Quantum electronic transport in atomically layered topological insulators
Fatemi, Valla
The merger of topology and symmetry established a new foundation for understanding the physics of condensed matter, beginning with the notion of topological insulators (TIs) for electronic systems. For the time-reversal invariant TIs, a key aspect is the "helical" mode at the boundary of the system - that is, the ID edge of a 2D topological insulator or the 2D surface of a 3D topological insulator. These helical modes represent the extreme limit of spin-orbit coupling in that the spin-degenercy has been completely lifted while preserving time-reversal symmetry. This property is crucial for proposals realizing exotic excitations like the Majorana bound state. In this thesis, I present a series of experiments investigating electronic transport through the boundary modes of 3D and 2D topological insulators, specifically Bi1.5 Sb0.5 Te1.7 Se1.3 and monolayer WTe 2 , respectively. For the case of ultra-thin WTe 2 , I also present experiments detailing investigations of the 2D bulk states, finding a semimetallic state for the trilayer and a superconducting phase for the monolayer, both of which are strongly tunable by the electric field effect. The discovery of 2D topological insulator and 2D superconductor phases within the same material, accessible by standard solid state elecrostatic gates, places WTe2 in a unique situation among both TIs and superconductors, potentially enabling gate-configurable topological devices within a homogenous material platform.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 153-180).
Quantum electronic transport in atomically layered topological insulators
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Controlling ultracold fermions under a quantum gas microscope
Controlling ultracold fermions under a quantum gas microscope
Okan, Melih
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.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 123-130).
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Measurement of helium isotopic composition in cosmic rays with AMS-02
Measurement of helium isotopic composition in cosmic rays with AMS-02
Behlmann, Matthew Daniel
The isotopic composition of helium in cosmic ray fluxes provides valuable information about cosmic ray propagation through the Galaxy, which is of particular interest to indirect dark matter searches. Helium-3, mainly a secondary cosmic ray species, is primarily produced by spallation of heavier cosmic rays, such as primary helium-4, with interstellar matter. In six years of data taking, AMS has collected the largest available data set on fluxes of cosmic-ray helium. Events are selected to form a clean sample of galactic helium nuclei, for which velocity and rigidity give a measurement of particle mass that allows the measurement of relative isotope abundances. The resolution of measured mass is described in detail by template functions based on the underlying resolutions of the silicon tracker and ring-imaging Cerenkov detector measurements. This thesis presents a measurement of the cosmic ray helium isotope ratio 3 He/ 4He in the range 0.8-10 GeV/nucleon, as obtained through a template fitting approach on AMS data.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 137-145).
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Probing and preparing novel states of quantum degenerate rubidium atoms in optical lattices
Probing and preparing novel states of quantum degenerate rubidium atoms in optical lattices
Miyake, Hirokazu
Ultracold atoms in optical lattices are promising systems to realize and study novel quantum mechanical phases of matter with the control and precision offered by atomic physics. Towards this goal, as important as engineering new states of matter is the need to develop new techniques to probe these systems. I first describe our work on realizing Bragg scattering of infrared light from ultracold atoms in optical lattices. This is a detection technique which probes the spatial ordering of a crystalline system, and has led to our observation of Heisenberg limited wavefunction dynamics. Furthermore, we have observed the superfluid to Mott insulator transition through the matter wave Talbot effect. This technique will be particularly powerful for studying antiferromagnetic phases of matter due to its sensitivity to the crystalline composition. The second major component of this thesis describes a new scheme to realize the Harper Hamiltonian. The Harper Hamiltonian is a model system which effectively describes electrons in a solid immersed in a very high magnetic field. The effective magnetic field manifests itself as a position-dependent phase in the motion of the constituent particles, which can be related to gauge fields and has strong connections to topological properties of materials. We describe how we can engineer the Harper Hamiltonian in a two-dimensional optical lattice with neutral atoms by creating a linear potential tilt and inducing Raman transitions between localized states. In situ measurements provide evidence that we have successfully created the Harper Hamiltonian, but further evidence is needed to confirm the creation of the ground state of this Hamiltonian.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2013.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 137-146).
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The effects of light propagation in spherically symmetric metrics.
The effects of light propagation in spherically symmetric metrics.
