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1
Christensen, Caleb A. "Ultracold molecules from ultracold atoms : interactions in sodium and lithium gas." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68868.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 218-226).
The thesis presents results from experiments in which ultracold Sodium-6 and Lithium-23 atomic gases were studied near a Feshbach resonance at high magnetic fields. The enhanced interactions between atoms in the presence of a molecular state enhance collisions, leading to inelastic decay and loss, many-body dynamics, novel quantum phases, and molecule formation. Experimental data is presented alongside relevant theory and numerical models. Results are presented for both homonuclear Na 2 and Li 2 molecules, as well as heteronuclear NaLi resonances, although we were unable to isolate and measure NaLi molecules. Furthermore, experiments and theories related to strongly-correlated quantum phases such as Stoner model ferromagnetism, Bose mediated Fermi interactions, and Bose-Fermi mixtures are presented as applicable to Na and Li gases. Conclusions are presented regarding the feasibility of producing deeply bound, dipolar NaLi molecules, as well as future prospects for strongly interacting atomic gases of Na and Li.
by Caleb A. Christensen.
Ph.D.
2
Punk, Matthias. "Many-particle physics with ultracold gases." kostenfrei, 2010. https://mediatum2.ub.tum.de/node?id=956951.
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Savikko, M. (Mikko). "Efimov states in ultracold gases." Master's thesis, University of Oulu, 2014. http://urn.fi/URN:NBN:fi:oulu-201403111157.
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This work will introduce the Efimov effect and the resonant and scaling limits and derive the formula for the binding energies of the Efimov states. We use the hyperspherical coordinates for the stationary wave function of three particles and solve the low-energy Faddeev equation with the hyperspherical expansion and use the expansion for solving the channel eigenvalues. The channel eigenvalues are defined by a constant, which is the solution of the resulting transcendental equation. We also solve the scaling-violation parameter and finally compile all the results to derive the Efimov states. In the unitary limit we find infinitely many Efimov states, with an accumulation point at zero energy and an asymptotic discrete scaling symmetry with the discrete scaling factor of about 22.7.
In this work, we will also delve into effective field theories, which can be used to numerically analyze and solve Efimov states in different cases. We will first go through the two-body problem which is used as a simpler example on how to solve the three-body problem and to solve the two-body coupling constant, which will also appear in the three-body problem. By using the diatom field trick introduced by Bedaque, Hammer and van Kolck, we derive the Skorniakov-Ter-Martirosian equation for the three-body problem.
Finally this work will take a quick look at the first experimental evidences for Efimov states that were found since 2006. In the experiment, proper Efimov resonances in measurements of three-body recombination have been observed.
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Campbell, Daniel L. "Engineered potentials in ultracold Bose-Einstein condensates." Thesis, University of Maryland, College Park, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3725451.
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Bose-Einstein condensates (BECs) are a recent addition to the portfolio of quantum materials some of which have profound commercial and military applications e.g., superconductors, superfluids and light emitting diodes. BECs exist in the lowest motional modes of a trap and have the lowest temperatures achieved by mankind. With full control over the shape of the trap the experimentalist may explore an extremely diverse set of Hamiltonians which may be altered mid-experiment. These properties are particularly suited for realizing novel quantum systems.
This thesis explores interaction-driven domain formation and the subsequent domain coarsening for two immiscible BEC components. Because quantum coherences associated with interactions in BECs can be derived from low energy scattering theory we compare our experimental results to both a careful simulation (performed by Brandon Anderson) and an analytical prediction. This result very carefully explores the question of how a metastable system relaxes at the extreme limit of low temperature.
We also explore spin-orbit coupling (SOC) of a BEC which links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers that resonantly couple the ground electronic states of our BECs. SOC is used similarly in condensed matter systems to describe coupling between charge carrier spin and crystal momentum and is a necessary component of the quantum spin Hall effect and topological insulators.
SOC links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers and a subset of the ground electronic states of our BEC. The phases of an effective 2-spin component spin-orbit coupling (SOC) in a spin-1 BEC are described in Lin et al. (2011). We measure the phase transition between two phases of a spin-1 BEC with SOC which cannot be mimicked by a spin-1/2 system. The order parameter that describes transitions between these two phases is insensitive to magnetic field fluctuations.
I also describe a realistic implementation of Rashba SOC. This type of SOC is expected to exhibit novel many-body phases [Stanescu et al. 2008, Sedrakyan et al. 2012, Hu et al. 2011].
5
Wang, Tout Taotao. "Small Diatomic Alkali Molecules at Ultracold Temperatures." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226049.
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This thesis describes experimental work done with two of the smallest diatomic alkali molecules, 6Li2 and 23Na6Li, each formed out of its constituent atoms at ultracold temperatures. The 23Na6Li molecule was formed for the first time at ultracold temperatures, after previous attempts failed due to an incorrect assignment of Feshbach resonances in the 6Li+23Na system. The experiment represents successful molecule formation around the most difficult Feshbach resonance ever used, and opens up the possibility of transferring NaLi to its spin-triplet ground state, which has both magnetic and electric dipole moments and is expected to be long-lived. For 6Li2, the experimental efforts in this thesis have solved a long-standing puzzle of apparently long lifetimes of closed-channel fermion pairs around a narrow Feshbach resonance, finding that the lifetime is in fact short, as expected in the absence of Pauli suppression of collisions. Moreover, measurements of collisions of Li2 with free Li atoms demonstrates a striking first example of collisions involving molecules at ultracold temperatures described by physics beyond universal long-range van der Waals interactions.
6
Schneider, William. "Strong Correlations in Ultracold Fermi Gases." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316447449.
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Fancher, Charles. "Ac Zeeman Force with Ultracold Atoms." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499449866.
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Ultracold atom experiments use a gas of neutral atoms with temperatures less than 100 µK above absolute zero and offer unmatched experimental control of quantum states and coherence, which has allowed ultracold atom-based measurements to be some of the most precise to date. While ultracold atom experiments can control almost all atomic degrees of freedom, spin-dependent trapping and spatial manipulation has remained difficult if not inaccessible. We are developing a method of spin-dependent trapping and spatial manipulation for ultracold neutral atoms using the AC Zeeman force produced by a microwave magnetic near-field gradient generated by an atom chip. We measure the AC Zeeman force on ultracold rubidium atoms by observing its effect on the motion of atoms in free-fall and on those confined in a trap. We have studied the force as a function of microwave frequency detuning from a hyperfine transition at 6.8 GHz at several magnetic field strengths and have observed its characteristic bipolar and resonant features predicted by two-level dressed atom theory. We find that the force is several times the strength of gravity in our setup, and that it can be targeted to a specific hyperfine transition while leaving other hyperfine states and transitions relatively unaffected. We find that our measurements are reasonably consistent with parameter-free theoretical predictions.
8
Lee, Ye-Ryoung. "Ultracold Fermi gas with repulsive interactions." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79520.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 95-100).
This thesis presents results from experiments of ultracold atomic Fermi gases with repulsive interaction. Itinerant ferromagnetism was studied by simulating the Stoner model with a strongly interacting Fermi gas of ultracold atoms. We observed nonmonotonic behavior of lifetime, kinetic energy, and size for increasing repulsive interactions, which is in good agreement with a mean-field model for the ferromagnetic phase transition. However, later research showed the absence of enhanced spin fluctuation, which is definitive evidence against the ferromagnetic phase transition. Still, our work triggered a lot of research on repulsive interactions in ultracold Fermi gases. A quantitative approach is taken to study ultracold Fermi gases with repulsive interaction. This is done by careful measurements of density profiles in equilibrium. First, Pauli paramagnetism is observed in trapped atomic samples which have an inhomogeneous density due to the harmonic confinement potential. We experimentally measure the susceptibility of ideal Fermi gas. This research shows that ultracold atoms can serve as model systems to demonstrate well-known textbook physics in a more ideal way than other systems. Then, Fermi gases with repulsive interactions are characterized by measuring their compressibility as a function of interaction strength. The compressibility is obtained from in-trap density distributions monitored by phase contrast imaging. For interaction parameters kFa > 0.25 fast decay of the gas prevents the observation of equilibrium profiles. For smaller interaction parameters, the results are adequately described by first-order perturbation theory. A novel phase contrast imaging method compensates for dispersive distortions of the images.
by Ye-Ryoung Lee.
