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Articles on this Page
- 12/31/13--16:00: _Cumulative effects ...
- 12/31/79--16:00: _Theoretical studies...
- 12/31/14--16:00: _Sterile neutrinos i...
- 12/31/82--16:00: _Localization and lo...
- 12/31/77--16:00: _Two photon transiti...
- 12/31/15--16:00: _An action principle...
- 12/31/15--16:00: _Precision measureme...
- 12/31/15--16:00: _Friction under micr...
- 12/31/15--16:00: _Precision magnetome...
- 07/21/16--06:56: _A queueing theoreti...
- 12/31/41--16:00: _Propagation of elec...
- 12/31/15--16:00: _Effects of resonanc...
- 12/31/15--16:00: _Semiclassical studi...
- 12/31/15--16:00: _Novel angular and f...
- 12/31/15--16:00: _21 cm cosmology wit...
- 12/31/15--16:00: _Lessons on interact...
- 12/31/64--16:00: _Brillouin scatterin...
- 12/31/54--16:00: _Measurement of the ...
- 12/31/38--16:00: _Apparatus for inves...
- 12/31/15--16:00: _A measurement of th...
- 12/31/14--16:00: Sterile neutrinos in cold climates
- 12/31/77--16:00: Two photon transitions in laser pumped submillimeter lasers
- 12/31/15--16:00: An action principle for dissipative fluid dynamics
- 12/31/15--16:00: Friction under microscope with trapped ions in optical lattices
- 12/31/41--16:00: Propagation of electromagnetic pulses in the ionosphere
- 12/31/15--16:00: Semiclassical studies of decoherence produced by scattering
- 12/31/15--16:00: 21 cm cosmology with optimized instrumentation and algorithms
- 12/31/15--16:00: Lessons on interacting quantum field theories from string theory
- 12/31/64--16:00: Brillouin scattering and coherent phonon generation.
Cumulative effects in quantum algorithms and quantum process tomography
Hess, Shelby Kimmel
This thesis comprises three results on quantum algorithms and quantum process tomography. In the first section, I create a tool that uses properties of the quantum general adversary bound to upper bound the query complexity of Boolean functions. Using this tool I prove the existence of O(1)-query quantum algorithms for a set of functions called FAULT TREES. To obtain these results, I combine previously known properties of the adversary bound in a new way, as well as extend an existing proof of a composition property of the adversary bound. The second result is a method for characterizing errors in a quantum computer. Many current tomography procedures give inaccurate estimates because they do not have adequate methods for handling noise associated with auxiliary operations. The procedure described here provides two ways of dealing with this noise: estimating the noise independently so its effect can be completely understood, and analyzing the worst case effect of this noise, which gives better bounds on standard estimates. The final section describes a quantum analogue of a classical local search algorithm for Classical k-SAT. I show that for a restricted version of Quantum 2-SAT, this quantum algorithm succeeds in polynomial time. While the quantum algorithm ultimately performs similarly to the classical algorithm, quantum effects, like the observer effect, make the analysis more challenging.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 129-134).
Theoretical studies for microwave remote sensing of layered random media
Zuniga, Michael Anthony
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.; Vita.; Includes bibliographical references.
Sterile neutrinos in cold climates
Jones, Benjamin J. P
Measurements of neutrino oscillations at short baselines contain an intriguing set of experimental anomalies that may be suggestive of new physics such as the existence of sterile neutrinos. This three-part thesis presents research directed towards understanding these anomalies and searching for sterile neutrino oscillations. Part I contains a theoretical discussion of neutrino coherence properties. The open-quantum-system picture of neutrino beams, which allows a rigorous prediction of coherence distances for accelerator neutrinos, is presented. Validity of the standard treatment of active and sterile neutrino oscillations at short baselines is verified and non-standard coherence loss effects at longer baselines are predicted. Part II concerns liquid argon detector development for the MicroBooNE experiment, which will search for short-baseline oscillations in the Booster Neutrino Beam at Fermilab. Topics include characterization and installation of the MicroBooNE optical system; test-stand measurements of liquid argon optical properties with dissolved impurities; optimization of wavelength-shifting coatings for liquid argon scintillation light detection; testing and deployment of high-voltage surge arrestors to protect TPC field cages; and software development for optical and TPC simulation and reconstruction. Part III presents a search for sterile neutrinos using the IceCube neutrino telescope, which has collected a large sample of atmospheric-neutrino-induced events in the 1-10 TeV energy range. Sterile neutrinos would modify the detected neutrino flux shape via MSW-resonant oscillations. Following a careful treatment of systematic uncertainties in the sample, no evidence for MSW-resonant oscillations is observed, and exclusion limits on 3+1 model parameter space are derived. Under the mixing assumptions made, the 90% confidence level exclusion limit extends to ... , and the LSND and MiniBooNE allowed regions are excluded at >99% confidence level.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 313-339).