Jaffe, Jack
Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1969. Ph.D.; Vita.; Bibliography: leaf 119.
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Trapping sodium with light
Trapping sodium with light
Raab, Eric Lowell
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1988.; Bibliography: leaves 177-182.
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Transient transport and contact effects in a-As₂Se₃
Transient transport and contact effects in a-As₂Se₃
Gibson, Dwight Deleno
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1986.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE; Bibliography: leaves 102-105.
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The ballast resistor : a simple dissipative structure.
The ballast resistor : a simple dissipative structure.
Ross, Benjamin Ira
Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept of Physics.; Microfiche copy available in Archives and Science.; Includes bibliographical references.
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Neutrinos, neurons and neutron stars : applications of new statistical and analysis techniques to particle and astrophysics
Neutrinos, neurons and neutron stars : applications of new statistical and analysis techniques to particle and astrophysics
Collin, Gabriel L.W.H
The IceCube detector opens a new window into our universe; valuable for both astronomy and particle physics. This thesis spans a wide range of topics that are bound together by a common theme: the development and application of new statistical and computational methods for analysing data from particle and astrophysics experiments. Sterile neutrinos are a hypothetical fourth kind of neutrino, which are motivated by anomalies observed in various short base-line neutrino experiments. These experiments have published results that are not mutually compatible. This thesis presents a global fit to many short base-line datasets with the addition of the recent IceCube sterile neutrino search, constraining the full 3+1 mixing matrix for the first time. The global fit strongly favours the sterile neutrino hypothesis, although significant tension still remains within the datasets. The origin of the observed astrophysical neutrino flux at IceCube remains elusive. Current methods, using a hot-spot model, have seen no significant clustering of events. This thesis presents a new test for point sources of neutrinos, based on the non-Poissonian Template Fitting technique. Constraints on population models for neutrino points sources are shown for the first time. Atmospheric neutrinos form a background for astrophysical analyses on IceCube, but also serve as the signal in particle physics analyses such as the sterile neutrino search. The first comprehensive study of the effect of global atmospheric temperature variations on atmospheric neutrino fluxes is provided. This thesis also presents two studies on using new computational methods for simulation and reconstruction on IceCube. Convolutional neural networks have been used to classify low-level waveform data, with the goal of identifying tau-neutrinos. Metropolis light transport, a rendering technique used in the CGI industry, has been extended to simulate the transport of light inside the IceCube experiment. Both show promising results, exceeding existing algorithms in their test cases.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages [181]-205) and index.
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Ultracold ²³Na⁶Li molecules in the triplet ground state
Ultracold ²³Na⁶Li molecules in the triplet ground state
Rvachov, Timur Michael
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.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 161-173).
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Aspects of highly-entangled quantum matter : from exotic phases, to quantum computation, and dynamics
Aspects of highly-entangled quantum matter : from exotic phases, to quantum computation, and dynamics
Vijay, Ksheerasagar
We explore three incarnations of highly-entangled quantum matter: as descriptions of exotic, gapped phases in three spatial dimensions, as resources for fault-tolerant quantum computation, and as the by-product of the unitary evolution of a quantum state, on its approach to equilibrium. In Part 1, we study quantum information processing in platforms hosting Majorana zero modes. We demonstrate that certain highly-entangled states may be engineered in arrays of mesoscopic topological superconducting islands, and used for fault-tolerant quantum computation. We then discuss measurement-based protocols for braiding Majorana zero modes and detecting their non-Abelian statistics in on-going experiments on proximitized, semiconductor nanowires, before proposing new families of error-correcting codes for fermionic qubits, along with concrete realizations. In Part 11, we study gapped, three-dimensional phases of matter with sub-extensive topological degeneracy, and immobile point-like excitations - termed "fractons" - which cannot be moved without nucleating other excitations. We find two broad classes of fracton phases in which (i) composites of fractons form topological excitations with reduced mobility, or (ii) all topological excitations are strictly immobile. We demonstrate a duality between these phases and interacting systems with global symmetries along sub-systems, and use this to find new fracton phases, one of which may also be obtained by coupling an isotropic array of two-dimensional states with Z₂ topological order. We introduce a solvable model in which the fracton excitations are shown to carry a protected internal degeneracy, which provides a generalization of non-Abelian anyons in three spatial dimensions. In Part III, we investigate the dynamics of operator spreading and entanglement growth in quantum circuits composed of random, local unitary operators. We relate quantities averaged over realizations of the circuit, such as the purity of a sub-system and the out-of-time-ordered commutator of spatially-separated operators, to a fictitious, classical Markov process, which yields exact results for the evolution of these quantities in various spatial dimensions. Operator spreading is ballistic, with a front that broadens as a dimension-dependent power-law in time. In this setting, we also map the dynamics of entanglement growth in one dimension to the stochastic growth of an interface and to the Kardar-Parisi-Zhang equation, which leads to a description of entanglement dynamics in terms of an evolving "minimal cut" through the quantum circuit, and provides heuristics for entanglement growth in higher-dimensions. The material presented here is based on Ref. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. Ref. [11, 12] are not discussed in this thesis, but were completed during my time at MIT.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 307-321).
