UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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Item Degenerate mixtures of rubidium and ytterbium for engineering open quantum systems(2015) Vaidya, Varun Dilip; Porto, James V; Rolston, Steven L; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the last two decades, experimental progress in controlling cold atoms and ions now allows us to manipulate fragile quantum systems with an unprecedented degree of precision. This has been made possible by the ability to isolate small ensembles of atoms and ions from noisy environments, creating truly closed quantum systems which decouple from dissipative channels. However in recent years, several proposals have considered the possibility of harnessing dissipation in open systems, not only to cool degenerate gases to currently unattainable temperatures, but also to engineer a variety of interesting many-body states. This thesis will describe progress made towards building a degenerate gas apparatus that will soon be capable of realizing these proposals. An ultracold gas of ytterbium atoms, trapped by a species-selective lattice will be immersed into a Bose-Einstein condensate (BEC) of rubidium atoms which will act as a bath. Here we describe the challenges encountered in making a degenerate mixture of rubidium and ytterbium atoms and present two experiments performed on the path to creating a controllable open quantum system. The first experiment will describe the measurement of a tune-out wavelength where the light shift of $\Rb{87}$ vanishes. This wavelength was used to create a species-selective trap for ytterbium atoms. Furthermore, the measurement of this wavelength allowed us to extract the dipole matrix element of the $5s \rightarrow 6p$ transition in $\Rb{87}$ with an extraordinary degree of precision. Our method to extract matrix elements has found use in atomic clocks where precise knowledge of transition strengths is necessary to account for minute blackbody radiation shifts. The second experiment will present the first realization of a degenerate Bose-Fermi mixture of rubidium and ytterbium atoms. Using a three-color optical dipole trap (ODT), we were able to create a highly-tunable, species-selective potential for rubidium and ytterbium atoms which allowed us to use $\Rb{87}$ to sympathetically cool $\Yb{171}$ to degeneracy with minimal loss. This mixture is the first milestone creating the lattice-bath system and will soon be used to implement novel cooling schemes and explore the rich physics of dissipation.Item Ultracold Mixtures of Rubidium and Ytterbium for Open Quantum System Engineering(2014) Herold, Creston David; Porto, James V; Rolston, Steven L; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Exquisite experimental control of quantum systems has led to sharp growth of basic quantum research in recent years. Controlling dissipation has been crucial in producing ultracold, trapped atomic samples. Recent theoretical work has suggested dissipation can be a useful tool for quantum state preparation. Controlling not only how a system interacts with a reservoir, but the ability to engineer the reservoir itself would be a powerful platform for open quantum system research. Toward this end, we have constructed an apparatus to study ultracold mixtures of rubidium (Rb) and ytterbium (Yb). We have developed a Rb-blind optical lattice at 423.018(7) nm, which will enable us to immerse a lattice of Yb atoms (the system) into a Rb BEC (superfluid reservoir). We have produced Bose-Einstein condensates of 170-Yb and 174-Yb, two of the five bosonic isotopes of Yb, which also has two fermionic isotopes. Flexible optical trapping of Rb and Yb was achieved with a two-color dipole trap of 532 and 1064 nm, and we observed thermalization in ultracold mixtures of Rb and Yb. Using the Rb-blind optical lattice, we measured very small light shifts of 87-Rb BECs near the light shift zero-wavelengths adjacent the 6p electronic states, through a coherent series of lattice pulses. The positions of the zero-wavelengths are sensitive to the electric dipole matrix elements between the 5s and 6p states, and we made the first experimental measurement of their strength. By measuring a light shift, we were not sensitive to excited state branching ratios, and we achieved a precision better than 0.3%.Item Radiation reaction and self-force in curved spacetime in a field theory approach(2007-11-28) Galley, Chad; Hu, Bei-Lok; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation, in three parts, presents self-consistent descriptions for the motion of relativistic particles and compact objects in an arbitrary curved spacetime from a field theory approach and depicts the quantum and stochastic (part I), semiclassical (parts I and II), and completely classical regimes (part III). In the semiclassical limit of an open quantum system description, the particle acquires a stochastic component in its dynamics. The interrelated roles of noise, decoherence, fluctuations and dissipation are prominently manifested from a stochastic field theory viewpoint and highlighted with our derivations of Langevin equations for the particle in curved space, which are useful for studying influences imparted by a stochastic source. We also derive non-local and history-dependent equations for radiation reaction and self-force in a curved spacetime when the stochastic sources are negligible. When the scales of the mass and the field are very different, as for an astrophysical mass or compact object, the stochastic features of the system are strongly suppressed and the stochastic description yields a (semiclassical) effective field theory. The appropriate expansion parameter $\mu$ is the ratio formed by the size of the compact object and the background curvature scale. Within an effective field theory framework we derive the second order self-force and the leading order contributions to the equations of motion from spin-orbit and spin-spin interactions on a compact object. The finite size of the compact body affects its motion at $O(\mu^4)$ and the self-force at $O(\mu^5)$. These results are useful for constructing more accurate templates that the space-based interferometer LISA will need for parameter estimation. Within a purely classical setting we introduce a new framework that describes fully relativistic gravitating binary systems, possibly with comparable masses, and allows for the background geometry to dynamically respond with the motions and influences of the compact objects and gravitational waves. The approach self-consistently incorporates mutual action and backreaction on every component in the total system. We derive the equations of motion and identify the parameter regimes where this new approach is applicable with the aim of establishing a common framework applicable to the detection ranges of both LIGO and LISA interferometers.