Physics - Ph.D. / Sc.D.
http://hdl.handle.net/1721.1/7695
2016-07-01T04:38:11ZPrecision magnetometry and imaging via quantum manipulation of spins in diamond
http://hdl.handle.net/1721.1/103247
Precision magnetometry and imaging via quantum manipulation of spins in diamond
Arai, Keigo
.Precise control of quantum states is a cornerstone of quantum science and technology. Recently, a multi-level electronic spin system in a robust room-temperature solid, based on the nitrogen-vacancy (NV) color center in diamond, has emerged as a leading platform for quantum sensing as well as quantum information processing at room temperature. Developing new approaches to high-precision NV spin manipulation provides key insights for advancing these quantum technologies. In this thesis, I demonstrate three experimental methods for controlling NV spins with various concentrations toward high-performance magnetic field sensing and imaging. First, the wide-field optical magnetic microscopy experiment provides ensemble- NV control via continuous-wave electron spin resonance and camera-based parallel spin-state readout. This microscope offers a factor of 100 larger field-of-view compared to the confocal detection size, which enables magnetic imaging of populations of living bacteria. Second, the Fourier magnetic imaging experiment demonstrates for the first time multiple-NV control using phase encoding. Pulsed magnetic field gradients encode in the NV spin phase the information about the position of the NV centers as well as the external magnetic field in the Fourier-space. This scheme allows 100-fold improvement in spatial resolution beyond the optical diffraction limit, and has higher signal-to-noise ratio than other super-resolution imaging techniques when applied to NV spins. Third, the geometric phase magnetometry experiment employs single-NV control using a Berry sequence, consisting of off-resonant microwaves whose parameters vary along a cyclic path, thereby realizing 100 times larger magnetic field dynamic-range compared to the typical Ramsey-type interferometry approach. Finally, I discuss the possibilities of combining these techniques to realize various other quantum applications in future work.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 183-209).
2016-01-01T00:00:00ZFriction under microscope with trapped ions in optical lattices
http://hdl.handle.net/1721.1/103245
Friction under microscope with trapped ions in optical lattices
Bylinskii, Alexei
In recent years, cold-atom experiments have moved towards atomic systems with increasingly stronger interactions. One goal is to emulate condensed-matter phenomena in an ultimately controlled system by studying the motion of atoms in optical lattices. Trapped ions are the epitome of a strongly-interacting cold-atom system, but until now have been limited to simulating spin systems. In this thesis work, a toolbox is developed for combining trapped ions with optical lattices and for studying problems of atomic crystals in periodic potentials. One such problem of tremendous technological and economic importance is friction - a ubiquitous phenomenon that is poorly understood even at the atomic level (nanofriction), where stick-slip processes are known to be the dominant source of dissipation and wear. Friction is studied in this thesis work with unprecedented spatial resolution and control at the individual-atom level in the synthetic frictional interface between crystals of trapped ions (moving object) and an optical lattice (rigid corrugated substrate). These experiments address, at the atomic scale, four quintessential questions about friction: the dependence of friction on the load (corrugation depth), on material properties (object-substrate lattice mismatch), on the contact area (number of atoms at an atomically smooth contact) and on velocity and temperature. In particular, we observe the elusive regime of superlubricity - the vanishing of stick-slip friction - for ion crystals mismatched to the lattice. With increasing load, we observe superlubricity to break and stick-slip friction to reappear as a result of a long-theorized sliding-topinned structural transition known as the Aubry transition. Although these effects were initially predicted to occur in the infinite-atom limit, we find them to arise already at the level of two or three atoms in our system. The presented results could potentially lead to ways of engineering friction in nanomaterials or even at the macroscopic scale, and the system can further be used to study quantum many-body physics of solids in periodic potentials, potentially relevant to friction and surface physics at the nanoscale and at cold surfaces.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 197-207).
2016-01-01T00:00:00ZPrecision measurement of electron and positron flux in cosmic rays with the AMS-02 Detector
http://hdl.handle.net/1721.1/103243
Precision measurement of electron and positron flux in cosmic rays with the AMS-02 Detector
Chen, Hai, Ph. D. Massachusetts Institute of Technology
The cosmic ray electron and positron flux measurement can address a series of astrophysics and particle physics questions. This thesis presents an analysis of electron and positron flux from 0.5 GeV to 1 TeV using the first 30 months of data taking( over 41 billion events), with the AMS-02 detector on the International Space Station(ISS) 330-410 km above earth. A precise calibration of the Electromagnetic Calorimeter(ECAL) signals is performed to obtain stable energy measurement. A reconstruction algorithm for electromagnetic showers is implemented to measure energy and achieve high particle identification accuracy of electron and positron separating them from the proton background. The result of combined electron and positron flux measurement shows a smooth spectrum with no sharp structure. The spectral index ... above 30 GeV is observed to be ... (energy scale). This provides precise measurement for cosmic ray electrons and positrons and can contribute to probing the origin of cosmic rays, informing the studies of new physics..
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 159-169).
2016-01-01T00:00:00ZAn action principle for dissipative fluid dynamics
http://hdl.handle.net/1721.1/103242
An action principle for dissipative fluid dynamics
Crossley, Michael James
Fluid dynamics is the universal theory of low-energy excitations around equilibrium states, governing the physics of long-lived modes associated with conserved charges. Historically, fluid dynamics has been formulated at the level of equations of motion, in terms of a local fluid velocity and thermodynamic quantities. In this thesis, we describe a new formulation of fluid dynamics in terms of a path integral, which systematically encodes the effects of thermal and quantum fluctuations. In our formulation, the dynamical degrees of freedom are Stuckelberg-type fields associated to the conserved quantities, which are subject to natural symmetry considerations, and the time evolution of the path integral is along the closed-time contour. Our formulation recovers the standard hydrodynamics, including the expected constraints from thermodynamics and the fluctuation-dissipation theorem, as well as an additional non-linear generalization of the Onsager relations. We demonstrate an emergent supersymmetry in the "classical statistical" limit of our theory. For the non-linear fluid, the formalism is encoded in a non-trivial differential geometric structure, with a non vanishing torsion tensor required to recover the correct physics of the most general fluid. Finally, we discuss progress in obtaining a holographic derivation of the action formulation at the ideal level, in which the low energy degrees of freedom emerge naturally as the relative embedding of the boundary and horizon hypersurfaces.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 193-199).
2016-01-01T00:00:00Z