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Quantum enhanced sensing and communication
Quantum enhanced sensing and communication
Zhuang, Quntao
Quantum phenomena such as entanglement and superposition enable performance beyond what classical physics can provide in tasks of computing, communication and sensing. Quantum sensing aims to enhance the measurement precision in parameter estimation or error probability in hypothesis testing. The first part of this thesis focuses on protocols for entanglement-enhanced sensing. However, various quantum sensing schemes' quantum advantage disappears in presence of decoherence from noise and loss. The quantum illumination protocol, on the other hand, has advantage over classical illumination even in presence of decoherence. This thesis provides the optimum receiver design for quantum illumination, and extends quantum illumination target detection to the realistic scenario with target fading and the Neyman-Pearson decision criterion. Quantum algorithms can solve difficult problems more efficiently than classical algorithms, which makes various classical encryption schemes vulnerable. To remedy this security issue, quantum key distribution enables sharing of secret keys with unconditional protocol security. However, the secret-key-rate of the state-of-art single-mode based quantum key distribution protocols are limited by a fundamental rate-loss trade-off. To enhance the secret-key-rate, this thesis proposes a multi-mode based quantum key distribution protocol. To prove its security, the noisy entanglement assisted classical capacity is developed to enable a security framework for two-way quantum key distribution protocols such as the one proposed here. An essential notion in the entanglement assisted capacity is additivity. This thesis constructs a channel with non-additive classical capacity assisted by limited entanglement assistance, even when the classical capacity of the channel is additive.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references.
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Classification of base geometries in F-theory
Classification of base geometries in F-theory
Wang, Yinan, Ph. D. Massachusetts Institute of Technology
F-theory is a powerful geometric framework to describe strongly coupled type JIB supcrstring theory. After we compactify F-theory on elliptically fibered Calabi-Yau manifolds of various dimensions, we produce a large number of minimal supergravity models in six or four spacetime dimensions. In this thesis, I will describe a current classification program of these elliptic Calabi-Yau manifolds. Specifically, I will be focusing on the part of classifying complex base manifolds of these elliptic fibrations. Besides the usual algebraic geometric description of these base manifolds, F-theory provides a physical language to characterize them as well. One of the most important physical feature of the bases is called the "non-Higgsable gauge groups", which is the minimal gauge group in the low energy supergravity model for any elliptic fibration on a specific base. I will present the general classification program of complex base surfaces and threefolds using algebraic geometry machinery and the language of non- Higgsable gauge groups. While the complex base surfaces can be completely classified in principle, the zoo of generic complex threefolds is not well understood. However, I will present an exploration of the subset of toric threefold bases. I will also describe examples of base manifolds with non-Higgsable U(1)s, which lead to supergravity models in four and six dimensions with a U(1) gauge group but no massless charged matter.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 187-196).
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Energy level structure of atoms in magnetic fields
Energy level structure of atoms in magnetic fields
Iu, Chun-Ho
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1991.; Includes bibliographical references (leaves 155-162).
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Nucleon structure and Its modification in nuclei
Nucleon structure and Its modification in nuclei
Schmookler, Barak (Barak A.)
