Precise Measurement Of Density Fluctuation In Ultracold ~6Li Fermi Gas

Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the particles.For bosonic particles,such as photons and bosonic neutral atoms,the observed correlated noise can be explained by the description of classical field with wave phase.However,the anti-bunching effect observed in the detection of fermionic particles can only be described by quantum properties.Due to great flexibility to control the external potential and interaction of atoms,the ultracold neutral Fermi gas provides a good plat-form for the study of the noise correlation in the many-body field.At high temperature,the atomic gas follows the classical Boltzmann distribution,and the density fluctuation of the gas is Poisson distribution,which reflects the non(weak)correlation property of the system.At low temperature,especially at the regime of deep quantum degeneracy,quantum statistics take effect and paly a very important role.In the ultracold quantum system,due to the different kinds of atoms,different quantum statistics show the distinct noise correlations.When the S-wave scattering is dominant,the quantum fluctuation of atomic density will be strengthened for the ideal Bose gas,while for the ideal Fermi gas,due to the Pauli exclusion effect,the inter-atomic density fluctuation will be effectively suppressed.In this thesis,we prepared ultracold~6Li Fermi gas by tuning the interaction by the so-called Feshbach resonance,and studied the density distribution of an ideal Fermi gas.By accurately measuring the atomic shot noise in the stan-dard absorption image of Fermi atom directly expanded from the harmonic trap potential,the sub Poisson distribution of about 200000 Fermi atoms is realized experimentally,and the important correlation characteristics of atomic statistic-s in the quantum density noise are revealed.Under the condition of quantum degeneracy,the relationship between the fluctuation of spatial atom noise and the quantum degeneracy of an ideal Fermi gas is studied.when the temperature of Fermi gas is high,the fluctuation of atomic density obeys the Poisson distri-bution;when the temperature of Fermi gas closes to absolute zero,because of the Pauli exclusion effect,the atomic number fluctuation is greatly suppressed,which is shown as the sub-Poisson fluctuation distribution,and the inhibition effect will be more obvious with the lower temperature.We will further study the density fluctuation of the ultracold Fermi gas in the strong interaction or optical lattice by using the currently developed precise mea-surement technology.Its quantum statistical correlation and noise suppression can characterize the order and temperature of Fermi gas in the lattice,and it has important application value in the research of Mott insulation phase transition and antiferromagnetic phase transition in the optical lattice.