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Effect of the Variable b-field on the Dynamic of a Central Electron Spin Coupled to an Anti-Ferromagnetic Qubit bath

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World Journal of Condensed Matter Physics 2012年第4期2卷 246-256页

作者： Martin Tchoffo Georges Collince Fouokeng Siaka Massou Ngwa Engelbert Afuoti Issofa Nsangou Lukong Cornelius Fai Alex Ghislain Tchouadeu Jean-Pierre Kenné De- partment of Physics Faculty of Sciences and Technics University of Abomey-Calavi Cotonou Benin Department of Mechanical Engineering Laboratory of Integrated Production Technologies University of Québec Québec Canada Department of Physics Laboratory of Mesoscopic and Multilayer Structures University of Dschang Dschang Cameroon Department of Physics Laboratory of Mesoscopic and Multilayer Structures University of Dschang Dschang Cameroon Department of Thermal Engineering and Energetics Douala University Institute of Technology Douala Cameroun

This present issue is an extension of the work of Y. Xiao-Zhong et al. who investigated the influence of constant external magnetic field on the decoherence of a central electron spin of atom coupled to an anti-ferromagnetic environment. We have shown in this work that the character variability of the field induces oscillations amongst the eigen modes of the environment. This observation is made via the derivation of the transition probability density of state, a manner by which critical parameters (parameters where transition occur) of the system could be obtained as it shows resonance peak. We equally observed that the two different magnons modes resulting from the frequency splitting via the application of the time-varying external b-field, exhibit each a resonant peak of similar amplitude at different temperature ranges. This additional information shows that the probability for the central spin system to remain in its initially prepared diabatic state is enhanced for some temperature ranges for the corresponding two magnon modes. Hence, these temperature ranges where the probability density is maximum could save as decoherence free environment;an important requirement for the implementation of quantum computation and information processing in solid state circuitry. The theoretical and numerical results presented for the decoherence time and the probability density are that of a decohered central electron spin coupled to an anti-ferromagnetic spin bath. The theory is based on a spin wave approximation and on the density matrix using both transformations of bloch, Primakov and bogoliobuv in the adiabatic limit.

关键词： Decoherence Spin Wave Anti-Ferromagnetic Environment Central Spin Variable b-field

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Formation of RF Plasma Transport Channel in External b-field

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Journal of Energy and Power Engineering 2012年第5期6卷 725-729页

作者： Ping Feng Vitaly bystritskii Ivan Isakov Vasily Matvienko Kurt Walters Department of Physics & Astronomy University of California Irvine California 92697 USA Tri Alpha Energy lnc Foothill Ranch California 92610 USA Institute of High Voltage Technology Tomsk 63050 Russia Institute of Nuclear Physics Tomsk 63050 Russia

The paper describes experiments on formation of a plasma channel with imbedded b-field for transporting high power ion beam. The plasma was generated with a 5-turn loop inductive antenna driven by an H-bridge type RF generator. The azimuthal b-field in the channel of 0.5-1.5 kG was formed by a pulsed current from external capacitor bank. Control of the hydrogen gas pressure was provided by an electromagnetic puffvalve. The paper describes experimental devices and results on the generated plasma parameters as function of RF frequency, antenna voltage, pulse duration and puffgas pressure. When operating at-1 kG b-field, ambient gas pressure in the range of few -10 mTorr, and 5 kV antenna voltage at resonant frequency of 150 kHz, the plasma density range was （3-7）×10^12 cm3 with a temperature of a few eV.

关键词： Plasma RF b-field ion beam high power ion beam.

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Application of TEM based on HTS SQUID Magnetometer in Deep Geological Structure Exploration in the baiyun Gold Deposit,NE China

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Journal of Earth Science 2021年第1期32卷 1-7页

作者： Junjie Wu Xiaodong Chen Yi Yang Qingquan Zhi Xingchun Wang Jie Zhang Xiaohong Deng Yi Zhao Yue Huang Institute of Geophysical and Geochemical Exploration Chinese Academy of Geological SciencesLangfang 065000China Laboratory of Geophysical Electromagnetic Probing Technologies Ministry of Land and ResourcesLangfang 065000China School of Geology Engineering and Geomatics Chang'an UniversityXi'an 710000China

Exploration of deep mineralization,particularly where the mineralization of interest is covered by a conductive overburden,is still a challenge for the conventional transient electromagnetic(TEM)method,which measures TEM response using induction coils as the ***,sensors such as fluxgate and superconductive quantum interfere device(SQUID)magnetometers can measure the b-field directly,which can provide more reliable deep information for mineralization *** this paper,we report on the research and development of our newly developed high-temperature su-perconductor(HTS)SQUID magnetometer,which is cooled by liquid nitrogen at 77 K,and its applica-tion in TEM measurement for deep exploration in a gold deposit in *** improved SQUID magnetometer version has a good performance with noise(60 fT/√Hz),slew rate(0.8 mT/S),dynamic range(100 db),sensitivity(6.25 mV/nT),and bandwidth(DC-20 kHz).To find deep and peripheral ore in the baiyun gold deposit located in Liaoning Province,NE China,both the SQUID magnetometer and induction coil were used for TEM data *** show that TEM can detect the distribution of local strata and the faults contained within *** also indicate that the SQUID magnetome-ter has superior response performance for response over geological targets with slower decay time when compared to the induction coil *** SQUID magnetometer is more sensitive at observing the induced-polarization effect which is closely related to the ore-controlling faults.

关键词： TEM HTS SQUID magnetometer b-field deep exploration the baiyun gold deposit

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Thermodynamic Properties and Decoherence of a Central Electron Spin of Atom Coupled to an Anti-Ferromagnetic Spin bath

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Journal of Quantum Information Science 2013年第1期3卷 10-15页

作者： Martin Tchoffo Georges Collince Fouokeng Lukong Cornelius Fai Mathurin Esouague Ateuafack Mesoscopic and Multilayer Structures Laboratory Department of Physics Faculty of Science University of Dschang Dschang Cameroon

The decoherence of a central electron spin of an atom coupled to an anti-ferromagnetic spin bath in the presence of a time varying b-field (VbF) is investigated applying the Holstein-Primak off and bloch transformations approaches. The boltzmann entropy and the specific heat capacity at a given temperature are obtained and show the correlation of the coupling of the spin bath and the electron spin of the central atom. At low frequencies the coherence of the coupled system is dominated by the magnetic field intensity. At low VbF intensity, there is decrease in entropy and heat capacity at increase external magnetic field that show the decoherence suppression of the central electron spin atom. The crossing observed in the specific heat capacity corresponds to the critical field point bc of the system which represents the point of transition from the anti-ferromagnetic system to the ferromagnetic one.

关键词： Entropy Specific Heat Capacity Varying b-field Decoherence

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