Ph.D.
9
Himsworth, Matthew. "Coherent manipulation of ultracold Rubidium." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72369/.
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The production of dense samples of atoms whose translational velocity can be parameterized by temperatures in the microkelvin range has revolutionized the fields of spectroscopy, metrology, quantum computing and sensitive tests of quantum mechanics. Such ultracold temperatures may be reached by Doppler cooling which uses a velocitysensitive scattering force. This technique relies upon atoms which have closed electronic transitions between two states so that the atoms may continuously absorb photon momenta and do not spontaneous decay into a dark state. Very few atoms fulfil this condition and attempts to cool molecules are inhibited by their extra degrees of freedom, via rotation and vibration, which add manifolds of extra states. This thesis describes the early experimental stages of investigation into coherent laseratom interactions which may be used as a general all-optical method to impart momentum to atoms and molecules and thus manipulate their velocity. The thesis covers the construction and operation of stable diode lasers, a magneto-optical trap to produce cold samples of the test species Rubidium and a high-power, phase and intensity, controllable laser to induce Raman transitions. Studies into the spectroscopy of Rubidium and the nature of coherent Raman interactions in multilevel atoms is also covered. Experimental results shows that coherent Raman transitions between the 5S1/2 ground states has been achieved in the form of sinc-squared lineshapes and Rabi-flopping.
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Nunnenkamp, Andreas. "Strong correlations in ultracold atomic gases." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:6e09e9d3-f5cd-4580-a667-6599203162e2.
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In this thesis we investigate strongly-correlated states of ultracold bosonic atoms in rotating ring lattices and arrays of double-well potentials. In the first part of the thesis, we study the tunneling dynamics of ultracold bosons in double-well potentials. In the non-interacting limit single-particle transitions dominate, while in the interaction-dominated regime correlated tunneling of all particles prevails. At intermediate times of the many-particle flopping process correlated states occur, but the timescales of these processes increase dramatically with the number of particles. Using an array of double-well potentials, a large number of such few-particle superposition states can be produced in parallel. In the second part of the thesis, we study the effects of rotation on ultracold bosons confined to one-dimensional ring lattices. We find that at commensurate filling there exists a critical rotation frequency, at which the ground state of the weakly-interacting gas is fragmented into a macroscopic superposition of different quasi-momentum states. We demonstrate that the generation of such superposition states using slightly non-uniform ring lattices has several practical advantages. Moreover, we show that different quasi-momentum states can be distinguished in time-of-flight absorption imaging and propose to probe correlations via the many-body oscillations induced by a sudden change in the rotation frequency. Finally, we compare these macroscopic superposition states to those occurring in superconducting quantum interference devices. In the third part of the thesis, we demonstrate the creation of entangled states with ultracold bosonic atoms by dynamical manipulation of the shape of the lattice potential. To this end, we consider an optical superlattice that allows both the splitting of each site into a double-well potential and the variation of the height of the potential barrier between the sites. We show how to use this array of double-well potentials to perform entangling operations between neighboring qubits encoded on the Zeeman levels of the atoms. As one possible application, we present a method of realizing a resource state for measurement-based quantum computation via Bell-pair measurements. In the final part of the thesis, we study ultracold bosons on a two-dimensional square lattice in the presence of an effective magnetic field and point out a couple of features this system has in common with ultracold bosons in one-dimensional rotating ring lattices.
11
Wu, Cheng-Hsun Ph D. Massachusetts Institute of Technology. "Strongly interacting quantum mixtures of ultracold atoms." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83817.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 198-202).
This thesis describes the construction of a new apparatus for ultracold quantum gases as well as the scientific results this machine has produced so far. This new apparatus is capable of simultaneously cooling and trapping lithium, sodium, and potassium. It therefore provides a platform to study a large variety of quantum mixtures. Three main experimental results are presented. Firstly, the direct cooling of "K to Bose-Einstein condensation is presented. Then the 41K atoms provide the coolant for 6Li and 40K, achieving a triply degenerate gas of 6Li -40K -41K. In particular, a broad interspecies Feshbach resonance between 40K -41K is observed, opening a new pathway to study a strongly interacting isotopic Bose-Fermi mixture of 40K -41K. Secondly, a new Bose-Fermi mixture of 23Na -40K is introduced. We show that 23Na is a very efficient coolant for 40K by sympathetically cooling 40K to quantum degeneracy with the help of a 23Na condensate. Moreover, over thirty interspecies Feshbach resonances are identified, paving the way to study strongly interacting Bose- Fermi problems, in particular the Bose polaron problem. Thirdly, we report on the first formation of ultracold fermionic Feshbach molecules of 23Na40K by radio-frequency association. The lifetime of the nearly degenerate molecular gas exceeds 100 ms in the vicinity of the Feshbach resonance. The NaK molecule features chemical stability in its ground state in contrast to the case of the KRb molecule. Therefore, our work opens up the prospect of creating chemically stable, fermionic ground state molecules of 23Na40K where strong, long-range dipolar interactions will set the dominant energy scale. Finally, the thesis concludes with an outlook on future topics in polaron physics and quantum dipolar gases, which can be studied using the new apparatus.
by Cheng-Hsun Wu.
Ph.D.
12
Vengalattore, Mukund T. 1977. "Atom-light interactions in ultracold anisotropic media." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34386.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (leaves 203-207).
A series of studies on atom-light interactions in ultracold anisotropic media were conducted. Methods to trap ultracold neutral atoms in novel traps with widely tunable trap frequencies and anisotropies were investigated. In comparison to conventional magnetic traps, it was found that magnetic traps generated by soft ferromagnets have various advantages such as a large dynamic range of trap confinement, an ability to create homogeneous reciprocal traps and an ability to shield ultracold atoms from deleterious surface induced effects which would otherwise lead to decoherence and loss. Such microfabricated ferromagnetic "atom chips" are promising systems for the integration of atom optic components such as high finesse cavities and single atom counters. This can, in the near future, lead to precise atom sensors for magnetometry and inertial sensing. the wide tunability of the trap parameters made such integrated atom traps and ideal system for studies of lower dimensional systems and mesoscopic physics in the ultracold regime. Ultracold anisotropic media were shown to possess many novel and attractive properties. Due to the suppression of radiation trapping in these systems, laser cooling was shown to be highly efficient leading to a dramatic increase in the phase space density of an optically cooled atomic ensemble. Subsequent confinement of the resulting ensemble in a magnetic trap and further increase of the phase space density by evaporative cooling should lead to large numbers of atoms in a Bose condensate. It is also an intriguing prospect to combine extreme trap anisotropy with sub-recoil cooling schemes to approach Bose condensation through all-optical cooling. Recoil induced resonances in these anisotropic media were shown to exhibit single pass optical amplifications on the order of 100, more than two orders of magnitude higher than observed previously. The strong dispersion associated with this resonance was used to create an ultracold optical fiber, thus overcoming the diffraction limit for atom-light interactions. With such radial confinement, strong dispersion was combined with arbitrarily large optical depths thereby rendering this system a unique medium for nonlinear optics in the single photon domain. This system was shown to exhibit pronounced nonlinear and collective effects due to the strong coupling between atoms and light.
by Mukund Vengalattore.
Ph.D.
13
Simpson, David Peter. "One dimensional transport of ultracold bosons." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5358/.
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This thesis concerns the transport of ultracold bosons in a one-dimensional geometry. I consider two three-dimensional reservoirs of Bose-Einstein condensed atoms that are connected via weak tunnel junctions to each end of a one-dimensional channel. The particle current along the channel is driven only by a constant phase difference between the two reservoirs. I theoretically investigate the bosonic flow and develop a non-perturbative mean field description, showing the existence of metastable solutions for all values of tunnelling. I show there are two separate branches of the mean field solution and the lowest energy solution necessarily jumps discontinuously between these branches. I then demonstrate that such a mean field solution is robust against fluctuations for values of the Luttinger parameter pertinent to bosonic atoms and that fluctuations do not connect different branches of the mean field solution. I provide a possible experimental realisation utilising the versatility of atom chips and describe how one can experimentally observe both the phase profile in the channel and the particle flow along the channel. Finally, I explore the non-equilibrium dynamics following a quench in the tunnelling energy and demonstrate that such a quench can lead to switching between different branches of the mean field solution.