Localization and low temperature transport in disordered one-dimensional systems
Stone, Alfred Douglas
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1983.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE; Includes bibliographical references.
Two photon transitions in laser pumped submillimeter lasers
Drozdowicz, Zbigniew Marian
Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Physics.; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.; Vita.; Includes bibliographical references.
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).
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).
Friction under microscope with trapped ions in optical lattices
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).
Precision magnetometry and imaging via quantum manipulation of spins in diamond
.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).
A queueing theoretic analysis of contractors' sequential bidding problems.
Zacks, Leonard Harvey
Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1970. Ph.D.; Vita.; Bibliography: leaves 114-115.
Propagation of electromagnetic pulses in the ionosphere
Austin, Pauline M. (Pauline Morrow)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1942.; Vita.; Includes bibliographical references (leaf 57).
Effects of resonances and spin-curvature coupling in extreme mass ratio inspirals
Since Einstein proposed the theory of general relativity (GR) as a theory of gravity, it has passed all experimental checks and tests. Until recently, all of these tests have been done in the weak gravity limit. The first test of strong-field GR came just a few months ago, when the LIGO collaboration directly detected gravitational waves for the first time. Using gravitational waves as a tool to test the validity of GR requires us to know the waveforms that GR predicts from various sources. The ultimate goal of the research described in this thesis is to compute the waveform generated by a stellar mass Kerr black hole as it inspirals into a much more massive black hole (SMBH). To compute this waveform, we must first compute the inspiral trajectory of the stellar mass black hole. The trajectory of the smaller black hole differs from the geodesic structure taught in GR textbooks due to the influence of this body's mass and spin. In this thesis, I examine these two effects separately. Later work will need to consider the two effects simultaneously, but the separate impact of these effects provides insight which helps us to understand how to model these sources. The small body's mass perturbs the spacetime and pushes its trajectory away from textbook geodesic motion. I show how to compute the dissipative part of this "self force," whose average impact is equivalent to the loss of energy and angular momentum due to gravitational wave emission. I study in particular how the self force's averaged behavior changes near orbital resonances, quantifying the impact that such resonances will have on the small body's inspiral. The small body's spin couples to spacetime curvature. This coupling leads to a force which also pushes the small body's trajectory away from the geodesic. This force is comparable in magnitude to the self force associated with the small body's mass, indicating that future work will need to assess the impact of these effects together in a self consistent way in order to make accurate inspiral waveforms.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references.
Semiclassical studies of decoherence produced by scattering
Schram, Matthew Christopher
The conventional notion of coherent atom-surface scattering originates from the existence of Bragg peaks in elastic scattering. The helium atom acts as a quantum mechanical matter wave that is coherent with itself; the well-defined phase relationship of the particle beam at the different spatial positions at surface impact implies the possibility of different non-specular outgoing beams thanks to the constructive interference of the emitted waves from each surface atom. Moreover, we still observe diffraction peaks when scattering off a lattice at finite temperature, although the peaks are here diminished by the Debye-Waller factor. However, in the case of inelastic scattering, the surface particles are displaced by the scattering atom itself and may then emit or absorb one or more phonons to the scatterer. Acoustic phonons produced by this process are gapless excitations; hence, extremely long-wavelength phonons will contribute vanishingly small shifts in energy and momentum. The difficulty in observing this is exacerbated due to the roughly 1eV resolution of high energy helium scattering experiments. So through phonon excitation the surface has "measured" the particle's presence which acts to destroy quantum coherence, though we still observe diffraction spots which imply coherent scattering. How do we reconcile these disparate viewpoints? We propose a new way of looking at the question of coherence in atom-surface scattering. Instead of considering a single beam of helium particles, we instead use semiclassical techniques to simulate an initially coherent superposition of helium particles with equal probabilities of interacting with the surface or not interacting with the surface. We then evolve the classical mechanical trajectories, and recombine the atoms after scattering to observe the resulting interference pattern. The degree to which phonons are excited in the lattice by the scattering process dictates the fringe contrast of the interference pattern of the resulting beams. We show that for a wide range of conditions, despite the massive change in the momentum perpendicular to the surface, we can still expect to have coherent (in the superposition sense) scattering.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 146-152).