Inclusive electron scattering experiments using fixed targets are an important tool for studying the structure of the nucleons. The electromagnetic structure of the proton, as encapsulated by its elastic form factors, can be extracted through measurements of the elastic electron-proton scattering cross-section. The GMp experiment in Hall A at the Thomas Jefferson National Accelerator Facility (JLab) seeks to measure this cross-section with high precision up to large momentum transfers. In addition, it is known that the inelastic structure of the nucleon is modified inside the nucleus. This modification, known as the EMC effect, can be studied using inclusive electron Deep Inelastic Scattering (DIS) on a nuclear target. Evidence suggests that the EMC effect may arise due to nucleon Short Range Correlations (SRC). This thesis describes studies of the elastic proton form factor measured in the GMp experiment at Hall A of JLab and studies of the EMC effect in nuclei relative to deuterium using data collected at the CLAS detector in Hall B at JLab. Furthermore, this works presents new measurements of SRC pair abundances in nuclei and develops a data-driven SRCbased phenomenological model of the EMC effect, which can correctly describe the effect across nuclei.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 181-184).
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Introducing spin-orbit interaction in graphene
Introducing spin-orbit interaction in graphene
Khoo, Jun Yong
The excellent electron properties of graphene, an atomically-thin material with record-high carrier mobility and gate tunability, make it central to modern nanoscience. However, the spin-orbit interaction (SOI) naturally present in graphene is extremely weak and has yet to be observed experimentally. This presents an obstacle for accessing novel phenomena in transport and optics, in particular those related to topological properties. This thesis seeks to address this limitation by artificially introducing SOI in graphene sandwiched between other atomically-thin materials that can produce an interfacial SOI in graphene. In particular, it is demonstrated that a strong SOI, naturally present in the two-dimensional materials such as transition metal dichalcogenides (TMD), can be partially transferred to graphene via the proximity effect. We predict a range of novel phenomena arising in graphene bilayers with layer-asymmetric SOI induced by a proximal TMD layer. These include a gate-tunable SOI, a gate-tunable intrinsic valley-Hall conductivity, as well as a gate-tunable edge conductivity, to name just a few. These findings will facilitate exploring previously inaccessible spin-related phenomena in graphene and other van der Waals heterostructures.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 131-146).
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Novel transport regimes in graphene
Novel transport regimes in graphene
Kong, Jian Feng
Transport phenomena in solids -- such as energy and charge flows in response to external fields -- is a subject of fundamental interest for solid state physics. Carrier transport exhibits a wide variety of intriguing and potentially useful behaviors arising due to a rich and complex interplay between electron-disorder, electron-electron, and electron-phonon interactions. Graphene, a newly discovered carbon one-atom-thick material, has unique transport characteristics, some of which are already well understood, whereas some are being under investigation or are waiting to be discovered. The two-dimensional character and exceptional cleanness of graphene, as well as gate tunability of the carrier density and electron-electron interactions, make graphene an excellent platform to study a range of new transport regimes, such as quantum-coherent ballistic transport, electron hydrodynamics and energy dissipation at the atomic scale. We will study ballistic transport in the context of electronic lensing. We will also demonstrate that electron-electron scattering alters ballistic transport in a dramatic way, giving rise to hole backflows and "memory effects", and leading to experimental signatures such as negative non-local resistance. Upon further increase of the electron-electron interaction strength, the system enters the hydrodynamic regime, where a host of new phenomena can emerge. We also show that the electron-disorder interactions have important implications for energy transport, with energy dissipation occurring predominantly at atomic-scale defects. In this thesis, we will provide a detailed discussion of these topics and their connection to the ongoing experiments.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 121-130).