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Denning, Adam W. "Early Dynamics of Ultracold Neutral Plasmas." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2481.pdf.
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Okan, Melih. "Controlling ultracold fermions under a quantum gas microscope." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115688.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-130).
This thesis presents the experimental work on building a quantum gas microscope, employing fermionic 40K atoms in an optical lattice, and precision control of the atoms under the microscope. This system works as a natural simulator of the 2D Hubbard model, which describes materials with strongly correlated electrons. After preparing ultracold 40K atoms in an optical lattice and performing Raman sideband cooling, single lattice site resolution was obtained. Metallic, Mott insulating, and band insulating states were observed in situ and local moment was directly accessed as a local observable with the site-resolved imaging. Performing spin-selective imaging also gave access to spin, and spatial correlations of charge and spin was measured with respect to doping. In this measurements, antiferromagnetic correlations were observed in the spin sector. In the charge sector, we observed an anti-bunching behavior at low fillings, as a result of the Pauli exclusion principle and repulsive interactions. We also observed that doublon-hole bunching resulting from the superexchange excitations dominates and causes the charges to bunch. In order to increase the simulation capabilities, we updated the microscope with arbitrary optical potential imprinting ability. Using a digital micromirror device (DMD), a 2D box potential was created with the sharpness of a few lattice sites. A homogenous 2D Hubbard system is created at half-filling in this box potential. Using a magnetic gradient, different spin states were separated within a Mott insulator, being an ideal starting point for performing spin transport measurements. The lowest energy s-wave Feshbach resonance between 19/2, -7/2) and 19/2, -5/2) states of 40K was characterized with an increased precision and established as an interaction varying knob of our quantum simulator. Interaction energy spectrum around this resonance was measured. Confinement induced molecules on the attractive side and deeply bound molecules on the repulsive side are observed in an optical lattice.
by Melih Okan.
Ph. D.
16
Zwierlein, Martin W. "High-temperature superfluidity in an ultracold Fermi gas." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39290.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2007.Includes bibliographical references (p. 258-280).
This thesis presents experiments in which a strongly interacting gas of fermions was brought into the superfluid regime. The strong interactions are induced by a Feshbach scattering resonance that allows to tune the interfermion scattering length via an external magnetic field. When a Fermi mixture was cooled on the molecular side of such a Feshbach resonance, Bose-Einstein condensation of up to 107 molecules was observed. Subsequently, the crossover region interpolating between such a Bose-Einstein condensate (BEC) of molecules and a Bardeen-Cooper-Schrieffer superfluid of long-range Cooper pairs was studied. Condensates of fermion pairs were detected in a regime where pairing is purely a many-body effect, the pairs being stabilized by the presence of the surrounding particles. Superfluidity and phase coherence in these systems was directly demonstrated throughout the crossover via the observation of long-lived, ordered vortex lattices in a rotating Fermi mixture. Finally, superfluidity in imbalanced Fermi mixtures was established, and its Clogston limit was observed for high imbalance. The gas was found to separate into a region of equal densities, surrounded by a shell at unequal densities.
by Martin W. Zwierlein.
Ph.D.
17
Schirotzek, Andre. "Radio-frequency spectroscopy of ultracold atomic Fermi gases." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/77482.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 143-154).
This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle interaction strength and the relative population of different Fermions allows to access very different physical regimes. Radio-frequency spectroscopy has been developed into an ideal tool to probe correlations between particles in these different phases. In particular, radio-frequency spectroscopy of highly population imbalanced atomic Fermi systems gives access to the impurity problem: A single Fermion, or Boson, immersed in a sea of Fermions constitutes a polaron, which can be described by Landau's Fermi liquid theory. A critical interaction strength can be identified separating the regime of a fermionic polaron and a bosonic polaron. Radio-frequency spectroscopy of the polarized superfluid phase allows an accurate measure of the superfluid gap [Delta] and allows to identify the importance of Hartree Mean-field energies. Furthermore, it is shown how these different physical regimes are connected.
by Andre Schirotzek.
Ph.D.
18
Hu, Jiazhong Ph D. Massachusetts Institute of Technology. "Light-induced many-body correlations in ultracold gases." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/115012.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-149).
In this thesis, we investigate several methods to generate and probe the quantum correlations in ultracold gases using light. A high-finesse optical cavity is used to enhance the atom-light interaction and we can produce a variety of entangled states which can overcome the standard quantum limit. The quantum correlations are generated by sending very weak light into the cavity which contains many neutral atoms. We control the properties of the incoming photon, such as the polarization and/or the frequency spectrum, to obtain the final atomic states as desired. The photon transmitted through the cavity interacts with the atomic ensemble and becomes entangled with the atomic state. The amount of entanglement strength is usually small but non-zero. Placing a detector after the cavity, the tiny amount of entanglement will be dramatically amplified once a photon is heralded in the detector. Using this method, we demonstrated the first observation of the negative Wigner function in the many-body system, and largely extended the record of the maximum number of atoms entangled. Other than engineering entangled many-body system, we have also worked on reaching the quantum degenerate regime for the atomic gas, in order to enhance quantum correlations in future experiments. Laser cooling all the way to Bose-Einstein condensation of an alkali atom is experimentally realized for the first time. We demonstrate a special technique suppressing the binary atomic loss at high atomic density. By transferring the atoms between two different optical traps, the atomic cloud is compressed and the density is increased. Combining these with the Raman sideband cooling method, we achieve the phase space density over 1, and observe the bimodal velocity distribution characteristic of a Bose-Einstein condensate.
by Jiazhong Hu.
Ph. D.
19
Smith, Dane Hudson. "Resonant Floquet scattering of ultracold atoms." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1478192866433031.
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Pattie, Robert. "Precision Tests of the Standard Model with Ultracold Neutrons." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/5593.
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Simonet, Juliette. "Optical traps for Ultracold Metastable Helium atoms." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00651592.
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Les thématiques abordées dans ce mémoire illustrent deux spécificités des gaz ultrafroids d'Hélium métastable : la possibilité de comparer les résultats expérimentaux à des évaluations théoriques précises (niveaux d'énergie, potentiels d'interaction) et une méthode de détection originale fournie par les ionisations Penning. Nous présentons la construction et la caractérisation d'un nouveau piège magnétique offrant un large accès optique et permettant ainsi de combiner la production d'un condensat de Bose-Einstein et son chargement in situ dans un réseau optique 3D. Les fondements théoriques des expériences prévues dans ces potentiels optiques sont ensuite détaillés. Dans un piège dipolaire croisé, l'influence du champ magnétique, devenu un paramètre libre, sur les taux de collisions Penning peut être mesurée et comparée à une nouvelle évaluation théorique. Concernant l'Hélium dans des réseaux optiques, deux sujets sont développés : l'effet du confinement sur les collisions inélastiques Penning (réseau 1D), ainsi que la modélisation des pertes Penning dans un modèle de Bose-Hubbard dissipatif (réseau 3D). Enfin, nous présentons la première mesure directe de la transition dipolaire magnétique 23S1 vers 23P2, liant les familles singulet et triplet de l'Helium 4. Cette expérience de spectroscopie, réalisée en collaboration avec le groupe de W. Vassen (LaserLab - Amsterdam), allie le domaine des atomes froids aux techniques des peignes de fréquences, afin d'obtenir une précision de 5 kHz.
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Gildemeister, Marcus. "Trapping ultracold atoms in time-averaged adiabatic potentials." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:0572480a-9114-426e-b853-b6be30c7594e.
