| Nuclear magnetic resonance(NMR)is one of the most important material explo-ration techniques in contemporary science.Since the first discovery of NMR in the 1940 s,The related science and technology have so far won five Nobel Prizes in the fields of biology,physics,chemistry and medicine.Its applications have also been ex?tensively applied to various fields of frontier science and social life,such as magnetic resonance imaging.However,how to obtain high sensitivity and high resolution mag-netic resonance spectroscopy has always been a challenging problem in the field of mag?netic resonance.The development of quantum technology has provided new methods for NMR investigation.In particular,high-sensitivity atomic magnetometers provide a revolutionary method of detection for NMR.In contrast to conventional high-field NM-R,ultralow-field NMR completely eliminates the dependence on expensive supercon-ducting magnets,and has the advantages of economy,portability,and extremely high magnetic field uniformity.This dissertation studies the topic of ultralow-field NMR and its applications.Based on a homebuilt ultralow-field NMR spectrometer with high sensitivity atomic magnetometers,systematic researches on quantum precision mea-surements,quantum control,high-resolution spectroscopy,etc.are carried out,and the following results are obtained:·An ultralow-field NMR spectrometer,which employs an atomic magnetometer as a means of detection,was built achieving a magnetic-field sensitivity of 10 fT/Hz1/2.To further overcome the common mode magnetic noise,an magnetic gradiometer was designed and implemented.In the gradiometer,one channel is used to detect NMR signals,the other channel is used to monitor noise,and finally the difference signal between the two channels provides common-mode noise cancellation.The realized magnetic gradiometer achieved a sensitivity of about 7 fT/Hz1/2,which represents the best level in the field of ultralow-field NMR and provides a promising technique for unshielded NMR in the future.·Ultralow-field NMR spectra of a lots of chemical samples were studied with the homebuilt ultralow-field NMR spectrometer.It is found that nuclear spin samples exhibit a completely different spectroscopy from their high-field NMR spectroscopy.The main features include direct observation of the zero-quantum coherence spectrum,the number of spectral lines for a sample depends on the direction of the magnetic field,and the asymmetric spectrum.The ultra-low field NMR spectroscopy we developed can be used to analyze the structure of matter,and to provide complementary information to high-field NMR.Based on the new ultralow-field NMR spectroscopy,a new kind of NMR magnetometer is realized.·Universal quantum control of nuclear spins at zero magnetic field is realized for the first time.Single-spin and two-spin operations are implemented with a composite pulse.At the same time,the method of evaluating the fidelity of quantum control is also developed.The quality of quantum control is evaluated,and the fidelity of single-spin and two-spin operations approaches 0.9960 and 0.9877,respectively.Ultralow-field NMR combined with high-fidelity quantum control technology is expected to facilitate important applications in fundamental physics,medicine and chemistry.·The experimental platform for hyperpolarizing Xeon gas is built.The Xeon gas is polarized by the collisions with optical-pumped rubidium atoms,and the polarization of Xeon gas reaches around 30%.Based on the homebuilt platform,a new Floquet-state maser is proposed and realized with a spectral line resolution of 0.3 mHz.It is further proposed to search for axions and axion-like particles beyond the standard model. |
PDF Full Text Request