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Quantum metrology with single spins in diamond under ambient conditions

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National Science Review 2018年第3期5卷 346-355页

作者： Ming Chen Chao Meng Qi Zhang Changkui Duan Fazhan Shi Jiangfeng Du Key Laboratory of Microscale magnetic resonance and department of Modern Physics University of Science and Technology of China

The detection of single quantum systems can reveal information that would be averaged out in traditional techniques based on ensemble measurements. The nitrogen-vacancy(NV) centers in diamond have shown brilliant prospects of performance as quantum bits and atomic sensors under ambient conditions, such as ultra-long coherence time, high fidelity control and readout of the spin state. In particular, the sensitivity of the NV center spin levels to external environmental changes makes it a versatile detector capable of measuring various physical quantities, such as temperature, strain, electric fields and magnetic fields. In this paper, we review recent progress in NV-based quantum metrology, and speculate on its future.

关键词： diamond nitrogen-vacancy centers quantum metrology quantum sensing quantum information process

Entanglement of a two-qubit anisotropic Heisenberg X Y Z chain in nonuniform magnetic fields with intrinsic decoherence

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Chinese Physics B 2008年第2期17卷 456-461页

作者：徐晓波刘金明于鹏飞 Key Laboratory of Optical and magnetic resonance Spectroscopy Department of PhysicsEast China Normal University

Taking the intrinsic decoherence effect into account, this paper investigates the entanglement of a two-qubit anisotropic Heisenberg XYZ model in the presence of nonuniform external magnetic fields by employing the concurrence as entanglement measure. It is found that both the intrinsic decoherence and the anisotropy of the system give a significant suppression to the entanglement. Moreover it finds that the initial state of the system plays an important role in the time evolution of the entanglement, which means that the entanglement of the system is independent of the nonuniformity and uniformity of the magnetic field when the system is in the initial state ｜ψ （0）） = ｜00） and [ψ′ （0）） = m ｜01）＋ n ｜10）, respectively.

关键词： Heisenberg XYZ chain concurrence magnetic field intrinsic decoherence

Fast high-resolution nuclear magnetic resonance spectroscopy through indirect zero-quantum coherence detection in inhomogeneous fields

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Chinese Physics B 2014年第6期23卷 158-164页

作者：柯汉平陈浩林雁勤韦芝良蔡淑惠张志勇陈忠 department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance Xiamen University

In many cases, high-resolution nuclear magnetic resonance （NMR） spectra are virtually impossible to obtain by con- ventional nuclear magnetic resonance methods because of inhomogeneity of magnetic field and inherent heterogeneity of sample. Although conventional intramolecular zero-quantum coherence （ZQC） can be used to obtain high-resolution spectrum in inhomogeneous field, the acquisition takes rather long time. In this paper, a spatially encoded intramolecular ZQC technique is proposed to fast acquire high-resolution NMR spectrum in inhomogeneous field. For the first time, the gradient-driven decoding technique is employed to selectively acquire intramolecular ZQC signals. Theoretical analyses and experimental observations demonstrate that high-resolution NMR spectral information can be retrieved within several scans even when the field inhomogeneity is severe enough to erase most spectral information. This work provides a new way to enhance the acquisition efficiency of high-resolution intramolecular ZQC spectroscopy in inhomogeneous fields.

关键词： nuclear magnetic resonance intramolecular zero-quantum coherence inhomogeneous magneticfields spatial encoding

High frequency forcing on nonlinear systems

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Chinese Physics B 2013年第3期22卷 209-218页

作者：姚成贵何志威占萌 department of Mathematics Shaoxing University Wuhan Center for magnetic resonance State Key Laboratory of Magnetic Resonance and Atomic and Molecular PhysicsWuhan Institute of Physics and MathematicsChinese Academy of Sciences University of the Chinese Academy of Sciences

High-frequency signals are pervasive in many science and engineering *** this work,the effect of high-frequency driving on general nonlinear systems is investigated,and an effective equation for slow motion is derived by extending the inertial approximation for the direct separation of fast and slow *** on this theory,a high-frequency force can induce various phase transitions of a system by changing its amplitude and *** simulations on several nonlinear oscillator systems show a very good agreement with the theoretic *** findings may shed light on our understanding of the dynamics of nonlinear systems subject to a periodic force.