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This thesis describes the trapping and manipulation of ultracold atoms in time-averaged adiabatic potentials (TAAP). The time-averaged adiabatic potential, proposed in [Phys. Rev. Lett. 99, 083001 (2007)], uses resonant radio frequency (rf) radiation to couple the different magnetic substates of a hyperfine level manifold. The resultant dressed states are time-averaged and produce smooth and versatile trapping geometries. More specifically, we apply rf-radiation (MHz) to a quadrupole magnetic field, which results in an ellipsoidal trapping potential for rubidium-87 atoms in the F=1 manifold. This geometry is time-averaged with the help of oscillating (kHz) Helmholtz fields. We develop a convenient loading scheme for the TAAP which uses a standard TOP trap and suffers negligible atom losses and heating. Subsequently we characterize the TAAP trap itself and observe low heating rates and sufficient lifetimes (>3s). Furthermore it is possible to use a second, weaker rf-field to evaporatively cool the atoms to quantum degeneracy [Phys. Rev. A. 81, 031402 (2010)]. This opens up a route for further experiments in this potential: we show how atoms can be trapped in a double well potential and a ring trap geometry. Additionally a process to instigate rotation in these potentials by rotating the polarization of the rf-radiation is developed and implemented. This allows us to impart angular momentum onto the atomic cloud and spin it into a ring.
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Dutta, Omjyoti. "Ground State Properties and Applications of Dipolar Ultracold Gases." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195700.
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This thesis contains a study of ultracold paramagnetic atoms or polar molecules characterized by a long-range anisotropic dipolar interaction. We particularly focus on two aspects of ultracold dipolar gases. In the first problem the ground state properties of dipolar Bose-Einstein condensates (BEC) are investigated. This problem has gained importance due to recent experimental advances in achieving a condensate of Chromium atoms and ongoing research to produce quantum degenerate polar molecules. In the second problem, we consider possible applications of ultracold polar molecules to rotation sensing and interferometry. First, we concentrate on the interplay between the trapping geometry and dipole-dipole interaction for a polarized dipolar bosonic condensate. As the dipole-dipole interaction is attractive along the polarized direction, the lowest energy state of the BEC is always a collapsed state. However by applying a trapping potential along the polarization direction it is possible to achieve a metastable dipolar BEC. By numerically solving the Gross-Pitaevskii equation, we show that below a critical interaction strength, a metastable state exists depending on the trapping geometry. We also show that a novel feature of dipolar BEC is the appearance of different structural metastable ground states for certain combinations of trapping geometry and particle number. Next, by mixing in single component fermions we show that dipolar BEC can be stabilized against collapse in pancake shaped or cylindrical traps. We also show that the excitation spectrum of the BEC may have a minimum for non-zero momentum, termed a “roton minimum”. This minimum leads to a transition to stable or metastable density-wave states depending on the density of the bosons and boson-fermion interaction strength. In the second problem, we study a proposal for a large-angle coherent beam splitter for polar molecules. By taking into account the effect of a quasi-static external electric field on the rotational levels of the polarized molecules we show that it is possible to coherently split a stationary cloud of molecules into two counter-propagating components. We then investigate the effect of longitudinal acceleration on the transverse motion of the particles, assuming that the longitudinal motion of the molecules can be approximated classically by a wave packet with some mean velocity while the transverse motion is governed by quantum mechanics. We propose a particular time-dependent shape of acceleration to minimize the excitations in the transverse motion. Our theory is also applicable to the general case of particles moving along a circular guide with time-dependent longitudinal velocity. In addition, we include the effects of velocity fluctuations due to noise in the accelerating field.
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Park, Jee Woo. "An ultracold gas of dipolar fermionic ²³Na⁴⁰K molecules." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104529.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 190-202).
In this thesis, I present my work on creating ultracold dipolar molecules of ²³Na⁴⁰K in the singlet rovibrational ground state. These fermionic molecules have a large permanent electric dipole moment of 2.72 Debye, and are chemically stable against inelastic dimer-dimer reactions. A quantum gas of these molecules have potential applications in quantum simulation of novel dipolar many-body physics, creation of dipolar quantum matter, precision measurements of fundamental constants, and quantum information processing. The work starts with the creation of a new Bose-Fermi mixture of ²³Na and ⁴⁰K, and a systematic study of Feshbach resonances between the two atomic species. The study reveals more than 20 resonances in the s- and p-wave collision channels, and many of the s-wave resonances are exceptionally broad. Using two distinct s-wave resonances, we create loosely bound Feshbach molecules of ²³Na⁴⁰K, which serve as a stepping stone for the creation of more deeply bound molecules. To transfer Feshbach molecules to the singlet rovibrational ground state, molecular spectroscopy is performed in search of a suitable two-photon pathway. We find two excited molecular states with with strong coupling to the Feshbach molecular state and the singlet rovibrational ground state. One of the two pathways is used to create ²³Na⁴⁰K singlet rovibrational ground state molecules by stimulated Raman adiabatic passage (STIRAP). The created molecular gas has T/TF ~~ 2.0, and exhibits trap lifetimes longer than 2.5 seconds, highlighting NaK's chemical stability. Coherent microwave control of rotational and hyperfine states of ²³Na⁴⁰K ground state molecules is demonstrated. In particular, we observe long coherence times of the molecular sample approaching one second in a superposition of two hyperfine levels in the singlet rovibrational ground state. The long coherence time allows precision spectroscopy of the molecular gas, which we use to detect Hz-level shifts between the hyperfine levels.
by Jee Woo Park.
Ph. D.
25
Rvachov, Timur Michael. "Ultracold ²³Na⁶Li molecules in the triplet ground state." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119113.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 161-173).
This thesis describes experiments in spectroscopy and formation of triplet ²³Na⁶Li molecules from an initial mixture of ultracold ²³Na and ⁶Li. The production of quantum degenerate molecules with long-range dipolar interactions is a long-standing goal in low temperature physics. NaLi is a fermionic molecule with an electric dipole moment of 0.2 Debye and a magnetic dipole moment of 2 [mu]B in its triplet ro-vibrational ground state. The formation of an ultracold molecule with both electric and magnetic dipole moments allows for novel opportunities in control of ultracold molecular reactions and studies of quantum many-body systems with dipolar interactions. This experimental work consists of two parts. The first is a thorough spectroscopic study of the excited and ground triplet potentials of NaLi using one- and two-photon photoassociation spectroscopy. We present the spectroscopic positions and strengths of transitions to nearly all vibrational states in the excited c³[sigma]⁺ and ground ³[sigma]⁺ potentials of NaLi. This is the first spectroscopic observation of triplet potentials in NaLi and the first demonstration of photoassociation in the Na-Li system. The second part utilizes our spectroscopic results to coherently form an ultracold gas of NaLi molecules. Starting with an ultracold Na-Li mixture, we use magneto-association to form weakly bound Feshbach molecules. The Feshbach molecules are then transfered to the ro-vibrational triplet ground state using a two-photon stimulated Raman adiabatic passage (STIRAP) technique, forming 3 x 10⁴ molecules at a density of 5 x 10¹⁰ cm⁻³ and temperature of 3 [mu]K. The molecules are long-lived with a measured lifetime of 5 seconds, which highlights their fermionic nature and low universal inelastic loss rate. The utility of the molecule's magnetic moment is demonstrated by performing electron spin resonance spectroscopy to measure the hyperfine structure of the molecule.
by Timur Michael Rvachov.
Ph. D.
26
Yan, Zoe Z. (Zoe Ziyue). "From strongly-interacting Bose-Fermi mixtures to ultracold molecules." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/130219.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, May, 2020Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 193-213).
This thesis describes experiments on ultracold quantum gases. First, I discuss quantum simulation involving mixtures of bosonic and fermionic atoms. Second, I present work on creating and controlling ultracold dipolar molecules of ²³Na⁴⁰K. The rich phase diagram of Bose-Fermi mixtures was studied with our system of bosonic ²³Na and fermionic ⁴⁰K atoms. When the fermions were immersed as a minority species within a Bose-Einstein condensate, the system realized the canonical Bose polaron quasiparticle, which is an important paradigm in condensed matter physics. We investigated the strongly-coupled Bose polaron as it approached the quantum critical regime of the Bose-Fermi mixture. Using radiofrequency spectroscopy, we probed the binding energy and decay rate as a function of temperature.
In particular, the decay rate was found to scale linearly with temperature near the Planckian rate k[subscript B]T/h⁻ in the unitarity-limited regime, a hallmark of quantum critical behavior. Bose-Fermi mixtures host a complex spectrum of collective excitations, which can shed light on their properties such as collisional relaxation rates, equilibrium equations of state, and kinetic coefficients. We probed the low-lying collective modes of a Bose-Fermi mixture across different interaction strengths and temperatures. The spin-polarized fermions were observed to transition from ballistic to hydrodynamic flow induced by interactions with the bosonic excitations. Our measurements establish Bose-Fermi mixtures as a fruitful arena to understand hydrodynamics of fermions, with important connections to electron hydrodynamics in strongly-correlated 2D materials. The second part of this thesis describes the creation and manipulation of ultracold molecules in their ground state.
