Coherent Control And Application Of Spin Defects In Silicon Carbide

Silicon carbide(SiC)is a promising semiconductor material.It is a wide-gap mate-rial with excellent thermal conductivity,high transparency,radiation resistance,mature large-scale growth,and processing technology.It has been widely used in various fields such as automobiles,aerospace,microelectronics,etc.With the rapid development of quantum technology,some spin qubits in SiC have been discovered,which can be co-herently manipulated even at room temperature.These spin qubits can form multi-bit systems by coupling with the surrounding nuclear spins.And the qubits also can be cou-pled with another farther electron spin system through the spin-optical interface.The solid-state quantum system can be used for quantum registration,cluster state computa-tion,and distributed quantum computing,becoming an indispensable part of the future of hybrid quantum computing.Besides,the solid-state spin system also can be used for quantum sensing.Such as nitrogen-vacancy(NV-)color center in diamond,after decades of development,has been widely used in biological cells,atomic and molecular detection,electric field and magnetic field detection,extreme pressure detection,and other aspects.And there are some very excellent experimental results.However,the NV-center has its limitations,such as the difficulty of large-scale growth and process-ing of materials,the fluorescence wavelength band in the visible band,and the excessive transmission loss in fiber.However,for vacancies in SiC,the fluorescence wavelength from silicon-vacancy and divacancy is in the infrared band,with low transmission loss in fiber.Moreover,the SiC has mature large-scale growth and processing technology.In the future,it has excellent advantages in fiber communication and large-scale quan-tum devices application.My research is based on the color center in SiC.Next,I will introduce my work during my Ph.D.from four aspects.1.Preparation and characterization of a novel spin-defect center(PL8)in silicon carbide.First of all,I introduce the preparation of spin defects in SiC in this chapter.Since SiC has a diatomic structure,it has rich spin color center kinds.For 4H-SiC,there are silicon-vacancies(Siv-)for single defect vacancies and divacancy(VcVsi)for PL1 to PL7 named by the fluorescence wavelength and other transition metal defects,and so on.We introduced a new type of spin defect in this experiment,named PL8,based on its fluorescence wavelength.Generally,the different defects have their correspond-ing annealing temperature,like annealed at 950? for divacancy generated.But the PL8 center requires annealing at a temperature up to 1300 K,which is higher than the divacancy required.The zero-phonon line(ZPL)and the zero-field splitting(ZFL)pa-rameter are not matched any color center vacancies previously reported.Therefore,we determine that the PL8 color center is a new type of spin defect.In the experiment,we characterized its optical properties and spin properties and achieved coherent manipu-lation at room temperature and low temperature.The PL8 center is expected to be used in high-temperature quantum sensing and maser fields.2.Coherent manipulation of defect spins in SiC at high temperatures(550 K).Based on the spin defects preparation in the previous chapter,we explored the coherent properties of the divacancy spin defect(PL5)in 4H silicon carbide at high temperatures in this chapter.And according to the characteristics of its spin resonance frequency varying with temperature,we designed a temperature sensor that relies on Ramsey oscillation.General spin quantum systems have stringent temperature require-ments.For example,silicon-based superconductors qubits and doped qubits require ex-tremely low-temperature environments(?mK).Our experiments have proved that the divacancy centers(PL5)in SiC can be coherently manipulated at an ambient tempera-ture up to 550 K.The work lays the foundation for us to establish an anti-interference quantum system in the future.And based on the polynomial relationship of the reso-nance frequency with temperature,we experimentally realized temperature sensing of about 440 K.3.The magnetic-field-dependent spin property of spin defect in SiC at room temperature.For the spin defects,the external temperature and magnetic-field environment would affect its spin properties.In this chapter,I explore the relationship between the coherent properties of the spin ensemble and the external magnetic field environment.Analyz-ing the relationship between spin properties and the magnetic field is very important for realizing all-optical magnetic field detection and extending the coherence time.In this experiment,we systematically studied the relationship between the spin property of PL6 and the magnetic field by precisely adjusting the permanent magnet position.We compared two samples with different spin noise baths.Sample A generates the spin va-cancies from inherently produces during the growth process.Its coherent time is longer,and the surrounding noise bath of the defect spin is relatively weak.Sample B generates the spin vacancies by N ion(N2+)injection,and its coherent time is somewhat shorter,and the surrounding noise bath is relatively severe.We compared the coherence time changes of defect spin with the magnetic field under the two different surrounding spin noise baths.And we found that the coherent spin properties change more severely with the magnetic field angle for the samples with severe spin noise.4.Implemented the Online algorithm at room temperature using spin qubits in SiC.The demand for exponentially increasing data processing in real life has made the Online algorithm more and more popular.In this chapter,we use a single qubit implementing the Online algorithm for the first time.We studied the(n,p,k,r,w)-PNH problem,which can also be called the hat number parity problem.Compared with the classic bit,qubits will have a higher success rate in algorithm implementation for the same number of bits.In addition,we also increase the success rate by introducing Advice.In the case of providing Advice,the performance of quantum is also more excellent.