Coherent Control Of Electron Spin In Diamond

In classical world,overwhelmed by increasing amounts of information,search-ing a efficient method to store and process information is very emergency.Conven-tional silicon-based electronics has experienced rapid and steady development,due to the progressive miniaturization of its basic component,the transistor,but that trend can’t continue indefinitely by semiconductor technology.When the size of transistor decreases to few nanometer,the quantum phenomenon will become a biggest stumbling block.Hence,there’s no choice except for fighting against the quantum limitation or employing quantum laws to enhance the capability of information process.Quantum information process(QIP)is such wise way to handle with above task,which exploit the quantum features of superposition and entanglement.Moreover,it could to be able to transmit data that is fundamentally secure and solve problems that are beyond the power of modern computers.Recently,diamond has emerged as an excellent material system with unique prop-erties for QIP.In particular,thanks to ultra-long coherence time,high fidelity control,biocompatibility and optical readout of the spin level under room-temperature,the elec-tronic spin of nitrogen-vacancy(NV)color centers in diamond make a big breakthrough in quantum computation,quantum simulation and quantum sensing.In this thesis,we locate NV center with confocal microscopy.By combining mi-crowave operation,the quantum coherent control,quantum Deutsch-Jozsa algorithm,quantum sensoring at nanoscale and quantum metrology assistted by entanglement.Be-low,we briefly give a introduction of thses aspects:1.We shown how to locate single NV center in diamond by home-built confocal microscopy with a high signal-to-noise ratio.By investigation the optical polarization dependent charge state conversion(CSC),the related fluorescence anomalous saturation were experimentally studied in details.In the end,by optimizing the laser polarization,fast charge state initialization and high fluorescence intensity of NV center could be obtained under same pumping power.2.The single-qubit operation of NV center was demonstrated experimentally,which is basic content of QIP,could be realize by employing the principle of light-matter interaction.Based on coherent single-qubit operation,we carried out the first quantum algorithm——Deutsch-Jozsa algorithm with NV center.And the results demonstrated that the quantum algorithm would be better than the classical method or fail completely depending on the delay time of the measurement,which was beyond the regime of con-ventional Born-Markovian.We observed memory effect of the environment for single NV center and explaind the results of D-J algorithm by non-Markovian theory.Based on a complete understanding of the non-Markovian environment,we enhanced the fi-delity of the D-J algorithm to above 97%and observed the fine spectrum structure in frequency realm.Moreover,we also demonstrated how to isolate a few procimal nu-clear spin from the rest of the environment and use them as a quantum register.3.By making use of multi-microwave synchronous coherent operation,we en-hanced the sensitivity and extended the application of single NV center in quantum sensoring.Due to coupling with dark spin in diamond,the spectrum of NV center was always split into many structures,which decreases its the performance in quan-tum sensoring.And we carefully dealed with spectrum splitting of NV center with multi-microwave synchronous operation and demonstrated almost 3-fold improvement in signal-to-noise ratio and sensitivity.This experiment represented an important step towards making fully use of NV center’s quantum coherence in realistic quantum sens-ing application.4.In Non-Markovian environment,we recovered the measurement precision with quantum many-body entanglement by dynamic decoupling method.Usually,the uncer-tainty of detection parameter could be reduced to Heisenberg quantum limit(HQL)by quantum entangled probe and yield higher precision result than purely classical method.However,any little amount of noise could totally break down precision of quantum strat-egy to standard quantum limit(SQL).In order to keep the advance of quantum strategy alive,we firstly presented the protected quantum metrology protocol to revive super-classical resolution scales as N-11/12 in the realistic environment,which opened the door of weak signal detection of microcosmic physics by quantum resource.Recently,many studies focused on the quantum feedback control,large scale quan-tum simulation,and hybrid quantum sensoring of NV center.Our works would lay the foundation of them.By exploring the characters of NV center’s the environment,we will realize hgh-fidelity quantum contrcol and make fully use of quantum coherence to enhance the performance oF NV center in QiP.