Molecules have more tunable degrees of freedom compared to atoms, paving the way for studies of quantum state-controlled chemistry, quantum information, and exotic phases of matter. We created loosely-bound Feshbach molecules from ultracold atoms, then transferred those molecules to their absolute electronic, vibrational, rotational, and hyperfine ground state by stimulated Raman adiabatic passage. The rotational level structure, sample lifetimes, and coherence properties were studied, culminating in a demonstration of second-scale nuclear spin coherence times in an ensemble of NaK. Controlling the intermolecular interactions - which can be tunable, anisotropic, and long range - is an outstanding challenge for our field. We induced strong dipolar interactions via the technique of microwave dressing, an alternative to using static electric fields to polarize the molecules.
The origin of these dipolar collisions was the resonant alignment of the approaching molecules' dipoles along their intermolecular axis, resulting in strong attraction. Our observations were explained by a conceptually simple two-state picture based on the Condon approximation.
by Zoe Z. Yan.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics
27
Li, Junru Ph D. Massachusetts Institute of Technology. "Spin-orbit coupling and supersolidity in ultracold quantum gases." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123348.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 207-214).
Ultracold quantum gases provide a clean, isolated, and controllable platform for simulating and characterizing complex physical phenomena. In this thesis, I present several experiments on realizing one-dimensional spin-orbit coupling in ultracold 23Na gases and the creation of a new form of matter with supersolid properties using interacting spin-orbit coupled Bose-Einstein condensates. The first part describes the realization of spin-orbit coupling in optical superlattices which consist of stack of pancakes of imbalanced double-wells. The orbital levels, individual pancakes, in an superlattice potential are used as pseudospin states. Spinorbit coupling was induced by two-photon Raman transition between the pseudospin states, and was experimentally characterized by the spin-dependent momentum structure from this dressing. The realization suppresses heating due to spontaneous emission.
The system is highly miscible, allowing the study of novel phases in interacting spin-orbit coupled systems. Next, spin-orbit coupling was demonstrated by synchronizing a fast periodically modulating magnetic force with the Radio-Frequency (RF) pulses. The modulation effectively dressed the RF photons with tunable momentum. The consequent Doppler shifts for RF transitions were observed as velocity-selective spin flips. The scheme is equivalent to Floquet engineered one-dimensional spin-orbit coupling. Finally, I report experiments on creating a new form of matter, a supersolid, in ultracold quantum gases. An interacting spin-orbit coupled Bose-Einstein condensate in the stripe phase spontaneously breaks two continuous symmetries : the U(1) symmetry, observed as sharp interference peaks in momentum space, and the continuous translational symmetry, observed as a spontaneously formed density modulation. The density modulation is measured and characterized with Bragg scattering.
A system spontaneously breaking these two symmetries is a crystal and a superfluid simultaneously, and is considered as a supersolid.
by Junru Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics
28
Lyon, Mary Elizabeth. "Towards Stronger Coulomb Coupling in an Ultracold Neutral Plasma." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4194.
Full textAbstract:
Ultracold neutral plasmas are created by photoionizing laser-cooled atoms in a magneto-optical trap (MOT). Due to their large electrical potential energies and comparatively small kinetic energies, ultracold plasmas fall into a regime of plasma systems which are called “strongly coupled.” A priority in the field of ultracold plasmas is to generate plasmas with higher values of the strong coupling parameter Γ, which is given as the ratio of the nearest-neighbor Coulomb potential energy to the average kinetic energy. The equilibrium strong coupling in ultracold plasmas is limited by the ultrafast relaxation of the ions due to spatial disorder in the initial system. This heating mechanism is called “disorder-induced heating” (DIH) and it limits the ion strong coupling in ultracold plasmas to order unity. This thesis describes experiments that explore ways to generate higher values of the strong coupling parameter in an ultracold neutral calcium plasma.One way to increase Γ is to mitigate the effects of DIH using electron screening. This thesis describes an experiment in which the initial electron temperature was systematically changed to determine the effect that electron screening has on the ion thermalization. At lower initial electron temperatures, corresponding to a higher degree of electron shielding, it was found that the screening slows the ion thermalization and reduces the equilibrium ion temperature by as much as a factor of two. However, electron screening also reduces the ion interaction strength by the same amount, which has the net effect of leaving the effective Γ unchanged.Another method for increasing the strong coupling of an ultracold plasma is to excite the plasma ions to a higher ionization state. Simulations predict that doubly ionizing the plasma ions can increase the strong coupling in an ultracold plasma by as much as a factor of 4, with the maximum value of Γ depending on the timing of the second ionization relative to the DIH process. This thesis describes an experiment designed to test these predictions in a Ca2+ plasma. Measurements of the change in the Ca+ ion temperature as a function of the timing of the second ionization pulses were made using laser-induced fluorescence. Results of these measurements show that the heating of the Ca+ ions due to the second ionization depends on the timing of the second ionization pulses, as predicted by MD simulations.
29
Liu, Ivan Chen-Hsiu. "Ultracold Rydberg Atoms in Structured and Disordered Environments." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1231945394343-32656.
Full textAbstract:
The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.
30
Medley, Patrick (Patrick M. ). "Thermometry and cooling of ultracold atoms in an optical lattice." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/68977.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 127-132).
Ultracold atoms of 7Rb were prepared in a mixture of two hyperfine states, F 1, mF = -1 > and 2, -2 >. This two-component system was then studied in the presence of a magnetic field gradient and an optical lattice. The presence of a magnetic field gradient separated the atoms into regions of opposite spin, with a boundary region of mixed spin in the center. In the presence of an optical lattice, the width of this region was found to be proportional to the system's temperature and inversely proportional to the strength of the magnetic field. This allowed the measurement of the size of the boundary region to act as a thermometer for the system, representing the first demonstration of spin gradient thermometry. This thermometer represents the first practical method for thermometry in the Mott insulator, and has features of high dynamic range and tunable sensitivity. Given sufficient optical resolution and control over the magnetic field gradient, the lower limit of this thermometer is set by quantum magnetic ordering effects. The dynamic response of this system to changes in magnetic field gradient was studied, both in the weak and strong lattice regimes. The result of these studies was the development of spin gradient demagnetization cooling. By performing an adiabatic drop in gradient strength while still in the superfluid, significant cooling of the entire system was observed. When the same process was performed in the Mott insulator, the spin temperature was cooled dramatically, while remaining out of equilibrium with the remaining degrees of freedom of the system. By reversing the gradient direction, inverted spin populations with negative temperatures have been produced. Spin gradient demagnetization has produced the closest approach to absolute zero yet recorded: 300 pK for the equilibrated system, and spin temperatures of 75 pK as well as -75 pK. The ability to achieve these temperatures puts studies of quantum magnetism in optical lattices within reach.
by Patrick Medley.
Ph.D.
31
Campbell, Sara L. S. B. Massachusetts Institute of Technology. "Building an apparatus for ultracold lithium-potassium Fermi-Fermi mixtures." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61204.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 93-95).
In this thesis, I designed and built laser systems to cool, trap and image lithium-6 and potassium-40 atoms. I also constructed the vacuum system for the experiment and experimentally tested a new method to coat the chamber with a Titanium-Zirconium- Vanadium alloy that acts as a pump. The final apparatus will use a 2D Magneto- Optical Trap (MOT) as a source of cool potassium and a Zeeman slower as a source of cool lithium. The atoms will then be trapped and cooled together in a double-species 3D MOT. In the 3D MOT, we will perform photoassociation spectroscopy on the atoms to determine the Li-K molecular energies and collisional properties. Using this information, we can transfer weakly-bound Feshbach LiK molecules into their ground state. LiK has an electric dipole moment and will open the door to the study of novel materials with very long-range interactions. This new material might form a crystal, a superfluid with anisotropic order parameter or a supersolid.
by Sara L. Campbell.
