Cold atoms laboratory in a hollow core fiber

Abstract

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 $^{85}\text{Rb}$ atoms of temperature $\sim$\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 $\sim$\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 $\sim$\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.