【作者】 王娟；

【导师】 武海斌；

【作者基本信息】 华东师范大学 ， 光学， 2020， 硕士

【摘要】 量子系统中的噪声对揭示其根本的内在物理机制具有重要的作用,通常由其组成系统的基本粒子的统计和多体相互作用所决定。对于玻色子粒子,比如光子和中性玻色原子,所观测到的相关噪声特性可以找到经典的对应物,可用具有波动相位的经典场描述来解释;然而在费米子粒子组成的系统中观察到的反聚束只能用量子特性来描述。超冷中性费米气体由于其参数可精确调控为研究相关噪声特性提供了一个很好的平台。在高温的情况下,原子气体服从经典的玻尔兹曼分布,气体的密度涨落为泊松分布,反映了体系的无(弱)关联性质。在低温的情况下,特别是当原子温度降低进入量子简并区域时,量子统计逐步占据主导作用。在超冷量子体系中由于原子种类的不同将遵循不同的量子统计规律,在s波散射主导时,对于理想的玻色气体,其原子密度的量子涨落会被加强,而对于理想的费米气体,由于泡利排斥效应的影响,原子间密度涨落则会得到有效的抑制。本论文在实验上制备了超冷相互作用可调控的~6Li费米原子气体,研究了理想的费米气体的密度分布噪声关联特性。通过精确测量从光学势阱中直接展开的费米原子标准吸收图像中的原子散粒噪声,实验上实现了约20万个费米原子的亚泊松分布,揭示了原子统计在量子密度噪声中的重要关联特性。在量子简并条件下,研究了理想的费米气体的空间原子噪声涨落和量子简并度之间的关系。当费米气体温度较高时,原子密度涨落服从泊松分布;而当费米气体的温度趋近于绝对零度时,由于泡利排斥作用,原子数涨落被极大的抑制,表现为亚泊松涨落分布,并且这种抑制效应会随着温度的降低而更加明显。我们将进一步利用当前发展的精确测量技术去研究强相互作用或光学晶格中的超冷费米气体的密度涨落,其量子统计关联和噪声抑制可以表征费米气体在晶格中的有序性和温度以及在光晶格Mott绝缘相变和反铁磁相变等研究有着重要的应用价值。更多还原

【Abstract】 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.更多还原