S.B.
32
Kennedy, Colin (Colin Joseph). "Creating novel quantum states of ultracold bosons in optical lattices." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112076.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 249-263).
Ultracold atoms in optical lattices are among the most developed platforms of interest for building quantum devices suitable for quantum simulation and quantum computation. Ultracold trapped atoms are advantageous because they are fundamentally indistinguishable qubits that can be prepared with high fidelity in well-defined states and read-out with similarly high fidelities. However, an outstanding challenge for ultracold atoms in optical lattices is to engineer interesting interactions and control the effects of heating that couple the system to states that lie outside the Hilbert space we wish to engineer. In this thesis, I describe a series of experiments and theoretical proposals that address several critical issues facing ultracold atoms in optical lattices. First, I describe experiments where the tunneling behavior of atoms in the lattice is modified to make our fundamentally neutral particles behave as though they are charged particles in a magnetic field. We show how engineering this interaction creates intrinsic degeneracy in the single particle spectrum of the many-body system and how to introduce strong interactions in the system with the goal of producing exotic many-body states such as a bosonic fractional quantum Hall states. Then, I discuss how this technique can be easily generalized to include spin and higher spatial dimensions in order to access a rich variety of new physics phenomena. Next, I report on the realization of a spin-1 Heisenberg Hamiltonian which emerges as the low energy effective theory describing spin ordering in the doubly-occupied Mott insulator of two spin components. This integer spin Heisenberg model is qualitatively different from the half-integer spin model because it contains a gapped, spin-insulating ground state for small inter-spin interaction energies which we call the spin Mott. Using a spin-dependent lattice to control the inter-spin interactions, we demonstrate high-fidelity, reversible loading of the spin-Mott phase and develop a probe of local spin correlations in order to demonstrate a spin entropy below 0.2 kB per spin. Progress on adiabatically driving the quantum phase transition from the spin Mott to the xy-ferromagnetic is discussed along with the progress towards the creation of a quantum gas microscope for single atom detection and manipulation..
by Colin Kennedy.
Ph. D.
33
Burton, William Cody. "Ultracold bosons in optical lattices for quantum measurement and simulation." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123353.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 131-139).
Ultracold atoms provide a platform that allows for pristine control of a physical system, and have found uses in both the fields of quantum measurement and quantum simulation. Optical lattices, created by the AC Stark shift of a coherent laser beam, are a versatile tool to control ultracold atoms and implement novel Hamiltonians. In this thesis, I report on three experiments using the bosonic species Rubidium-87 trapped in optical lattices. I first discuss our work in simulating the Harper-Hofstadter Hamiltonian, which describes charged particles in high magnetic fields, and has connections to topological physics. To simulate the charged particles, we use laser-assisted tunneling to add a complex phase to tunneling in the optical lattice. For the first time, we have condensed bosons into the ground state of the Harper-Hofstadter Hamiltonian.
In addition, we have demonstrated that we can add strong on-site interactions to the effective Hamiltonian, opening the door to studies of interesting states near the Mott insulator transition. Next, I present a novel technique to preserve phase coherence between separated quantum systems, called superfluid shielding. Phase coherence is important for both quantum measurement and simulation, and is fundamentally limited by projection noise. When an interacting quantum system is split, frozen-in number fluctuations lead to fluctuations of the relative phase between separated subsystems. We cancel the effect of these fluctuations by immersing the separated subsystems in a common superfluid bath, and demonstrate that we can increase coherence lifetime beyond the projection noise limit. Finally, I discuss our efforts in simulating magnetic ordering in the spin-1 Heisen- berg Hamiltonian.
It is hard to adiabatically ramp into magnetically ordered ground states, because they often have gapless excitations. Instead, we use a spin-dependent lattice to modify interspin interactions, allowing us to ramp into the spin Mott insulator, which has a gap and can therefore act as a cold starting point for exploration of the rest of the phase diagram. We have achieved a cold spin temperature in the spin Mott insulator, and I discuss plans to also achieve a cold charge temperature and then ramp to the the xy-ferromagnet, which has spin-charge separation.
by William Cody Burton.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics
34
Cole, William S. Jr. "Spin-orbit coupling and strong correlations in ultracold Bose gases." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406217577.
Full text
35
McCabe, David J. "The formation of ultracold rubidium molecules using ultrafast photoassociation." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:65e44f72-1995-45f0-8751-898735e54b6e.
Full textAbstract:
The establishment of robust laser-cooling techniques for the formation of ultracold atoms has provided a test-bed for low-temperature science, with scattering events changing character from incoherent thermal interactions to coherent quantum mechanical events. A natural extension is the pursuit of ultracold molecules in prescribed low-energy internal states. Atomic cooling techniques, however, do not generalize to the molecular regime due to the complex energy-level structure afforded by its extra degrees of motion. An indirect approach to ultracold molecule formation - photoassociation using ultrafast laser pulses - is the focus of this thesis. A broadband field associates atom pairs into a localized molecular wavepacket that evolves within the attractive excited-state potential. A suitably timed dump pulse may thus be applied to stabilize population into deeply bound ground vibrational states. This strategy may be generalized to any species whose spectroscopy matches the pulse spectrum, and offers a coherent population transfer scheme that does not require precise knowledge of the system. This thesis presents experiments using high-energy photoassociation pulses applied to ultracold rubidium atoms. The pulses quench the background ground-state molecular population but form bound dimers within the excited state. A pump-probe experiment was designed to chart the excited-state dynamics; however, the oscillations predicted by theoretical calculations were not evident in the molecular signal. The nature of the dynamics is expected to be strongly dependent on the initial state of the atom pairs addressed by the ultrafast pulse: a bound molecular population provides an additional candidate to free atoms. A spectroscopic measurement characterizes these bound molecules and identifies their formation mechanism. A subsequent experiment provides evidence that the predominant contributor to the pump-probe signal is the unbound initial population. The consequences with regard to both the observation of excited-state dynamics and the subsequent application of a dump pulse are discussed.
36
England, Duncan. "Towards ultrafast photoassociation of ultracold atoms." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:1e2a7450-e568-4f11-9c56-bb62250cd3df.
Full textAbstract:
In the ultracold regime, where the interactions between atoms become quantum mechanical in nature, we can investigate the fundamental properties of matter. A natural progression from the catalogue of pioneering experiments using ultracold atoms is to extend the size of our quantum system by producing ultracold molecules in prescribed low-energy internal states. Techniques for cold molecule production are split into two methods: direct and indirect cooling. While direct cooling methods have yet to realize ultracold temperatures, collisional relaxation in the molecules leads to low internal energy states. By contrast, indirect cooling — the association of molecules from pre-cooled atoms—has produced a range of molecules at ultracold temperatures; the challenge with this technique is to control the internal state. This thesis concentrates on a technique that is complementary to those already in existence: ultrafast photoassociation. Key to this technique is the formation of time non-stationary wavepackets in the excited-state in order to improve FranckCondon overlap of the excited state with deeply bound ground-state vibrational levels. A pump-probe experiment was designed and built to demonstrate the formation of bound excited-state dimers. In this work we show that the initial state from which the wavepacket originates is of critical importance to the evolution of excited-state population. We find that the internuclear separation of the wavepacket produced in a rubidium magneto-optical trap is too large to observe coherent oscillations in the excited state. The implications of this are discussed along with recommendations for future ultrafast photoassociation experiments. Consequently, a new ultracold atom apparatus was built utilizing magnetic and dipole-force trapping to increase the density of the atomic sample; this apparatus will enable future experiments combining the exciting fields of ultracold matter and ultrafast light.
37
Liu, Ivan Chen-Hsiu. "Ultracold Rydberg Atoms in Structured and Disordered Environments." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23624.
Full textAbstract:
The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.
38
Vant, Kendra Margaret Denny. "Spectroscopy of ultracold metastable hydrogen : in pursuit of a precision measurement." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34394.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 141-145).
