論文 / 著書情報
Article / Book Information
題目(和文)

イッテルビウム量子気体顕微鏡

Title(English)

Quantum gas microscope for ytterbium atoms

著者(和文)

ﾐﾗﾝﾀﾞﾏﾙﾃｨﾝ

Author(English)

Martin Miranda

出典(和文)

学位:博士(理学),学位授与機関:東京工業大学,
報告番号:甲第10063号,授与年月日:2016年3月26日,
学位の種別:課程博士,
審査員:上妻 幹旺,金森 英人,古賀 昌久,西田 祐介,相川 清隆

Citation(English)

Degree:Doctor (Science),Conferring organization: Tokyo Institute of Technology,
Report number:甲第10063号,
Conferred date:2016/3/26,
Degree Type:Course doctor,
Examiner:,,,,

学位種別(和文)

博士論文

Category(English)

Doctoral Thesis

種別(和文)

論文要旨

Type(English)

Summary

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（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

専攻：
Department of

学生氏名：
Student’s Name

物性物理学

専攻

MIRANDA Martin Santiago

申請学位（専攻分野）： 博士
Academic Degree Requested

指導教員（主）：Academic Advisor(main)

指導教員（副）：Academic Advisor(sub)Doctor of（ 理学）上妻 幹旺 教授
田中 秀数 教授要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）This thesis is organized in seven chapters.
Chapter 1: Introduction – This chapter starts with an overview of the historical background of laser cooling and the Bose-Einstein condensate, followed by an explanation on the importance of quantum simulators for studying the physics of high temperature cuprate superconductors. A system of ultra-cold atoms trapped in periodical potentials created by light interference is a novel candidate for realizing quantum
simulation of the two-dimensional Fermi-Hubbard model (FHM). The FHM is believed to contain all the ingredients required to produce
d-wave superconductivity, which is the key for understanding the mechanism of the cuprate superconductors. The major obstacle to observe
the d-wave superconducting phase is to reduce the temperature of the atoms well below the Neel temperature (T/TF~0.01), which is muchsmaller than the best current attainable temperatures using ultra-cold atoms (T/TF~0.1). I continue the explanation with the introduction on
the concept of the “quantum gas microscope”, a high-resolution fluorescence imaging device capable of resolving individual atoms trappedin a two-dimensional optical lattice, which is useful for measuring and reducing the temperature of atoms. Finally, I mention the purpose ofthe thesis, which is to create a quantum gas microscope using ytterbium atoms for realizing the quantum simulation of the FHM.
Chapter 2: Ytterbium – This brief chapter mentions the properties of ytterbium atoms and the important energy levels used for theexperiment.
Chapter 3: Quantum gas microscope - In this chapter I explain the requirements to realize a quantum gas microscope, focusing on thefeasibility of applying different fluorescence imaging strategies to ytterbium atoms. Fluorescence techniques used on other quantum gas
microscopes (using Rb, Li and K) consists on cooling the atoms while observing the resultant fluorescence. The polarization gradientcooling, Raman cooling and electromagnetically induced transparency (EIT) cooling used in those experiments are not applicable to theytterbium species due to the absence of hyperfine splitting and the lack of Zeeman sublevels in the ground state. I continue the chapter
analyzing the possibility of applying Doppler cooling combined with magic-wavelength potentials as a fluorescence strategy. In addition, I
propose a new “deep potential” method, which consists in creating a very deep potential in the excited state and a shallow potential in theground one. The feasibility of the proposed method together with an analysis of the lifetime limitations are studied in detail with the help of
a semi-classical simulation. Finally, I introduce the concept of solid immersion lens (SIL), which is a semi-spherical lens useful for increasing the numerical aperture of the microscope system.
Chapter 4: Experiment: Transport of atoms to the SIL surface – To load ultra-cold ytterbium atoms into a two-dimensional opticallattice, the atoms are first required to be confined in a pancake-shaped region which is thinner than the depth of field of the objective lens.
This chapter focuses in the experimental method used to 1) create a cloud of ultra-cold ytterbium atoms using a Magneto-Optical trap, 2)transfer the cooled atoms to a distance of 20μm under the surface of the SIL using optical-tweezers, 3) create a Bose-Einstein condensateand 4) compress the condensate of atoms into a thin pancaked-shaped cloud. In order to create a condensate and compress it into a thin layer,
I realized a new technique for creating and manipulating an “optical accordion” under the surface of the SIL. The technique consists inreflecting an incident (accordion) beam into the flat surface of the lens which creates a standing wave with controllable periodicity. Detailsof this technique and analysis of the experimental results are fully covered in this chapter.
Chapter 5: Experiment: Fluorescence imaging - In this chapter, the experimental method to load the thin condensate of atoms under thesurface of the solid immersion lens into a two-dimensional optical lattice is first explained, followed by an analysis of the fluorescence
images that were obtained with the quantum gas microscope using the “deep potential” strategy proposed in chapter 3. The following
aspects of the microscope are covered: 1) resolution of the microscope, 2) algorithm used to reconstruct the original atomic distribution, 3)
lifetime analysis and 4) reconstruction fidelity.
Chapter 6: Extension to fermionic isotopes – Here, I explain the requirements to extend the quantum gas microscope of ytterbium atoms
to the 173Yb fermionic isotope. To determine whether the “deep potential” is possible in the presence of a hyperfine splitting interaction, thetotal Hamiltonian containing both the AC stark interaction and the hyperfine splitting interaction is numerically calculated. For high lightintensities, a breaking of the hyperfine splitting is observed as an analog to the Paschen-Back effect ocurring under high magnetic fields. In
consequence, I estimate that the current quantum gas experiment is applicable to the fermionic 173Yb fermionic isotope with only minorchanges.
Chapter 7: Conclusions – In the last chapter, after a brief summary of the experimental results, I compare the performance of the quantumgas microscope of ytterbium atoms presented on this work with different quantum gas microscope using other species, focusing on thecharacteristics of the “deep potential” method proposed here. I suggest some ideas to improve the performance of the microscope, as wellas mentioning the remaining tasks and future challenges.
備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of 2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800
Words (English).
注意：論文要旨は、東工大リサーチリポジトリ（T2R2）にてインターネット公表されますので、公表可能な範囲の内容で作成してください。
Attention: Thesis Summary will be published on Tokyo Tech Research Repository

Website (T2R2).