the paper, most metals lose resistance and become superconducting at extremely low temperatures, just a few degrees above absolute zero. They are used to sense magnetic fields, especially in highly-sensitive situations like monitoring brain activity. They also have applications in both quantum and classical computing. Underlying such superconductors is a device invented in the 1960s called the Josephson junction that is fundamentally quite a delicate object. However, it is costly and complex to manufacturing, especially for thin insulators. Josephson junction-based superconductors also may not play well with others, Berggren noted. This lack of ability to control larger-scale objects is a real drawback when trying to interact with the outside world. This is where Berggren's superconducting nanowire plays a crucial role.

In 1956, an electrical engineer at MIT, Dudley Buck published a description of a superconducting computer switch called the cryotron, which was little more than two superconducting wires. One was straight and the other was coiled around it. The cryotron performs as a switch, and when current flows through the coiled wire, its magnetic field lessens the current flowing through the straight wire. Now, researchers from Berggren's group are revitalizing Buck's ideas about superconducting computer switches.

Their superconducting nanowire device, dubbed as nano-cryotron, uses heat to trigger a switch, rather than a magnetic field. Current in this device runs through a superconducting, supercooled wire called the channel. Researchers have already demonstrated proof-of-concept for the nano-cryotron's use as an electronic component. According to Berggren, the superconducting nanowire could one day complement – or perhaps compete with – Josephson junction-based superconducting devices.

Today, many big companies are racing to quantum supremacy that has long been seen as a milestone for quantum computers. In October 2019, Google announced that it had achieved quantum supremacy with a machine that performed a particular calculation. Last year, multinational conglomerate Honeywell announced that it had achieved a breakthrough in quantum computing that expedites the capability of quantum computers.

More broadly, quantum computing is expected to perform complex computations faster and more efficiently than the most powerful supercomputers available today. This significant acceleration could expand the scope of computing, revolutionizing the industry, economy and society.