The Development And Application Of The Pulsed Electron Paramagnetic Resonance Spectrometer

Quantum computation promises great advantages and prospects that theclassical computation cannot achieve. Solid state quantum computation basedon spins, one of the most important protocols of quantum computation, uses theelectron spin (nuclear spin) as the quantum bit (Qubit). The bene?ts of thishybrid qubit in the solid state system include the long coherent time, fast qubitmanipulation and single qubit measurement[1]. With the commercial pulsed elec-tron paramagnetic resonance (EPR) spectrometer, we have ?nished the followingwork:1. We have preserved electron spin coherence in solids by optimal dynamicaldecoupling[2]. We useγ-irradiated malonic acid single crystals as a test-bedto research the performance of the two types of dynamical decoupling pulses.The coherence time of the electron spins has been prolonged from 0.04μs to30μs. We also discussed the relevant decoherence mechanisms in this solidsystem.2. Dynamical decoupling technique has also been applied in the protection ofthe bipartite pseudoentanglement[3]. The lifetime of the pseudoentangledstates generated in the P:Si system has been extended from 0.4μs in theabsence of decoherence control to 30μs in the presence of a two-πdynamicaldecoupling sequence.However, the commercial spectrometer's ability of controlling the electronand nuclear spins is limited and cannot satisfy the requirement of the new scienti?cresearches. Thus we have designed and constructed homebuilt spectrometers andwe have ?nished the following works:1. We have built the X-band pulsed EPR spectrometer. The X-band spectrom-eter can provide 8 channel microwave pulses output with fast adjustable am-plitudes and phases which is not available for the commercial spectrometer.2. We have ?nished the construction of the S-band spectrometer which is Op-tical Detected Magnetic Resonance (ODMR) spectrometer and use it as aplatform for the research of the nitrogen-vacancy defect center (N-V cen-ter) in the diamond. We realize a room-temperature implementation of the Deutsch-Jozsa algorithm by encoding both a qubit and an auxiliary state inthe electron spin of a single N-V center[4].3. We experimentally investigate the performance of the quantum metrologywith dynamical decoupling technique. The application of the dynamical de-coupling pulses can improve the sensitivity of the phase estimation in thepresence of decoherence. The experiments are carried out on a single electronspin of a N-V center in the diamond which is designed as an interferometerfor sensing a small phase di?erence ?. By applying the dynamical decou-pling pulses which is to prolong the coherence time T2, we have successfullyobserved an enhancement of the performance of the quantum metrology.Compared with the multi-pass protocol with 1 pulse decoupling, the opti-mal value of ?? in decreased by a factor of～4. Overall, our multi-passprotocol under the protection of CPMG5 yields a precision enhancementfactor of～24 when compared with the result based on one single geometricpath.