This thesis describes the first observations in trapped hydrogen of optical transitions starting from the metastable 2S state. It covers in detail the design and construction of two stabilized diode laser systems for performing spectroscopy of the 2S-3P and 2S-8S transitions. Spectroscopy of the one photon 2S-3P transition in hydrogen is demonstrated both by the depletion of the metastable 2S atom state and the absorption of the 2S-3P laser light. A model for absorption spectroscopy as a probe for metastable number is developed and absorption is shown to offer a major improvement over current detection methods. In the course of these experiments, techniques with diode lasers were developed that will be used later in the proposed precision measurements of 2S-nS transitions. The design, construction and characterization of the diode laser system for performing spectroscopy of the two photon 2S-8S transition is explained and recommended parameters for a proposed signal search are outlined.
by Kendra Margaret Denny Vant.
Ph.D.
39
Bowman, David. "Ultracold atoms in flexible holographic traps." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16293.
Full textAbstract:
This thesis details the design, construction and characterisation of an ultracold atoms system, developed in conjunction with a flexible optical trapping scheme which utilises a Liquid Crystal Spatial Light Modulator (LC SLM). The ultracold atoms system uses a hybrid trap formed of a quadrupole magnetic field and a focused far-detuned laser beam to form a Bose-Einstein Condensate of 2×105 87Rb atoms. Cold atoms confined in several arbitrary optical trapping geometries are created by overlaying the LC SLM trap on to the hybrid trap, where a simple feedback process using the atomic distribution as a metric is shown to be capable of compensating for optical aberrations. Two novel methods for creating flexible optical traps with the LC SLM are also detailed, the first of which is a multi-wavelength technique which allows several wavelengths of light to be smoothly shaped and applied to the atoms. The second method uses a computationally-efficient minimisation algorithm to create light patterns which are constrained in both amplitude and phase, where the extra phase constraint was shown to be crucial for controlling propagation effects of the LC SLM trapping beam.
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Li, Weiran. "Topics in Ultracold Atomic Gases: Strong Interactions and Quantum Hall Physics." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1375706577.
Full text
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Callahan, Nathan, Chen-Yu Liu, Fransisco Gonzalez, Evan Adamek, James D. Bowman, Leah J. Broussard, S. M. Clayton, et al. "Monte Carlo of Trapped Ultracold Neutrons in the UCNτ Trap." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/5531.
Full textAbstract:
In the UCNτ experiment, ultracold neutrons (UCN) are confined by magnetic fields and the Earth’s gravitational field. Field-trapping mitigates the problem of UCN loss on material surfaces, which caused the largest correction in prior neutron experiments using material bottles. However, the neutron dynamics in field traps differ qualitatively from those in material bottles. In the latter case, neutrons bounce off material surfaces with significant diffusivity and the population quickly reaches a static spatial distribution with a density gradient induced by the gravitational potential. In contrast, the field-confined UCN—whose dynamics can be described by Hamiltonian mechanics—do not exhibit the stochastic behaviors typical of an ideal gas model as observed in material bottles. In this report, we will describe our efforts to simulate UCN trapping in the UCNτ magneto-gravitational trap. We compare the simulation output to the experimental results to determine the parameters of the neutron detector and the input neutron distribution. The tuned model is then used to understand the phase space evolution of neutrons observed in the UCNτ experiment. We will discuss the implications of chaotic dynamics on controlling the systematic effects, such as spectral cleaning and microphonic heating, for a successful UCN lifetime experiment to reach a 0.01% level of precision.
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Benjamin, David Isaiah. "Impurity Physics in Resonant X-Ray Scattering and Ultracold Atomic Gases." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13067679.
Full textAbstract:
This thesis presents work on theoretical tools used to study transient and quantum-fluctuating impurity potentials that arise in resonant x-ray scattering and ultracold atomic gases. These tools fall under two main classes, functional determinants for exact evaluation of many-fermion matrix elements, and the variational polaron transformation. The following work carefully introduces both approaches and compares theoretical predictions to known experimental and computational results. In several cases this thesis presents arguments that experiments on high-temperature superconducting cup rates must be reinterpreted in terms of a quasiparticle picture. Where no experimental data exist, predictions are made and suggestions given for new uses for simple experimental techniques. For example, indirect resonant inelastic x-ray scattering turns out to be a versatile pseudo gap probe, and radio frequency absorption of a fermi gas with an impurity can detect a repulsively-bound state.Physics
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Cooper, Nathan. "Novel techniques for the trapping and manipulation of ultracold atoms." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/368606/.
Full textAbstract:
We describe several novel techniques for the optical trapping of ultracold atoms and for the production of wavelength-stabilised, coherent light at the frequencies required for use in atomic physics experiments. The greater part of this thesis deals with work towards the creation of regular arrays of microscopic optical dipole traps formed at the foci of truncated spherical cavities in a metallic film, in which the inter-site spacing can be set anywhere between one and several hundred micrometers. Arrays of such cavities are synthesised and structurally characterised via optical and electron microscopy, and numerical simulations of the light intensity distribution near the foci of such cavities under normal illumination are used to confirm their suitability for dipole trap production. A method for the construction of arrays of magneto-optical traps based on such structures is proposed and theoretically examined, and some preliminary experimental work towards the synthesis of the required microstructures is also described. Possible approaches to the loading of such traps and the imaging of the atoms contained therein are discussed - experimental work towards ballistic atom transfer from a specialised form of magneto-optical trap that can be formed close to a microstructured surface is carried out, and the efficacy of wavelength-selective fluorescence imaging as a means of reducing the effects of background scatter from the surface is experimentally demonstrated. Further work described herein includes the proposal and experimental demonstration of two novel techniques for the removal of the carrier wave from a phase-modulated laser beam, one of which is based on a fiber-optic Mach-Zehnder interferometer that is shown to be an effective device for splitting or combining beams of nearly equal frequencies. A spontaneous-force based atom trapping mechanism that does not rely on the use of a magnetic field, but rather on spatially-dependent optical pumping between different metastable atomic states, is also proposed, and a proof of principle experiment is carried out to demonstrate the validity of the suggested mechanism. We find that this trapping scheme allows the spatial dependence of the trapping force to be tailored with a greater degree of exibility than is usually possible with magneto-optical trapping, and that it is also capable of producing traps with stronger spring constants than are typically achievable with magneto-optical trapping under realistic experimental constraints.
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Akyar, Ozge. "Density Functional Theory For Trapped Ultracold Fermions." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610948/index.pdf.
Full textAbstract:
Recently a new outlook on dealing with dipolar ultracold fermions based on density
functional methods has received attention. A Thomas-Fermi treatment coupled with
a variational approach has been developed for a collection of fermions trapped in a
harmonic potential interacting via dipole-dipole forces. In this thesis, firstly our alternative
formalism for Thomas-Fermi method by performing some calculations based
on the Kohn-Sham formalism which is one of the main idea of density functional theory
is investigated. Furthermore, density distributions are obtained dependent to the
parametersrescaled interaction strength, dipole-dipole energy and the trap parameter which determine the trap geometry based on this theory. The thesis starts with a brief outline of the density functional theory and theory of our system, continues with calculations based on this theory, which are free of any variational assumptions for the density profile. Moreover, results of density graphics for harmonic trap will be followed by discussion of comparison and contrast with Thomas-Fermi method based on the paper of Goral et al.. These discussions are mainly about the shape of the density distribution, variation of the cloud parameters and energy behaviours according to the rescaled interaction strength. The thesis concludes with an analysis of contribution of density functional theory to this fermionic system.
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Douglas, James Stewart. "Light scattering from ultracold atomic gases." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:0aa4ede3-8b6e-45d4-a112-a2d18271307c.
