Toward All-in-One Electrical Standards With the Quantum Anomalous Hall Effect

The Technology

To perform critical tasks such as safely navigating planes and precisely fabricating billions of microchips, the U.S. military and industry must calibrate their power supplies and electrical measuring devices using the most up-to-date quantum standards for voltage and resistance. However, those calibrations are costly and time-consuming, requiring engineers to send their electronic devices to the National Institute of Standards and Technology (NIST) for four to six weeks. Adding to the expense, the calibrations involve multiple steps because the electrical standards for voltage and resistance are created in different instruments. This also reduces accuracy.

NIST scientists are now studying a class of quantum materials that could allow voltage and resistance standards to be realized in the same device. With the help of collaborators and investors to broaden and accelerate the project, the study may ultimately lead to the design of a portable, all-in-one system for realizing voltage, resistance and current standards, fundamentally changing the way electrical measurements are calibrated in industry, military and research settings.

Advantages Over Existing Methods

If such a design can be realized, companies would have an opportunity to perfect, manufacture and distribute the system, enabling numerous stakeholders to save both money and time by recreating the electrical standards in their own laboratories instead of sending their devices to NIST.

At present, both voltage and resistance standards are tied to the International System of Units (SI) through different, mutually exclusive quantum effects. On the one hand, the voltage standard, based on the behavior of superconducting material, can only be created in the absence of a magnetic field. On the other hand, the resistance standard, based on the quantum Hall effect, requires a magnetic field more than 100,000 times stronger than that of Earth.

Recently, however, scientists demonstrated that a different quantum phenomenon, known as the quantum anomalous Hall effect (QAHE), can generate an SI resistance standard in a special class of ultrathin materials without the need for a magnetic field. The only obstacle has been that most of the materials, known as magnetic topological insulators, must be cooled to less than two-hundredths of a degree above absolute zero, requiring a costly and bulky dilution refrigerator that would not be portable.

Applications

New advances in material research indicate that some ultrathin topological materials exhibit QAHE at temperatures high enough that a portable refrigeration system would suffice, potentially enabling voltage and resistance standards to be created in a single, portable cryostat. Using a simple physics equation known as Ohm’s law, a standard for electric current can be realized directly from the voltage and resistance standards.

NIST scientists Curt Richter and Paul Haney and their colleagues are now conducting an extensive study of these materials and plan to work with leading U.S. researchers to fabricate an all-in-one electronic calibration system. Collaborating with NIST on the study of promising topological materials could have other payoffs. It may lead to the discovery of new physical processes, some of which might play a role in building error-resistant quantum computers.

Although the compact system would be too large to fit on a chip, its design would make it accessible to individual researchers, industry and the military. In this way, the system would meet the criteria of the NIST on a Chip mission.