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Kim, Heonoh,Lee, Hee Jung,Lee, Sang Min,Moon, Han Seb Optical Society of America 2015 Optics letters Vol.40 No.13
<P>We present a highly efficient source for discrete frequency-entangled photon pairs based on spontaneous parametric down-conversion using 3rd-order type-0 quasi-phase matching in a periodically poled MgO-doped stoichiometric LiTaO3 crystal pumped by a 355.66-nm laser. Correlated two-photon states were generated with automatic conservation of energy and momentum in two given spatial modes. These states have a wide spectral range, even under small variations in crystal temperature, which consequently results in higher discreteness. Frequency entanglement was confirmed by measuring two-photon quantum interference fringes without any spectral filtering. (C) 2015 Optical Society of America</P>
Observation of two-photon interference effect with a single non-photon-number resolving detector
Kim, Heonoh,Lee, Sang Min,Kwon, Osung,Moon, Han Seb Optical Society of America 2017 Optics letters Vol.42 No.13
<P>Multiphoton interference effects can be measured with a single detector when two input photons are temporally well separated when compared with the dead time of the single-photon avalanche detector. Here we experimentally demonstrate that the Hong-Ou-Mandel interference effect can be observed with a single non-photon-number resolving detector via a time-delayed coincidence measurement of successive electrical signals from the detector. The two-photon interference experiment is performed by utilizing temporally well-separated pairwise weak coherent pulses, and the interference fringes are successfully measured with high visibility in the range of the limited upper bound for the weak coherent photon source. (C) 2017 Optical Society of America.</P>
Three-photon N00N states generated by photon subtraction from double photon pairs
Kim, Heonoh,Park, Hee Su,Choi, Sang-Kyung The Optical Society 2009 Optics express Vol.17 No.22
<P>We describe an experimental demonstration of a novel three-photon N00N state generation scheme using a single source of photons based on spontaneous parametric down-conversion (SPDC). The three-photon entangled state is generated when a photon is subtracted from a double pair of photons and detected by a heralding counter. Interference fringes measured with an emulated three-photon detector reveal the three-photon de Broglie wavelength and exhibit visibility > 70% without background subtraction.</P>
Another Quantum Eraser Experiment with Two-photon States of Light
Kim, Tae-Soo,Ko, Jeong-Hoon,Kim, Heonoh Optical Society of Korea 2002 Current Optics and Photonics Vol.6 No.3
The quantum eraser experiment was revisited, using entangled photons of visible light in a Hong-Ou-Handel type interferometer with a magnitude two orders higher than before in count rates. We introduced which-path information by polarization and subsequently erasied this information by means of polarizers in front of detectors. It was found that the visibility of the interference fringe is revived from 0% to 88% as the polarizers are changed from 0$^{\circ}$ to 45$^{\circ}$.
김헌오,신하림,김원식,권오성,김태수,Kim Heonoh,Shin Harim,Kim Wonsik,Kwon Osung,Kim Taesoo 한국광학회 2004 한국광학회지 Vol.15 No.5
매개하향변환과정에서 발생한 640 nm와 660 nm 파장을 갖는 광자쌍의 진동수 얽힘상태를 이용하여 양자간섭실험을 수행하였다. 두 광자의 파장에 대응하는 각진동수가 각각 $\omega$$_1$과 $\omega$$_2$인 광자쌍을 간섭계의 출구에 놓인 두 검출기로 서로 다른 진동수의 광자들을 동시계수할 때, 광의 결맞음 시간이내에서 두 광자가 빔분할기에 도달하는 시간 간격의 변화 $\delta$$\tau$에 따라 동시계수가 변하는 간섭무늬를 관측하였다. We present a quantum interference experiment with frequency-entangled pairs of photons with wavelength of 640 nm and 660 nm produced in the process of parametric down-conversion. When photon pairs in different angular frequencies $\omega$$_1$and $\omega$$_2$are registered by two detectors the coincidence counts exhibits a two-photon fringe as a function of relative time delay $\delta$$\tau$ of two photons within the coherence time depending on the arrangement of the detector pairs.
김재실,배철용,이재환,안대균,최헌오 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
자기베어링의 회전정밀도에 영향을 미치는 인자로 PWM 전력증폭기, 위치 센서 등과 같은 자기베어링 구성 장치의 동특성 및 정밀도, 시스템의 정확한 모델링, 제어기법, 런아웃 등이 있다. 본 연구에서는 능동 자기베어링을 제어하기 위해 자기베어링의 PWM 전력증폭기와 회전축을 모델링하고 이를 바탕으로 능동 자기베어링 제어를 위한 PID제어기를 구성하였으며, 변위 센서의 부착위치 및 회전축의 진원도의 영향으로 발생하는 주기적인 런아웃 요소를 첨가하여 런아웃의 영향을 확인하였으며, 런아웃(Runout)에 의해 발생하는 에러(Error)를 효과적으로 제어하여 자기베어링의 제어 정밀도를 향상시키기 위한 방법으로 기본적인 PID 제어기에 최소평균자승(Least Mean Square, LMS) 알고리즘을 적용한 적응 피드포워드 제어기를 구성하여 자기베어링의 능동 제어에서 발생하는 주기적인 런아웃을 효과적으로 제어할 수 있음을 MATLAB을 통한 시뮬레이션을 통해 확인하였다.
김재실,안승국,이재환,안대균,최헌오 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
This article describes (1) 2 and 3 dimensional electromagnetic finite element models for an active heteropolar radial magnetic bearing, (2) the procedure for obtaining the bearing stiffnesses by simulating the models and (3) the reviews of the models by comparing an experimental test to the ideal closed loop analysis with the stiffnesses calculated from (2). The 3 dimensional model for the magnetic bearing may be very effectively applied to several types of magnetic bearings.