Microwave absorbing material using 'graphene' with low heat capacity
Rapid measurement of electrical resistance using 'Josephson junction structure'
Expected to be utilized in next-generation quantum information technology
A team led by Professor Lee Gil-ho of the Department of Physics at POSTECH, in collaboration with Harvard University, the Massachusetts Institute of Technology, and Raytheon BBN, measured microwave intensity at the theoretical limit of 1 attowatt (aW) per second. It was announced on the 4th that an ultra-high sensitivity detector capable of detecting at the level of 1 aW (100 quadrillionths of a W) has been developed.

Recently, as it has become known that microwaves can be utilized in quantum information technologies such as quantum computing and quantum information communication, research aimed at detecting them with ultra-high sensitivity is actively underway.
Bolometers currently used as microwave detectors consist of a microwave-absorbing material, a material that converts absorbed microwaves into heat, and a material that converts the generated heat into electrical resistance, and they calculate the intensity of the absorbed microwaves using changes in electrical resistance.

However, because bolometers use semiconductor devices such as silicon or gallium arsenide as microwave absorption materials, precise intensity measurement was impossible, with the detection limit remaining at the level of 1 nanowatt (nW, 1 nm is 1/1,000,000,000 W) per second of measurement.

Professor Lee's team increased microwave absorption rates by using graphene instead of commercially available semiconductors. Furthermore, by introducing a 'Josephson junction structure' that sandwiches graphene between two superconductors, they reduced the change in electrical resistance generated by graphene to 10 picoseconds (ps. 1 ps made it possible to detect within 1/100 billionth of a second.

As a result, the microwave detection was able to be increased to the theoretical limit of 1 attowatt (aW) per second.

"It is significant that we have established foundational technology for the actual implementation of next-generation quantum devices," said Professor Lee. "By utilizing this technology, we can maximize the measurement efficiency of quantum computing and enable the development of large-scale quantum computers."