关键词： high frequency nonlinear oscillator inertial approximation phase transitions

magnetic focusing of cold atomic beam with a 2D array of current-carrying wires

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Chinese Optics Letters 2006年第9期4卷 497-500页

作者：刘泱恽旻印建平 Key Laboratory for Optical and magnetic resonance Spectroscopy department of Physics East China Normal University Key Laboratory for Optical and magnetic resonance Spectroscopy department of Physics East China Normal University

A new scheme to realize a two-dimensional （2D） array of magnetic micro-lenses for a cold atomic beam. formed by an array of square current-carrying wires, is proposed. We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms, and study the dynamic focusing processes of cold atoms passing through the mag- netic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method. The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam, even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.

关键词： magnetic focusing of cold atomic beam with a 2D array of current-carrying wires

Quantum key distribution in 50-km optic fibers

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Science China(Physics,Mechanics & Astronomy) 2004年第2期47卷 182-188页

作者： ZHOU Chunyuan WU Guang CHEN Xiuliang LI Hexiang ZENG Heping Key Laboratory of Optical and magnetic resonance Spectroscopy and Department of Physics East China Normal University Shanghai 200062 China Key Laboratory of Optical and Magnetic Resonance Spectroscopy and Department of Physics East China Normal University Shanghai 200062 China Key Laboratory of Optical and Magnetic Resonance Spectroscopy and Department of Physics East China Normal University Shanghai 200062 China Key Laboratory of Optical and Magnetic Resonance Spectroscopy and Department of Physics East China Normal University Shanghai 200062 China Key Laboratory of Optical and Magnetic Resonance Spectroscopy and Department of Physics East China Normal University Shanghai 200062 China

In this paper, we report our recent experiment of long-distance fiber-optic plug and play quantum cryptography system wherein a Faraday-Mirror was used to compensate for the polarization mode dispersion and phase drifts. The pulse-biased coincident gate single-photon detection technique was used to effectively reduce the noises from the detrimental Rayleigh backscattering. We have achieved a quantum key distribution system with the working distance of 50 km, which was tested to be stable in more than 6 hours continuous work. And we also demonstrated the practical quantum communication in a local area network using the TCP protocol.

关键词： quantum cryptography, single-photon interference, polarization mode dispersion, phase- modula.

Apparent diffusion behaviour of intermolecular double-quantum coherence modulated by a distant dipolar field in solution NMR

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Chinese Physics B 2009年第11期18卷 4797-4806页

作者：沈桂平蔡聪波蔡淑惠陈忠 department of Physics Fujian Key Laboratory of Plasma and Magnetic ResonanceXiamen University department of Communications Engineering Xiamen University

A modified correlated spectroscopy （COSY） revamped with asymmetric Z-gradient echo detection sequence was designed to investigate the influence of diffusion hehaviour on intermolecular double-quantum coherence signal attenuation during the pre-acquisition period. Theoretical formulas were deduced and experimental measurements and simulations were performed. It is found that the diffusion behaviour of intermolecular double-quantum coherence in the pre-acquisition period may be different from that of conventional single-quantum coherence, depending on the relative orientation of diffusion weighting gradients to coherence selection gradients. When the orientation of the diffusion weighting gradients is parallel or anti-parallel to the orientation of the coherence selection gradients, the diffusion is modulated by the distant dipolar field. This study is helpful for understanding the signal properties in intermolecular double-quantum coherence magnetic resonance imaging.

