We developed a dual molasses technique which enabled us to perform high-sensitivity in situ fluorescence imaging of ytterbium (Yb) atoms in a two-dimensional optical lattice prepared in a thin glass cell. This technique successfully combines two different kinds of optical molasses for Yb atoms, that is, the one using the 1S0–1P1 transition which provides high-resolution in the in situ fluorescence imaging and the other using the 1S0–3P1 transition for cooling the atoms in the optical lattice. We performed in situ imaging of 174Yb atoms and could observe a Moiré pattern with a period of about 6 µm produced by the molasses beam with 556 nm and the optical lattice with 532 nm, which implies that the temperature was kept below the lattice depth during the fluorescence imaging. The number of photons per atom is estimated to be enough for single atom detection with our imaging system. This result is quite promising for the realization of an Yb quantum gas microscope.
We developed a dual molasses technique which enabled us to perform high-sensitivity in situ fluorescence imaging of ytterbium (Yb) atoms in a two-dimensional optical lattice prepared in a thin glass cell. This technique successfully combines two different kinds of optical molasses for Yb atoms, that is, the one using the 1S0–1P1 transition which provides high-resolution in the in situ fluorescence imaging and the other using the 1S0–3P1 transition for cooling the atoms in the optical lattice. We performed in situ imaging of 174Yb atoms and could observe a Moiré pattern with a period of about 6 µm produced by the molasses beam with 556 nm and the optical lattice with 532 nm, which implies that the temperature was kept below the lattice depth during the fluorescence imaging. The number of photons per atom is estimated to be enough for single atom detection with our imaging system. This result is quite promising for the realization of an Yb quantum gas microscope.
We demonstrate site-resolved imaging of individual bosonic 174Yb atoms in aHubbard-regime twodimensional optical lattice with a short lattice constant of 266 nm. To suppress the heating by probe light with the 1S0- 1P1 transition of the wavelength λ = 399 nmfor high-resolution imaging and preserve atoms at the same lattice sites during the fluorescence imaging, we simultaneously cool atoms by additionally applying narrow-line optical molasses with the 1S0 3P1 transition of the wavelength λ = 556 nm.We achieve a lowtemperature of T = 7.4(13) μK, corresponding to amean oscillationquantum number along the horizontal axes of 0.22(4) during the imaging process.Wedetect, on average, 200 fluorescence photons from a single atom within a 400 ms exposure time, and estimate a detection fidelity of 87(2)%. The realization of a quantum gas microscope with enough fidelity for Yb atoms in a Hubbard-regime optical lattice opens up the possibilities for studying various kinds of quantum many-body systems such as Bose and Fermi gases, and their mixtures, and also long-rangeinteracting systems such as Rydberg states.
続紙 １ ) 京都大学 博 士(理 学) 氏名 柴田 康介 論文題目 High-sensitivity in situ imaging of atoms in an optical lattice with narrow optical transitions (狭線幅光学遷移を用いた光格子中の原子の高感度その場イメージング) (論文内容の要旨)Development of laser cooling techniques in recent decades has enabled us to study neutral atoms in a quite controlled way.Cold neutral atoms have been used as a platform to study intriguing quantum many-body phenomena such as Bose-Einstein condensation and Bardeen-Cooper-Schriefer-Bose-Einstein condensation crossover.The excellent controllability of a cold atom system allows us precise measurements with unprecedented accuracy, which provides wide applications, such as an atomic clock.Another important application of cold atoms is quantum information processing.Internal degrees of freedom of a trapped cold atom can be regarded as a well-defined quantum bit (qubit) and quantum gate operations are realized by moderate internal or external interaction.In such cold atom research, a probing method plays an important role.In fact, one of the advantages of cold atom research is the ability to "see" atoms directly by taking images of the atoms via resonant or near-resonant light to the atoms.Among various developments in probing techniques, high-sensitivity detection is of particular importance, especially in the study of a simple system of a few atoms.While high-sensitivity detection and imaging were demonstrated with alkaline metals, there has been increasing interest on a different kind of atomic species.One attractive atomic species is ytterbium.Ytterbium is an alkaline-earth-like-metal atom and has several unique features, such as the rich variety of isotopes of two fermions and five bosons, and the existence of long-lived metastable electronic states.These features offer various possibilities in quantum many-body physics research and are also advantageous to quantum information processing as well as precision measurement.Therefore, a high-sensitivity