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Chong, Yonuk The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.4
Quantum information processing using superconducting qubit based on Josephson junction has become one of the most promising candidates for possible realization of a quantum computer. In the heart of the qubit circuits, the superconducting microwave resonator plays a key role in quantum operations and measurements, which enables single-photon level microwave quantum optics. During last decade, the coherence time, or the lifetime of the quantum state, of the superconducting qubit has been dramatically improved. Among several technological innovations, the improvement of superconducting microwave resonator's quality has been the main driving force in getting the qubit performance almost ready for elementary quantum computing architecture. In this paper, I will briefly review very recent progresses of the superconducting microwave resonators especially aimed for quantum device applications during the last decade. The progresses have been driven by ingenious circuit design, material improvement, and new measurement techniques. Even a rather radical idea of three-dimensional large resonators have been successfully implemented in a qubit circuit. All those efforts contributed to our understanding of the qubit decoherence mechanism and as a result to the improvement of qubit performance.
A brief review on the recent progress of superconducting nanowire single photon detectors
Chong, Yonuk The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.4
Superconducting nanowire single photon detectors (SNSPD) have become the most competent photon-counting devices in wide range of wavelengths. Especially in the communication wavelength (infrared), SNSPD has shown unbeatable superior performance compared to the state-of-art semiconductor single photon detectors. The technology has matured enough for the last decade so that several commercial systems are now almost ready for routine use in general optics experiments. Here we summarize briefly the recent progress in this research field, and hope to motivate further research on the improvement of the device and the system. We cover the basic key concepts, device and system performances, remaining issues and possible further research directions of SNSPD.
Enhancement of heat exchange using On-chip engineered heat sinks
Chong, Yonuk The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.4
We report a method for improving heat exchange between cryo-cooled large-power-dissipation devices and liquid cryogen. Micro-machined monolithic heat sinks were fabricated on a high integration density superconducting Josephson device, and studied for their effect on cooling the device. The monolithic heat sink showed a significant enhancement of cooling capability, which markedly improved the device operation under large dc- and microwave power dissipation. The detailed mechanism of the enhancement still needs further modeling and experiments in order to optimize the design of the heat sink.
정연욱(Chong, Yonuk) 대한전기학회 2022 전기의 세계 Vol.71 No.12
다양한 분야의 기술이 고도화되면서 양자역학을 실제 활용할 수 있는 양자기술이 21세기 들어와 비약적으로 발전하고 있다. 특히 정보처리분야에서 관심이 높으며, 이러한 분야를 양자정보기술이라고 한다. 본고에서는 양자정보기술의 핵심인 양자컴퓨터의 현황과 발전동향을 살펴보기로 한다. Recent progress in high technology enabled utilizing the quantum effects in the possible practical applications. The quantum technology had a great leap in 21st century. The quantum information processing is particularly of interest. In this manuscript I will review the current status of the quantum information technology, especially the quantum computers and its technology development.
Superconducting Junction of a Single-Crystalline Au Nanowire for an Ideal Josephson Device
Jung, Minkyung,Noh, Hyunho,Doh, Yong-Joo,Song, Woon,Chong, Yonuk,Choi, Mahn-Soo,Yoo, Youngdong,Seo, Kwanyong,Kim, Nam,Woo, Byung-Chill,Kim, Bongsoo,Kim, Jinhee American Chemical Society 2011 ACS NANO Vol.5 No.3
<P>We report on the fabrication and measurements of a superconducting junction of a single-crystalline Au nanowire, connected to Al electrodes. The current−voltage characteristic curve shows a clear supercurrent branch below the superconducting transition temperature of Al and quantized voltage plateaus on application of microwave radiation, as expected from Josephson relations. Highly transparent (0.95) contacts very close to an ideal limit of 1 are formed at the interface between the normal metal (Au) and the superconductor (Al). The very high transparency is ascribed to the single crystallinity of a Au nanowire and the formation of an oxide-free contact between Au and Al. The subgap structures of the differential conductance are well explained by coherent multiple Andreev reflections (MAR), the hallmark of mesoscopic Josephson junctions. These observations demonstrate that single crystalline Au nanowires can be employed to develop novel quantum devices utilizing coherent electrical transport.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-3/nn1035679/production/images/medium/nn-2010-035679_0005.gif'></P>