The Applied Superconductivity Lab in the Department of Electrical and Computer Engineering at Seoul National University, led by Professor Seungyong Hahn, has announced a groundbreaking broadband filter capable of dramatically reducing quantum signal loss in superconducting quantum computers. This achievement was made through collaborative research with the Korea Research Institute of Standards and Science (Director: Yongho Lee). The broadband filter, designed under the leadership of Researcher Seonghyeon Park from the Applied Superconductivity Lab, was fabricated and measured with the assistance of Senior Researcher Gahyun Choi from the Korea Research Institute of Standards and Science.

Superconducting quantum computers utilize qubits made from superconductors to process quantum signals. In the processing of these signals, the issue of quantum signal loss has been a significant engineering challenge. The quantum signal filters proposed previously faced limitations such as large size (~20 mm2), narrow passband width (~200 MHz), and ineffective reduction of losses. These challenges remained obstacles to the development of large-scale quantum computers. Professor Han Seung-yong's research team has successfully developed an ultra-compact quantum signal loss prevention filter with a broadband passband width of 800 MHz, overcoming the previous limitations. The size of the filter is as small as 0.3 mm².

Professor Seungyong Hahn stated in the paper that the ultra-compact filter presented in this study can be applied in various ways to existing superconducting quantum computer systems. He also expressed expectations that by presenting various designs, this research will contribute to the development of scalable and versatile fault-tolerant quantum computing systems. The research findings have been highly praised for their compact design and versatility in the field of applied physics, leading to their selection as Editor’s Pick and publication in the international academic journal Applied Physics Letters.

[Related Paper]

SH Park, G Choi, G Kim, J Jo, B Lee, G Kim, K Park, Y-H Lee, S Hahn, “Characterization of Broadband Purcell Filters with Compact Footprint for Fast Multiplexed Superconducting Qubit Readout,” Applied Physics Letters, vol. 124, no. 4, p. 044003, 2024. [https://doi.org/10.1063/5.0182642]
Figure 1. Implementing existing 10mm² scale filters into a 500 μm x 580 μm (0.29 mm²) filter, proving its broad passband width and effective quantum signal loss reduction: (a) Magnified image of a filter and measuring chip; (b) Verifying broadband passband width of ~800MHz through frequency response(S21, red solid line) of the filter; (c) Qubit signal lifetime is improved as the number of filters(1: greed dashed line, 2: blue solid line) increase

Source:  https://ece.snu.ac.kr/ece/news?md=v&bbsidx=54258

Translated by: Jiyong Yoo, English Editor of the Department of Electrical and Computer Engineering, cyoo7@snu.ac.kr