关键词： nuclear magnetic resonance intermolecular double-quantum coherences distant dipolar field diffusion

Differential study of DCE-MRI parameters in spinal metastatic tumors, brucellar spondylitis and spinal tuberculosis

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Chinese Journal of Cancer Research 2018年第4期30卷 425-431页

作者： Pengfei Qiao Pengfei Zhao Yang Gao Yuzhen Bai Guangming Niu department of magnetic resonance Imaging the Affiliated Hospital of Inner Mongolia Medical University

Objective： In the present study, spinal metastatic tumors, brucellar spondylitis and spinal tuberculosis werequantitatively analyzed using dynamic contrast-enhanced magnetic resonance imaging （DCE-MRI） to assess thevalue of DCE-MRI in the differential diagnosis of these ***： Patients with brucellar spondylitis, spinal tuberculosis or a spinal metastatic tumor （30 cases of each）received conventional MRI and DCE-MRI examination. The volume transfer constant （Ktrans）, rate constant （Kep）,extravascular extracellular volume fraction （Ve） and plasma volume fraction （Vp） of the diseased vertebral bodieswere measured on the perfusion parameter map, and the differences in these parameters between the patients ***： For pathological vertebrae in cases of spinal metastatic tumor, brucellar spondylitis and spinaltuberculosis, respectively, the Ktrans values （median ＋ quartile pitch） were 0.989±0.014, 0.720±0.011 and0.317±0.005 min-1; the Kep values were 2.898±0.055, 1.327±0.017 and 0.748±0.006 min-1; the Ve values were0.339±0.008, 0.542±0.013 and 0.428±0.018; the Vp values were 0.048±0.008, 0.035±0.004 and 0.028±0.009; thecorresponding H values were 50.25 （for Ktrans）, 52.47 （for Kep）, 48.33 （for Ve） and 46.56 （for Vp）, and all differenceswere statistically significant （two-sided P〈0.05）.Conclusions： The quantitative analysis of DCE-MRI has a certain value in the differential diagnosis of spinalmetastatic tumor, brucellar spondylitis and spinal tuberculosis.

关键词： Differential diagnosis dynamic contrast enhanced MRI spinal tuberculosis spinal metastatic tumor brucellar spondylitis

Weighted total variation using split Bregman fast quantitative susceptibility mapping reconstruction method

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Chinese Physics B 2018年第8期27卷 645-654页

作者： Lin Chen Zhi-Wei Zheng Li-Jun Bao Jin-Sheng Fang Tian-He Yang Shu-Hui Cai Cong-Bo Cai department of Electronic Science Fujian Provincial Key Laboratory of Plasma and Magnetic ResonanceXiamen UniversityXiamen 361005China magnetic resonance Center Zhongshan HospitalMedical College of Xiamen UniversityXiamen 361004China department of Communication Engineering Xiamen UniversityXiamen 361005China

An ill-posed inverse problem in quantitative susceptibility mapping （QSM） is usually solved using a regularization and optimization solver, which is time consuming considering the three-dimensional volume data. However, in clinical diagnosis, it is necessary to reconstruct a susceptibility map efficiently with an appropriate method. Here, a modified QSM reconstruction method called weighted total variation using split Bregman （WTVSB） is proposed. It reconstructs the susceptibility map with fast computational speed and effective artifact suppression by incorporating noise-suppressed data weighting with split Bregman iteration. The noise-suppressed data weighting is determined using the Laplacian of the calculated local field, which can prevent the noise and errors in field maps from spreading into the susceptibility inversion. The split Bregman iteration accelerates the solution of the Ll-regularized reconstruction model by utilizing a preconditioned conjugate gradient solver. In an experiment, the proposed reconstruction method is compared with truncated k-space division （TKD）, morphology enabled dipole inversion （MEDI）, total variation using the split Bregman （TVSB） method for numerical simulation, phantom and in vivo human brain data evaluated by root mean square error and mean structure similarity. Experimental results demonstrate that our proposed method can achieve better balance between accuracy and efficiency of QSM reconstruction than conventional methods, and thus facilitating clinical applications of QSM.

关键词： quantitative susceptibility mapping ill-posed inverse problem noise-suppressed data weighting split Bregman iteration