We demonstrate a fiber-guided atom interferometer in a far-off-resonant trap (FORT) of 100 μK. The differential light shift (DLS) introduced by the FORT leads to the inhomogeneous dephasing of the tightly trapped atoms inside a hollow-core fiber. The DLS-induced dephasing is greatly suppressed in π/2-π-π/2 Doppler-insensitive interferometry. The spin coherence time is extended to 13.4 ms by optimizing the coupling of the trapping laser beam into a quasi-single-mode hollow-core anti-resonant fiber. The Doppler-sensitive interferometry shows a much shorter coherence time, indicating that the main limits to our fiber-guided atom interferometer are the wide axial velocity distribution and the irregular modes of the Raman laser beams inside the fiber. This work paves the way for portable and miniaturized quantum devices, which have advantages for inertial sensing at arbitrary orientations and in dynamic environments.
Coherent manipulation and interaction between atoms and light are the core ingredients in modern quantum science and technology. Various applications such as quantum computation, quantum memories and quantum sensors which are promising in future technologies, are currently under exploration. However, due to the diffraction nature of light, miniaturizing quantum systems involving atom-light interactions has been highly limited. To avoid diffraction, I load cold atoms into a hollow-core fiber (HCF) and demonstrate four major experiments inside the fiber: inertia-sensitive Mach-Zehnder atom interferometer, long-lived quantum spin coherence, light storage and creation of an array of Schr\"odinger cat states. In this thesis, I show the theoretical framework of each experiment and demonstrate experimentally a cold atoms quantum laboratory realized a HCF. Cold
85Rb atoms of temperature
∼\SI{6}{\micro\kelvin} are loaded into a Kagome type photonic crystal hollow-core fiber (HCF) through an optical trapping beam coupled into the HCF. I first demonstrate an inertia-sensitive Mach-Zehnder atom interferometer using two counter-propagating Raman beams. However, the short quantum spin coherence time of
∼\SI{100}{\micro\second} due to the differential AC stark shift from the trapping beam is a major obstacle to reaching high sensitivity of the optically trapped atom interferometer inside the HCF. By introducing a vector light shift from the dipole trap to cancel the differential scalar light shift, the quantum spin coherence time is increased to hundreds of milliseconds. The long quantum spin coherence time opens up possibilities for various quantum experiments in HCF. Here, I demonstrate light storage using atoms as the storage medium in the HCF. A maximum storage efficiency of \SI{3}{\percent} and storage time of over \SI{20}{\milli\second} is shown in this thesis. With the implementation of dynamical decoupling, the storage time is improved to
∼\SI{100}{\milli\second}. Moreover, I create a 1D array of Schr\"odinger cats states in facilitated by an optical lattice in the HCF and study its potential for applications in quantum sensing and quantum simulation in HCF. Both odd and even cat states are validated and their coherence properties are studied. This thesis realized the state-of-the-art quantum experiments that are miniaturized into a HCF. The results signify a promise in future quantum sciences and technologies with compact fiber-based devices.