• Progress in Superconductivity
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• v.4 no.1
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• pp.1-9
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• 2002

Transferring single flux quanta across a Josephson junction at an exactly determined rate has made highly precise voltage measurements possible. Making use of self-shunted Nb-based SINIS junctions, programmable fast-switching DC voltage standards with output voltages of up to 10 V were produced. This development is now extended from fundamental DC measurements to the precise determination of AC voltages with arbitrary waveforms. Integrated RSFQ circuits will help to replace expensive semiconductor devices for frequency control and signal coding. Easy-to-handle AC and inexpensive quantum voltmeters of fundamental accuracy would be of interest to industry. In analogy to the development in the flux regime, metallic nanocircuits comprising small-area tunnel junctions and providing the coherent transport of single electrons might play an important role in quantum current metrology. By precise counting of single charges these circuits allow prototypes of quantum standards for electric current and capacitance to be realised. Replacing single electron devices by single Cooper pair circuits, the charge transfer rates and thus the quantum currents could be significantly increased. Recently, the principles of the gate-controlled transfer of individual Cooper pairs in superconducting A1 devices in different electromagnetic environments were demonstrated. The characteristics of these quantum coherent circuits can be improved by replacing the small aluminum tunnel Junctions by niobium junctions. Due to the higher value of the superconducting energy gap ($\Delta_{Nb}$ ＝ $7\Delta_{Al}$), the characteristic energy and the frequency scales for Nb devices are substantially extended as compared to A1 devices. Although the fabrication of small Nb junctions presents a real challenge, the Nb-based metrological devices will be faster and more accurate in operation. Moreover, the Nb-based Cooper pair electrometer could be coupled to an Nb single Cooper pair qubit which can be beneficial for both, the stability of the qubit and its readout with a large signal-to-noise ratio..

• 한국초전도학회:학술대회논문집
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• v.13
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• pp.10-10
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• 2003

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.411-412
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• 2008

• Electronics and Telecommunications Trends
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• v.35 no.2
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• pp.79-88
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• 2020

Quantum computing is regarded as one of the revolutionary computing technologies, and has attracted considerable attention in various fields, such as finance, chemistry, and medicine. One of the promising candidates to realize fault tolerant quantum computing is quantum dot qubits, due to their expectation of high scalability. In this study, we briefly introduce the international tendencies for quantum dot quantum computing. First, the current status of quantum dot gate operations is summarized. In most systems, over 99% of single qubit gate operation is realized, and controlled-not and controlled-phase gates as 2-qubit entangling gates are demonstrated in quantum dots. Second, several approaches to expand the number of qubits are introduced, such as 1D and 2D arrays and long-range interaction. Finally, the current quantum dot systems are evaluated for conducting quantum computing in terms of their number of qubits and gate accuracies. Quantum dot quantum computing is expected to implement scalable quantum computing. In the noisy intermediate-scale quantum era, quantum computing will expand its applications, enabling upcoming questions such as a fault-tolerant quantum computing architecture and error correction scheme to be addressed.

• Electronics and Telecommunications Trends
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• v.38 no.5
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• pp.34-50
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• 2023

Quantum error correction is a key technology for achieving fault-tolerant quantum computation. Finding the best decoding solution to a single error syndrome pattern counteracting multiple errors is an NP-hard problem. Consequently, error decoding is one of the most expensive processes to protect the information in a logical qubit. Recent research on quantum error decoding has been focused on developing conventional and neural-network-based decoding algorithms to satisfy accuracy, speed, and scalability requirements. Although conventional decoding methods have notably improved accuracy in short codes, they face many challenges regarding speed and scalability in long codes. To overcome such problems, machine learning has been extensively applied to neural-network-based error decoding with meaningful results. Nevertheless, when using neural-network-based decoders alone, the learning cost grows exponentially with the code size. To prevent this problem, hierarchical error decoding has been devised by combining conventional and neural-network-based decoders. In addition, research on quantum error decoding is aimed at reducing the spacetime decoding cost and solving the backlog problem caused by decoding delays when using hardware-implemented decoders in cryogenic environments. We review the latest research trends in decoders for quantum error correction with high accuracy, neural-network-based quantum error decoders with high speed and scalability, and hardware-based quantum error decoders implemented in real qubit operating environments.

• ETRI Journal
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• v.45 no.3
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• pp.462-478
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• 2023

In quantum computing, the use of Pauli frames through software traces of classical computers improves computation efficiency. In previous studies, error correction and Pauli operation tracking have been performed simultaneously using integrated Pauli frames in the physical layer. In such a complex processing structure, the number of simultaneous operations processed in the physical layer exponentially increases as the distance of the surface code encoding logical qubit increases. This study proposes a Pauli frame management architecture partitioned into two layers for a lattice surgery-based surface code and describes its structure and operation rules. To evaluate the effectiveness of our method, we generated a random circuit according to the gate ratios constituting the commonly known quantum circuits and compared the generated circuit with the existing Pauli frame and our method. Simulations show a decrease of about 5% over traditional methods. In the case of experiments that only increase the code distance of the logical qubit, it can be seen that the effect of reducing the physical operation through the logical Pauli frame becomes more important.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.84-87
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• 2006

We suggest a procedure entangling two spin-1/2 particles at distant positions such that they cannot be directly entangled via local interaction. An already entangled pair is used to transfer the entanglement to another pair of particles by way of interaction. This scheme of nonlocal generation of entanglement can be used in the construction of a two-qubit universal gate.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.932-933
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• 2014

최근에는 의료 빅데이터 분야에서 의료기기, 의료전문가로부터 생성 또는 감지되는 사운드 생체신호(심장박동, 호흡, 맥박, 진맥) 데이터의 특징을 디지털 데이터로 추출하여 패턴 데이터로 변환한 후, 이를 빅데이터 분석 플랫폼 기반으로 분석하여 진료, 처방, 예방 등에 유용한 정보를 생성하는 모델 구축 연구가 활성화되고 있다. 본 논문에서는 사운드 생체신호 특징을 디지털 데이터로 추출하여 (주)리아컴즈 NeoQubit 빅데이터 플렛폼을 기반으로 패턴 데이터를 분석하고 예측할 수 있는 모델을 제시한다.

• Journal of Information Processing Systems
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• v.14 no.6
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• pp.1331-1346
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• 2018

Aiming at the problem that the gradient-based edge detection operators are sensitive to the noise, causing the pseudo edges, a triqubit-state measurement-based edge detection algorithm is presented in this paper. Combing the image local and global structure information, the triqubit superposition states are used to represent the pixel features, so as to locate the image edge. Our algorithm consists of three steps. Firstly, the improved partial differential method is used to smooth the defect image. Secondly, the triqubit-state is characterized by three elements of the pixel saliency, edge statistical characteristics and gray scale contrast to achieve the defect image from the gray space to the quantum space mapping. Thirdly, the edge image is outputted according to the quantum measurement, local gradient maximization and neighborhood chain code searching. Compared with other methods, the simulation experiments indicate that our algorithm has less pseudo edges and higher edge detection accuracy.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.10-13
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• 2020

High-quality superconducting coplanar waveguide (SCPW) resonators are crucial for developing superconducting quantum information devices and sensors. We designed quarter-wavelength SCPW resonators and fabricated the SCPW resonators using Nb thin film. The resonant characteristics were measured at T = 4.2 K, revealing the intrinsic quality factor and the coupling quality factor to be Qi = 4,784 and Qc = 17, 980, respectively. Our design and fabrication techniques would be very useful to develop a gate-tunable superconducting qubit based on the semiconductor nanostructures.