Novel angular and frequency manipulation of light in nano-scaled dielectric photonic systems
Shen, Yichen, Ph. D. Massachusetts Institute of Technology
Humankind has long endeavored to control light. In modern society, with the rapid development of nanotechnology, the control of light is moving toward devices at micrometer and even nanometer scales. At such scales, traditional devices based on geometrical optics reach their fundamental diffraction limits and cease to work. Nano-photonics, on the other hand, has attracted wide attention from researchers, especially in the last decade, due to its ability to manipulate light at the nanoscale. In this thesis, we explore novel control of light created by nanophotonic structures, with a common theme on light interference in nanoscaled dielectric photonic systems. The first part of the thesis focuses on broadband angular selective nanophotonic systems. We survey the literatures and the current state of the art focused on enabling optical broadband angular selectivity. We also present a novel way of achieving broadband angular selectivity using Brewster mode in nanophotonic systems. We propose two categories of potential applications for broadband angularly selective systems. The first category aims at enhancing the efficiency of solar energy harvesting, through photovoltaic process or solar thermal process. The second category aims at enhancing light extracting efficiency and detection sensitivity. Finally, we discuss the most prominent challenges in broadband angular selectivity and some prospects on how to solve these challenges. The second part of the thesis focuses on spectrum control of light using all-dielectric surface resonator. We proposes a new structural color generation mechanism that produces colors by the Fano resonance effect on thin photonic crystal slab. We experimentally realize the proposed idea by fabricating the samples that show resonance-induced colors with weak dependence on the viewing angle. We also show that the colors can be dynamically tuned by stretching the photonic crystal slab fabricated on an elastic substrate. In a follow up work, we address how to overcome the challenge of mode leaking on dielectric substrate. We present a class of low-index zigzag surface structure that supports resonance modes even without index contrast with the substrate. In the third part, we investigate neuromorphic computation using the interference of light in on-chip dielectric photonic waveguide network. We first mathematically prove that conventional neural networks architecture can be equivalently represented by nanoscaled optical systems. We then experimentally demonstrate that our optical neural networks are able to give equivalent accuracy on a standard training datasets. In the last part, we show that in principle optical neural nets are at least 3 orders of magnitude faster and power efficient in forward propagation than conventional neural nets.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 93-114).
21 cm cosmology with optimized instrumentation and algorithms
Zheng, Haoxuan, Ph. D. Massachusetts Institute of Technology
Precision cosmology has made tremendous progress in the past two decades thanks to a large amount of high quality data from the Cosmic Microwave Background (CMB), galaxy surveys and other cosmological probes. However, most of our universe's volume, corresponding to the period between the CMB and when the first stars formed, remains unexplored. Since there were no luminous objects during that period, it is called the cosmic "dark ages". 21 cm cosmology is the study of the high redshift universe using the hyperfine transition of neutral hydrogen, and it has the potential to probe that unchartered volume of our universe and the ensuing cosmic dawn, placing unprecedented constraints on our cosmic history as well as on fundamental physics. My Ph.D. thesis work tackles the most pressing observational challenges we face in the field of 21 cm cosmology: precision calibration and foreground characterization. I lead the design, deployment and data analysis of the MIT Epoch of Reionization (MITEoR) radio telescope, an interferometric array of 64-dual polarization antennas whose goal was to test technology and algorithms for incorporation into the Hydrogen Epoch of Reionization Array (HERA). In four papers, I develop, test and improve many algorithms in low frequency radio interferometry that are optimized for 21 cm cosmology. These include a set of calibration algorithms forming redundant calibration pipeline which I created and demonstrated to be the most precise and robust calibration method currently available. By applying this redundant calibration to high quality data collected by the Precision Array for Probing the Epoch of Reionization (PAPER), we have produced the tightest upper bound of the redshifted 21 cm signals to date. I have also created new imaging algorithms specifically tailored to the latest generation of radio interferometers, allowing them to make Galactic foreground maps that are not accessible through traditional radio interferometry. Lastly, I have improved on the algorithm that synthesizes foreground maps into the Global Sky Model (GSM), and used it to create an improved model of diffuse sky emission from 10 MHz through 5 THz.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 213-236).
