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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.
Oscillation of Critical Current by Gate Voltage in Cooper Pair Transistor
송운,정연욱,김남,Song, W.,Chong, Y.,Kim, N. The Korean Superconductivity Society 2010 Progress in superconductivity Vol.11 No.2
We measured the critical current of a Cooper pair transistor consisting of two Josephson junctions and a gate electrode. The Cooper pair transistors were fabricated by using electron-beam lithography and double-angle evaporation technique. The Gate voltage dependence of critical current was measured by observing voltage jumps at various gate voltages while sweeping bias current. The observed oscillation was 2e-periodic, which shows the Cooper pair transistor had low level of quasiparticle poisoning.
10의 -10승 수준에서 조셉슨 전압표준기 불확도 평가
김규태,김문석,정연욱,김완섭,송운,Kim, K.T.,Kim, M.S.,Chong, Y.,Kim, W.S.,Song, W. The Korean Superconductivity Society 2007 Progress in superconductivity Vol.9 No.1
The most recent improvement in the 10 V array system was carried out with focusing on noise reduction. We have evaluated the uncertainty of the 10 V Josephson array system after the improvement. The uncertainty evaluation of 10 V standard included a comparison with a programmable Josephson array system at 1 V. Every contribution to the measurement uncertainty was evaluated in the level of $10^{-10}$. The estimated combined uncertainty was found to be approximately $10^{-9}$ at 10 V, which was limited only by the indirect verifying method. In the near future, a direct comparison with another 10 V Josephson voltage standard is expected to be carried out to provide more accurate uncertainty evaluation for the KRISS Josephson voltage standard.
Al 식각정지층을 이용한 Nb-based SNS 조셉슨 접합의 제조공정
최정숙,박정환,송운,정연욱,Choi, J.S.,Park, J.H.,Song, W.,Chong, Y. 한국초전도학회 2011 Progress in superconductivity Vol.12 No.2
We report our efforts on the development of Nb-based non-hysteretic Josephson junction fabrication process for quantu device applications. By adopting and modifying the existing Nb-aluminum oxide tunnel junction process, we develop a process for non-hysteretic Josephson junction circuits using metal-silicide as metallic barrier material. We use sputter deposition of Nb and $MoSi_2$, PECVD deposition of silicon oxide as insulator material, and ICP-RIE for metal and oxide etch. The advantage of the metal-silicide barrier in the Nb junction process is that it can be etched in $SF_6$ RIE together with Nb electrode. In order to define a junction area precisely and uniformly, end-point detection for the RIE process is critical. In this paper, we employed thin Al layer for the etch stop, and optimized the etch condition. We have successfully demonstrated that the etch stop properties of the inserted Al layer give a uniform etch profile and a precise thickness control of the base electrode in Nb trilayer junctions.
박정환,최정숙,김정구,류상완,송운,정연욱,Park, J.H.,Rehman, M.,Choi, J.S.,Khim, Z.G.,Ryu, S.W.,Song, W.,Chong, Y. The Korean Superconductivity Society 2010 Progress in superconductivity Vol.11 No.2
We measured electrical shot noise in a metal-insulator-metal tunnel junction, which was made by using electron-beam lithography and double-angle evaporation technique. Since the dependence of the shot noise on bias voltage and temperature is theoretically well known, we can determine the temperature of the junction by measuring the noise as the voltage across the junction is changed. A cryogenic low noise amplifier was used to amplify the noise signal in the frequency range of 600-800 MHz, which enabled fast measurement of noise signal and thus temperature. With further study, this method could be useful for primary thermometry in cryogenic temperatures.
최재원,류시정,박정환,류상완,김정구,송운,정연욱,Rehmana, M.,Choi, J.W.,Ryu, S.J.,Park, J.H.,Ryu, S.W.,Khim, Z.G.,Song, W.,Chong, Y. 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2
We report our development of the fabrication process of sub-micron scale $Al-AlO_x-Al$ tunnel junction by using electron-beam lithography and double-angle shadow evaporation technique. We used double-layer resist to construct a suspended bridge structure, and double-angle electron-beam evaporation to form a sub-micron scale overlapped junction. We adopted an e-beam insensitive resist as a bottom sacrificing layer. Tunnel barrier was formed by oxidation of the bottom aluminum layer between the bottom and top electrode deposition, which was done in a separate load-lock chamber. The junction resistance is designed and controlled to be 50 $\Omega$ to match the impedance of the transmission line. The junctions will be used in the broadband shot noise thermometry experiment, which will serve as a link between the electrical unit and the thermodynamic unit.