Quantum Sensing Based On Fiber-coupled Diamond Sensor

Precision measurement at the microscopic scale has attracted much attention in recent years,which leads to a rapid development of quantum sensing technology based on the basic principles of quantum mechanics.The accuracy of classic measurement technology is often limited by factors such as diffraction limit and shot noise,and it is difficult to further improve the measurement accuracy.Quantum sensing is an important direction of quantum technology.It aims to use the entanglement,compression,and high-order correlation properties of quantum systems to achieve high-precision measurement of various physical quantities.So far,the systems of quantum sensing include neutral atoms,super-conducting circuits,and solid-state spins,and all of these have gradually moved from prototypes to industrialization.The nitrogen-vacancy(NV)center is a one of defect in diamond,which has a stable energy lever system and fluorescence emitting,long coherence time at room-temperature,as well as optical initialization and readout of spin state.Thus NV centers have been used for quantum computing,quantum communication and quantum sensing for a long time.Compared with other quantum system,nitrogen-vacancy centers benefit for sensing duo to their small size,stability,room-temperature performance and theoretically high sensitivity.Although the sensitivity has been continuously improved recently,most of systems become much more complex.Additionally,accompanied by stability issues,these systems are difficult to be practical.studies the method of coupling diamond containing high-concentration color centers to optical fibers,which realizes the high-sensitivity detection of physical quantities of magnetic field and temperature by the detector.It also provides a practical solution for the practical application of nitrogen-vacancy color center sensing.The following are the main tasks completed in this paper:This thesis mainly studies the applications of NV centers in the field of quantum sensing.According to the quantity of quantum sensors,they are mainly divided into the research of single NV center and ensemble NV centers.The former is mainly carried out under the confocal light path.And the latter couples a small piece of diamond sample with an optical fiber.In this case,the laser excitation and collection are realized by the same optical fiber.This system has the following advantages:stable system,high sensitivity,portability,extensibility and integration.The NV center in diamond can interact with magnetic field,temperature,electric field,pressure as well as the stress in the environment,and finally leads to the ground energy level splitting or drift.With the employment of fiber-based diamond sensor,this paper has performed magnetic field and temperature measurement:1.The construction of the diamond optical fiber sensing system.By coupling a small piece of diamond sample with an optical fiber,the laser excitation and fluorescence collection are simplified.This system has the following advantages:stable,high sensitivity,portability,extensibility and integration.Importantly,such system can be functioned as a sensor.2.Magnetic field detection?The pulse sequence control method was used to sensing the magnetic field from DC to MHz,where the DC magnetic field sensitivity of 72pT/(?)was realized.Finally,the continuous ODMR method was applied to microwave field sensing,which makes the detection of the magnetic field across a range from DC to GHz.In addition,the optical fiber sensor successfully realized the surface magnetic field mapping of the sample,indicating the practicability of the sensor in magnetic field detection.3.Temperature detection.Such optical fiber sensor can also realize temperature measurement.Frequency modulation ODMR detection can eliminate the influence of external magnetic field and microwave power drift on temperature detection,and finally realized a temperature sensitivity of 1mK/(?).The sensor was finally used as a probe to scan the temperature distribution on the surface of the working chip,which indicated the practicality of the sensor in temperature detection.In short,we have coupled the diamond with ensemble NV color centers with the optical fiber,and successfully achieved high-precision detection of magnetic field and temperature signals,which is of great significance for the application of quantum precision measurement.