imaging of ytterbium atoms will bring about a significant development in cold atom research.Under these backgrounds, this thesis reports on the successful demonstration of highsensitivity in situ imaging of ytterbium atoms in a two-dimensional optical lattice.The applicant demonstrated fluorescence imaging of ytterbium atoms in an optical lattice using optical molasses with a narrow optical transition of the wavelength 556 nm ("green molasses"), providing the Doppler cooling limit temperature low enough compared to the typical optical lattice depths.The applicant successfully observed a spatial modulation of fluorescence intensity with a period of approximately 6 μm as a result of the interference between the lattice period of 266 nm and the period of the standing-wave optical molasses of 278 nm.This pattern indicates that the temperature was sufficiently lower than the lattice potential so that the atoms emitted fluorescent photons around the bottom of the lattice sites
We demonstrate site-resolved imaging of individual bosonic atoms in a Hubbard-regime two-dimensional optical lattice with a short lattice constant of 266 nm. To suppress the heating by probe light with the 1 S 0 – 1 P 1 transition of the wavelength λ = 399 nm for high-resolution imaging and preserve atoms at the same lattice sites during the fluorescence imaging, we simultaneously cool atoms by additionally applying narrow-line optical molasses with the 1 S 0 – 3 P 1 transition of the wavelength λ = 556 nm. We achieve a low temperature of , corresponding to a mean oscillation quantum number along the horizontal axes of 0.22(4) during the imaging process. We detect, on average, 200 fluorescence photons from a single atom within a 400 ms exposure time, and estimate a detection fidelity of 87(2)%. The realization of a quantum gas microscope with enough fidelity for Yb atoms in a Hubbard-regime optical lattice opens up the possibilities for studying various kinds of quantum many-body systems such as Bose and Fermi gases, and their mixtures, and also long-range-interacting systems such as Rydberg states.
In this thesis I report a microscope system for fluorescence imaging of ultra-cold ytterbium atoms trapped in a two-dimensional optical lattice with single-site resolution.Having a rich variety of isotopes, ytterbium atoms trapped in two-dimensional optical lattices are a promising tool to study many-body quantum phenomena resulting from strongly interacting systems.In particular, quantum simulators using fermionic atoms are useful for studying the Fermi-Hubbard model, which is expected to be the key to elucidate the mechanism of high temperature superconductors.In order to observe atoms trapped in an optical lattice, a large number of photons is required to obtain a well resolved image.In contrast with to the conventional method of lasercooling the atoms while observing their fluorescence, in this experiment a deep potential was created using a combination of a shallow ground-state and a deep excited-state potentials, which confines the heated atoms during the imaging process.The resulting quantum gas microscope was able to resolve individual lattice sites in an optical lattice with a 544 nm spacing.And I'm not happy with all the analyses that go with just the classical theory, because nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical, and by golly it's a wonderful problem, because it doesn't look so easy.
Our knowledge on ultracold quantum gases is strongly influenced by our ability to probe these objects. In situ imaging combined with single atom sensitivity is an especially appealing scenario as it can provide direct information on the structure and the correlations of such systems. For a precise characterization a high spatial resolution is mandatory. In particular, the perspective to study quantum gases in optical lattices makes a resolution well below one micrometer highly desirable. Here, we report on a novel microscopy technique which is based on scanning electron microscopy and allows for the detection of single atoms inside a quantum gas with a spatial resolution of better than 150 nm. Imaging a Bose-Einstein condensate in a one-dimensional optical lattice with 600 nm period we demonstrate single site addressability in a sub-um optical lattice. The technique offers exciting possibilities for the preparation, manipulation and analysis of quantum gases.
We report a high-resolution microscope system for imaging ultracold ytterbium atoms trapped in a two-dimensional optical lattice. By using the ultraviolet strong transition combined with a solid immersion lens and high-resolution optics, our system resolved individual sites in an optical lattice with a 544-nm spacing. Without any cooling mechanism during the imaging process, the deep potential required to contain the atoms was realized using a combination of a shallow ground-state and a deep excited-state potentials. The lifetime and limitations of this setup were studied in detail.