This thesis presents work on the development of an atomic clock using bosonic potassium (39K and 87Rb) in order to study the role of inter-atom interactions on an atomic time standard. The project designed and constructed an RF circuit and RF antenna to manipulate the internal hyper fine states of the ultra-cold atoms. We developed an optical trap to trap these atoms in a vacuum cell, and performed several tests to check their behavior and measure their temperature. We performed experiments to observe Rabi flopping between the hyper ne states of the atoms. The eventual goal of this project is to create an operational atomic clock and observe the effects of inter-atom interactions.
This thesis presents work on the development of an atomic clock using bosonic potassium (39K and 87Rb) in order to study the role of inter-atom interactions on an atomic time standard. The project designed and constructed an RF circuit and RF antenna to manipulate the internal hyper fine states of the ultra-cold atoms. We developed an optical trap to trap these atoms in a vacuum cell, and performed several tests to check their behavior and measure their temperature. We performed experiments to observe Rabi flopping between the hyper ne states of the atoms. The eventual goal of this project is to create an operational atomic clock and observe the effects of inter-atom interactions.
This thesis describes the design, construction, and testing of a radio frequency signal source for generating rapidly changing frequencies in a repeatable and phase continuous manner. The radio frequency (RF) signal is generated by a Direct Digital Synthesizer (DDS) which is controlled by a triggerable microprocessor unit which is itself remotely programmed through an Ethernet connection. Waveforms generated by the RF source can be used for direct RF evaporation or RF manipulation of magnetic trapping potentials for ultra-cold atoms on an atom chip. The ultimate objective of the project is to mix the RF signal with higher frequency carrier waves to generate microwaves for the manipulation of hyperfine states of ultra-cold atoms of potassium and rubidium.
This thesis presents the experimental scheme for a guided cold atom Sagnac interferometer. Although atom interferometers have become an established method for precision measurements, a feasible clock-scheme based on fully guided atoms has yet to be realised. Radio frequency potentials, generated by a chip, provide a means to create a compact, fully controllable guided atom interferometer. The experimental infrastructure for a rubidium cold atom system is built and characterised. A chip-based atomic clock scheme is presented, utilising state-dependent guiding around a ring shaped trap. The chip design to form the trap and operate the interferometer is presented, and a vacuum compatible PCB has been designed and commercially manufactured to provide atomic transport and compression towards an atom chip. This project is part of the larger MatterWave project. In collaboration with Birmingham and Crete, the Matterwave project aims to develop ultra-sensitive matter-wave interferometry for compact devices.
"The work presented in this thesis is concerned with the manipulation of laser- cooled rubidium atoms and the detection of small numbers of cold atoms using very sensitive light detectors. Laser-cooled atoms are atoms that have been slowed to very low velocities, corresponding to temperatures of the order of 100 //K, and they can be trapped in magnetic and/or optical traps. The advantage of using cold atoms for experiments in atomic and quantum physics stems from the fact that these atoms are effectively confined within a region of space and this provides longer interaction and observation times compared to atoms at room temperature. Hence, it is possible to explore and observe a number of effects that would otherwise be extremely challenging. The achievement of laser cooling and trapping of neutral atoms was a major breakthrough in the mid 80’s and has resulted in significant advances being made in modern spectroscopy, the realisation of Bose-Einstein condensation, atomic clocks, and quantum information technologies amongst others. In particular, the work focuses on two theoretical proposals for developing microtraps for cold rubidium atoms involving (i) ultrathin optical fibres and (ii) wavelength sized apertures in thin films. In addition, a number of experimental techniques are explored with emphasis on the detection of small numbers of atoms near ultrathin optical fibres using both avalanche photodiodes and single photon detectors. A study on the interactions between atoms and photons is crucial for a full understanding of quantum mechanical processes at the few atom scale and detection schemes sensitive to very low levels of fluorescence from the laser-cooled atoms are vital for attaining this goal. Finally, an experimental study on the design and fabrication of arrays of silica microdisks, that could be used for facilitating interactions between cold atoms and photons, is presented."
Field-grade atomic clocks capable of primary standard performance in compact physics packages would be of significant value in a variety of applications ranging from network synchronization and secure communications to GPS hold-over and inertial navigation. A cold-atom coherent population trapping (CACPT) clock featuring laser-cooled 87RB atoms and pulsed Ramsey interrogation is a strong candidate for this technology if the principal frequency shifts can be controlled and the performance degradation associated with miniaturization can be overcome. In this thesis, research focused on the development of this type of compact atomic clock is presented. To address the low atom numbers obtained in small cold-atom sources, experiments were performed in which an atomic beam was decelerated with bichromatic stimulated laser forces and loaded into a mm-scale magneto-optical trap, increasing the atom number by a factor of 12.5x. A CACPT clock using the high-contrast lin||lin optical interrogation technique was developed and achieved a stability of 7 × 10-13 after one hour of integration. Doppler shifts in the clock are explained using a simple kinematic model and canceled by interrogating the atoms with a counter-propagating CPT configuration. Finally, a thorough characterization of the AC-stark effect in lin||lin CPT was performed. Observed shifts are explained in terms of contributions from coherent CPT-generating couplings and population transfer effects caused by optical pumping from incoherent light. Measurements are compared with existing and new theoretical treatments, and a laser configuration is identified that reduces clock drift from light shifts to less than 10-14 for the current system.
The advances in laser cooling and trapping techniques allow samples of ultra-cold atoms to be created and controlled for the study of quantum physics. In this thesis, we focus on using ensembles of cold atoms to investigate novel quantum effects and their applications in quantum optics. Realization of a scalable intercontinental quantum system, e.g. a global quantum internet, relies on quantum memories with long lifetimes on the order of seconds. We have reduced the differential light shifts of the atomic ground states to a sub-Hz level and achieved a lifetime of 16 seconds. Achieving fast and efficient quantum operations, on the other hand, requires strongly-interacting systems. We explore highly excited Rydberg atoms towards this goal and demonstrate Rydberg excitation blockade, many-body Rabi oscillations, trapping of Rydberg atoms, deterministic single photon source, and atom-photon entanglement. Finally, we integrate the two essential capabilities for quantum information processing, fast quantum state generation and long-term storage, by simultaneously exploiting Rydberg levels for interactions and ground atomic levels for the storage of quantum state. Our work advances the control of coherence properties and interactions in cold atomic ensembles to a new level and opens new opportunities for studies of complex quantum systems.
This thesis describes the construction of a dual species setup using fermionic 40K and bosonic 87Rb with the goal of cooling to ultracold temperatures and quantum degeneracy, and also perfoming precision collision experiments using a novel optical collider. The setup is composed of a dual species magneto-optical trap, with transfer to an ultrahigh vacuum science cell achieved using a mechanical transport scheme. Atoms are cooled to ultracold temperatures using forced radio frequency evaporation in a Ioffe-Pritchard style magnetic trap. The optical collider utilises the optical dipole force to trap a sample of ultracold atoms and accelerate them towards a target sample using an acousto-optic modulator. The process of cooling 87Rb atoms in the |F = 2, mF = 2> hyperfine state to Bose-Einstein condensation is described, as well as progress towards production of ultracold 40K. Design, implementation, and characterisation of the optical collider is provided, showing that it is a precision metrology device.