This thesis describes the experimental realisation of state-dependent traps employing RF-dressed adiabatic potentials. Rb-87 atoms have been successfully confined to chip-based atom traps that can independently address atomic ground states defined by the total angular momentum, F. The ring-shaped trap can be used as a Sagnac interferometer to measure rotation with respect to the inertial frame of reference. The results of spatially dependent radio frequency field polarisation control in this trap resulted in counterpropagating motion of the atoms in the F = 1 and F = 2 states.
This thesis describes the experimental realisation of state-dependent traps employing RF-dressed adiabatic potentials. Rb-87 atoms have been successfully confined to chip-based atom traps that can independently address atomic ground states defined by the total angular momentum, F. The ring-shaped trap can be used as a Sagnac interferometer to measure rotation with respect to the inertial frame of reference. The results of spatially dependent radio frequency field polarisation control in this trap resulted in counterpropagating motion of the atoms in the F = 1 and F = 2 states.
The manipulation of ultracold atoms in radio-frequency (RF)-dressed potentials offers unique advantages over static magnetic traps, such as the ability to create more complex potential landscapes, better control of atomic states, and increased robustness to environmental noise. Among the accessible geometries, ring traps are particularly promising for atomic Sagnac interferometers, which can be used to measure rotational motion with high sensitivity. Here, the authors demonstrate the state-dependent transport of atoms in an RF-dressed ring trap on an atom chip. By exploiting the polarization-dependent coupling of RF fields to different atomic hyperfine states, the authors achieve controlled transport of atoms in opposite directions. This approach targets the development of compact, high-precision devices for applications in inertial navigation and rotation sensing.
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.
We describe our progress in the development of an atom based rotation sensor, which employs state-dependent trapping potentials to transport ultracold atoms along a closed path and perform Sagnac interferometry. Whilst guided atom interferometers are sought after to build miniaturized devices that overcome size restrictions from free-falling atoms, fully trapped interferometers also remove free-propagation along an atomic waveguide. This provides additional control of motion, e.g. removing wave-packet dispersion and enabling operation that remains independent of external acceleration. Our experimental scheme relies on radio-frequency and microwave-fields, which are partly generated via atom-chip technology, providing a step towards implementing a small, robust, and eventually portable atomic-gyroscope.
The process of atomic interferometry relies heavily on the underlying atomic manipulation methods that have been developed over the past few decades. The ability to manipulate the internal state dynamics of atoms, and precisely control their time-space co-ordinates both lend themselves to the improvement of the sensitivities of these devices, allowing for more precise measurements, and more in-depth exploration of the physical world. In this thesis the design of a state-dependent fully trapped interferometric transport is presented, wherein atoms are fully magnetically trapped for the entire duration of an interferometric sequence. Through use of Radio-Frequency dressed potentials, we are able to create a trapping system that is both robust, and able to create state-dependent trap that can be dynamically moved to create the mechanical basis for an interferometer. We also investigate the coherence time of a superposition of hyperfine states loaded into the interferometer, necessary for a Ramsey-Borde sequence, and find it is significantly lower than what would be required to perform interferometry. We then present how this lack in coherence time is due to a mismatch in trapping potentials that arises due to a slight discrepancy between gyromagnetic ratios in the two superpositional states. This mismatch broadens the transition linewidth, leading to a reduction in superposition coherence time. Finally, we lay out the theoretical groundwork, and experimental progress, in realising Microwave-Dressed potentials, which utilise the AC-Stark shift to adiabatically shift the trapping potentials of the atoms, reducing the mismatch and thus increasing the coherence time of the superposition.
Adiabatic dressed state potentials are created when magnetic substates of trapped atoms are coupled by a radio-frequency field. We discuss their theoretical foundations and point out fundamental advantages over potentials purely based on static fields. The enhanced flexibility enables one to implement numerous configurations, including double wells, Mach-Zehnder, and Sagnac interferometers which even allows for internal state-dependent atom manipulation. These can be realized using simple and highly integrated wire geometries on atom chips.
We present a method for the creation of closed-loop lattices for ultra-cold atoms using dressed potentials. We analytically describe the generation of trap lattices that are state-dependent with dynamically controlled lattice depths and positioning. In a design akin to a synchronous motor, the potentials arise from the combination of a static, ring-shaped quadrupole field and multipole radio-frequency fields. Our technique relies solely on static and radio-frequency (rf) magnetic fields, enabling the creation of robust atom traps with simple control via rf amplitudes and phases. Potential applications of our scheme span the range from quantum many-body simulations to guided Sagnac interferometers.