Full textAbstract:
Systems of ultracold atoms in optical potentials have taken a place at the forefront of research into many-body atomic systems because of the clean experimental environment they exist in and the tunability of the system parameters. In this thesis we study how light scattered from these ultracold atomic gases reveals information about the state of the atomic gas and also leads to changes in that state. We begin by investigating the angular dependence of light scattered from atoms in optical lattices at finite temperature. We demonstrate how correlations in the superfluid and Mott insulator states affect the scattering pattern, and we show that temperature affects the number of photons scattered. This effect could be used to measure the temperature of the gas, however, we show that when the lattice band structure is taken into account the efficiency of this temperature measurement is reduced. We then investigate light scattering from small optical lattices where the Bose-Hubbard Hamiltonian can be solved exactly. For small lattices, scattering a photon from the atomic system significantly perturbs the atomic system. We develop a model of the evolution of the many-body state that results from the consecutive scattering and detection of photons. This model shows that light scattering pushes the system towards eigenstates of the light scattering measurement process, in some cases leading to a superposition of atomic states. In the second half of this thesis we study light scattering that depends on the internal hyperfine spin state of the atoms, in which case the scattered light can form images of the spatial atomic spin distribution. We demonstrate how scattering spatially correlated light from the atoms can result in spin state images with enhanced spatial resolution. We also show how using spatially correlated light can lead to direct measurement of the spatial correlations of the atomic spin distribution. We then apply this theory of spin-dependent light scattering to the detection of different spin states of ultracold gases in synthetic magnetic fields. We show that it is possible to distinguish between ground states in the quantum Hall regime using light scattering. Moreover, we show how noise correlation analysis of the spin state images can be used to identify the correlations between atoms and how a variant on phase-contrast imaging can reveal the relationship between the atomic spins.
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Harte, Tiffany. "Ultracold atoms in dressed potentials." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:1a4ea098-ec17-414a-8873-95d83ca8ea97.
Full textAbstract:
Time-varying fields are widely used to extend the accessible range of trapping potentials for ultracold atoms. This work explores two very different examples of such fields, in the radiofrequency and optical regimes, whose interactions with trapped atoms can both be described in terms of the dressed atom picture. Forming the basis of this work are radiofrequency dressed adiabatic potentials based on macroscopic trapping coils. Atoms are confined at the south pole of the resultant oblate spheroidal trapping surfaces. This work describes the extension of these potentials by two different methods: the application of multiple dressing radiofrequencies, and addition of a rapidly-scanned optical dipole trap. This is the first experimental demonstration of a multiple-radiofrequency dressed adiabatic potential, explored using ultracold 87Rb atoms confined in a highly configurable double well. Due to the independent generation of each constituent dressing frequency, the depth of each trapping well and the height of the barrier are easily manipulated, enabling precise and reliable transfer of atoms between the available trapping geometries. Experimental work includes an exploration of the potential-shaping capabilities of the three-radiofrequency system, and characterisation of the potential landscape using radiofrequency spectroscopy with good agreement to the eigenvalues numerically calculated using Floquet theory. This initial exploration of multiple-radiofrequency techniques lays the groundwork for applications in studying double well physics in a two-dimensional system, and independent state or species selective manipulation of trapped atoms. The potential shaping capabilities of this method can also be extended by applying additional trapping frequencies. In a supplementary line of experimental work, an optical dipole trapping system has been constructed, and the trapping beam aligned to the lower surface of the radiofrequency dressed trapping shell in order to sculpt the radial confinement. Beam shaping is achieved using an acousto-optic deflector, which can be used to produce either a composite array of static deflected beams, a rapidly-scanned painted potential, or some combination of the two approaches. The development and extension of the experimental apparatus required to implement these enhanced dressed state potentials is explored, and the challenges of their experimental implementation considered.
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Jo, Gyu-Boong. "Quantum coherence and magnetism in bosonic and fermionic gases of ultracold atoms." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/63010.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 168-185).
In this thesis, two sets of experimental studies in bosonic and fermionic gases are described. In the first part of the thesis, itinerant ferromagnetism was studied in a strongly interacting Fermi gas of ultracold atoms. The observation of nonmonotonic behavior of lifetime, kinetic energy, and size for increasing repulsive interactions provides strong evidence for a phase transition to a ferromagnetic state. Our observations imply that itinerant ferromagnetism of delocalized fermions is possible without lattice and band structure, and our data validate the most basic model for ferromagnetism introduced by Stoner. In the second part of the thesis, the coherence properties of a Bose-Einstein condensate (BEC) was studied in a radio frequency induced double-well potential implemented on a microfabricated atom chip. We observed phase coherence between the separated condensates for times up to 200 ms after splitting, a factor of 10 longer than the phase diffusion time expected for a coherent state for our experimental conditions. The enhanced coherence time is attributed to number squeezing of the initial state by a factor of 10. Furthermore, the effect of phase fluctuations on an atom interferometer was studied in an elongated BEC. We demonstrated that the atom interferometer using the condensates is robust against phase fluctuations; i.e., the relative phase of the split condensates is reproducible despite axial phase fluctuations. Finally, phase-sensitive recombination of two BECs was demonstrated on an atom chip. The recombination was shown to result in heating, caused by the dissipation of dark solitons, which depends on the relative phase of the two condensates. This heating reduces the number of condensate atoms and provides a robust way to read out the phase.
by Gyu-Boong Jo.
Ph.D.
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Steinberger, Julia K. 1974. "Progress towards high precision measurements on ultracold metastable hydrogen and trapping deuterium." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28649.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (leaves 128-136).
(cont.) not achieve deuterium trapping through helium-surface cooling. It is proposed that buffer gas loading can be used to cryogenically cool and trap deuterium.
Ultracold metastable trapped hydrogen can be used for precision measurements for comparison with QED calculations. In particular, Karshenboim and Ivanov [Eur. Phys. Jour. D 19, 13 (2002)] have proposed comparing the ground and first excited state hyperfine splittings of hydrogen as a high precision test of QED. An experiment to measure the 2S hyperfine splitting using a field-independent transition frequency in the 2S manifold of hydrogen is described. The relation between the transition frequency and the hyperfine splitting requires incorporating relativistic and bound state QED corrections to the electron and proton g-factors in the Breit-Rabi formula. Experimental methods for measuring the magnetic field of an ultracold hydrogen sample are developed for trap fields from 0 to 900 G. The temperature of the trapped sample at the field-independent point is a critical parameter, and is inferred from the IS - 2S lineshape. The detailed dependence of this lineshape on the trap geometry is examined. A search for the transition was undertaken, but no signal was observed. The systematics of the experiment are analyzed, and modifications for carrying out the experiment are proposed. In a separate study, the possibilities for trapping (never previously trapped) deuterium in the same cryogenic cell and magnetic trap used to trap hydrogen were investigated. Deuterium's behavior on a helium surface differs markedly from that of hydrogen due to its larger surface binding energy. We carried out a variety of studies of both hydrogen and deuterium during the trap-loading stage, working with both ⁴He and ³He surfaces. Introducing ³He in the cell decreases the surface binding energy of deuterium, and thus the rate of recombination on the cell walls; however, we could
by Julia K. Steinberger.
Ph.D.
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Yu, Ite Albert. "Ultracold surface collisions : sticking probability of atomic hydrogen on a superfluid 4He." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/44753.
Full text
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Santiago, González Ibon. "LiNaK : multi-species apparatus for the study of ultracold quantum degenerate mixtures." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77478.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 109-113).
This thesis describes the construction of a versatile apparatus to study ultracold quantum mixtures capable of simultaneously cooling fermionic ⁶Li and ⁴⁰K, as well as the bosonic ⁴¹K. The main features of the experimental setup are presented, in particular the addition of a new species ²³Na, which has enabled the study of the Bose-Fermi mixture ²³Na-⁴⁰K. Three main experimental benchmarks are outlined: first, the production of a Bose-Einstein Condensate of ⁴¹K is discussed and an evaluation of its properties as a coolant are analysed. Secondly, the creation of a triply degenerate Bose-Fermi-Fermi gas of ⁴¹K-⁴⁰K-⁶Li is presented. Simultaneous observation of Pauli Pressure and Bose Condensation in the triply degenerate gas is reported. In addition, interspecies Feshbach resonances between ⁴¹K-⁴⁰K and ⁶Li-⁴¹K are observed, opening the way to the study of a strongly interacting isotopic Bose-Fermi mixture of ⁴¹K-⁴⁰K, which have similar mass. Thirdly, the creation of a quantum degenerate Bose-Fermi mixture of ²³Na-⁴⁰K is discussed and over thirty Feshbach resonances are identified. Finally, a degenerate ²³Na-⁴⁰K Bose-Fermi mixture opens the way to creating fermionic NaK ground state molecules, which are known to be chemically stable and have a larger permanent electric dipole than KRb. This thesis concludes with a review of the molecular properties of NaK and explores the possibilities of bringing Feshbach molecules of NaK into the singlet rovibrational ground state.
by Ibon Santiago González.
S.M.