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Intergalactic baryon enrichment and implications for galaxy evolution at high redshift
Intergalactic baryon enrichment and implications for galaxy evolution at high redshift
Cooper, Thomas (Thomas J.), Ph. D. Massachusetts Institute of Technology
In this thesis we present several surveys of heavy element absorber characteristics at high redshift, gauging properties of diffuse intra- and intergalactic gas in the first several Gyr of the Universe. At z ~ 3.5, we study chemical abundances of Lyman limit systems (LLSs) and evaluate their potential to represent expected reservoirs of cold, low-metallicity gas whose accretion onto galaxies is necessary to maintain star formation. In an initial survey focused only on LLSs identified as potential lowmetallicity absorbers, based on the absence of metal lines in low-resolution spectra, we indeed found the selected systems have low abundances, with a median of [M/H]~ -2.2 and several systems at [M/H]~ -3, comparable to the intergalactic medium. While this result is tempting to interpret as evidence that a sizable fraction of LLSs are candidates of low-metallicity gas accreting onto galaxies, in a follow-up study of all LLSs at z ~ 3.5 we found that LLS abundances can be reasonably described by a unimodal distribution with [M/H]~ -2.5. Additional diagnostics are hence needed to evaluate if (and how many) low abundance LLSs arise from accretion flows, since the overall LLS abundance distribution overlaps heavily with the IGM at this epoch. In a seperate work that constitutes the largest study of multiple ions in individual metalline absorption systems at z >/~ 6, we find that the bulk of high-redshift absorption systems are low-ionization and low-metallicity. Since H i absorption cannot be seen at z >/~ 6, we further argue from incidence rates and absorber characteristics that these absorbers are analogous to strong neutral hydrogen systems seen at lower redshift. We conclude that the non-detection of weaker H i absorption systems (such as LLSs) is consistent with lower metallicities and lower ionization states in the circumgalactic medium than is seen at later times.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 187-194).
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Cavity quantum electrodynamics with ensembles of ytterbium-171
Cavity quantum electrodynamics with ensembles of ytterbium-171
Braverman, Boris
In this thesis, I present the realization of a system applying the tools of cavity quantum electrodynamics to an atomic optical lattice clock. We design and implement a unique experimental cavity structure, with a small radius of curvature mirror on one side and a large mirror on the other side. With this structure, we are able to probe ytterbium-171 atoms in both the weak and strong coupling regimes of cavity quantum electrodynamics. This asymmetric micromirror structure simultaneously offers strong light-atom coupling, mechanical robustness, and excellent access to a large cavity volume. We develop a simple but accurate model for strong light-atom interactions in our system, which allows us to predict the performance of both cavity-assisted quantum non demolition measurements of the atomic state, and the back-action of the probing light onto the atomic state. We find theoretically, and confirm experimentally, that probing the atom-cavity system with two frequencies at the vacuum Rabi peaks of a system with strong collective light-atom coupling generates the largest possible entanglement between the probing light and the atomic state. With this scheme, we demonstrate atomic number measurements within a factor of 2 of the quantum Fisher information limit. By using the quantum back-action of the probing light on the atomic ensemble, we perform squeezing by cavity feedback. We produce states with -11±1 dB of variance squeezing and 14±1 dB of anti squeezing. Using theoretical simulations, we show that states with near-unitary squeezing offer significant advantages for improving atomic clocks compared to previous work. The ability to load large atomic ensembles in the strong coupling regime in our system offers several routes to the generation of highly entangled non-Gaussian quantum states. Such states can be produced by heralded measurements, or by global atom-atom interactions based on unitary spin squeezing. Altogether, we realize a system of unprecedented versatility and great potential for performing a large variety of hybrid atomic clock and cavity QED experiments.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; Cataloged from student-submitted PDF version of thesis.; Includes bibliographical references (pages 313-328).
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Introducing spin-orbit interaction in graphene
Introducing spin-orbit interaction in graphene
Khoo, Jun Yong
The excellent electron properties of graphene, an atomically-thin material with record-high carrier mobility and gate tunability, make it central to modern nanoscience. However, the spin-orbit interaction (SOI) naturally present in graphene is extremely weak and has yet to be observed experimentally. This presents an obstacle for accessing novel phenomena in transport and optics, in particular those related to topological properties. This thesis seeks to address this limitation by artificially introducing SOI in graphene sandwiched between other atomically-thin materials that can produce an interfacial SOI in graphene. In particular, it is demonstrated that a strong SOI, naturally present in the two-dimensional materials such as transition metal dichalcogenides (TMD), can be partially transferred to graphene via the proximity effect. We predict a range of novel phenomena arising in graphene bilayers with layer-asymmetric SOI induced by a proximal TMD layer. These include a gate-tunable SOI, a gate-tunable intrinsic valley-Hall conductivity, as well as a gate-tunable edge conductivity, to name just a few. These findings will facilitate exploring previously inaccessible spin-related phenomena in graphene and other van der Waals heterostructures.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 131-146).
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