Lessons on interacting quantum field theories from string theory
Wang, Yifan, Ph. D. Massachusetts Institute of Technology
In this thesis, we use string theory constructions and dualities to explore various features of interacting quantum field theories. We begin with an overview in Chapter 1, of past and recent developments in quantum field theories, explaining the advantages of string theoretic techniques over traditional approaches in answering a range of questions about interacting dynamics. In Chapter 2 we study the holographic duality between the 6d (1, 1) Ak-1 little string theory (LST) and type II string theory in the double scaled limit. By identifying the low energy states, which are Cartan gluons in the 6d maximal super-Yang-Mills (SYM) that describes the massless sector of the LST, we compute the four-point amplitudes from both sides of the duality and demonstrate matching results. Since the two computations concern different regimes in the parameter space, their amazing agreement implies the presence of certain nonrenormalization theorems in the 6d SYM. In Chapter 3, motivated by the AdS/CFT duality, we develop a systematic procedure to derive an off-shell action for hydrodynamics from classical Einstein gravity. We first identity the boundary fluid degrees of freedom in the hydrodynamic regime, in terms of gapless modes of the metric in the bulk gravity. This allows us to derive an off-shell action, for relativistic fluids that have gravity duals, at leading order in derivative expansion, by explicitly integrating out gapped degrees of freedom in the bulk. We also explain the strategy to incorporate dissipation and higher order effects. In Chapter 4, we discuss 4d N = 2 superconformal field theories (SCFT) of the Argyres-Douglas (AD) type, which can be constructed in string/M theory by either wrapping M5 branes on punctured Riemann surface or probing 3-fold singularity by IIB string. We classify the punctures (irregular defects in Hitchin system) on the Riemann surface in the former construction, that will give rise to N = 2 SCFTs and demonstrate how to extract exact information about the Coulomb branch spectrum and central charges. We further identify these AD theories constructed from M5 branes with a special class of theories from IIB probing compound Du Val (cDV) singularities, thereby establishing a mathematical connection between singular Hitchin systems and cDV singularities through N = 2 SCFTs. We end with a short summary and outlook for future directions in Chapter 5.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 185-194).
Brillouin scattering and coherent phonon generation.
Chiao, Raymond Yu
Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1965. Ph.D.
Measurement of the thermodynamic properties of a paramagnetic salt below one degree kelvin by a non-calorimetric method
Jennings, Laurence Duane, 1929-
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1955.; Includes bibliographical references (leaves 66-67).
Apparatus for investigating the effects of cathode rays on biological material in vacuum
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1939.; Vita.; Includes bibliographical references (leaf 101).
A measurement of the two-photon exchange effect in elastic electron-proton scattering with OLYMPUS
Russell, Rebecca Lynn
Elastic electron-proton scattering has long been the tool of choice for the study of the proton form factors, GE(Q 2 ) and GM(Q2 ), which describe the electric and magnetic distributions of the proton as a function of momentum transfer. Recent experiments, measuring the form factors from polarization observables in polarized elastic electron-proton scattering, have found values of the ratio GE(Q2 )/GM(Q2) at high Q2 that contradict the results from unpolarized measurements. A proposed explanation for this discrepancy is the unaccounted two-photon exchange radiative correction, which could affect the unpolarized measurements. As this effect is currently not possible to calculate in a model-independent way, the OLYMPUS experiment was designed to make a direct measurement of it by measuring the elastic positron-proton to electron-proton scattering cross section ratio. The experiment was run in 2012 at DESY using the BLAST spectrometer and the DORIS positron and electron beams at 2 GeV incident on a gaseous hydrogen target. To analyze the data, a careful reconstruction of the scattering events, detailed simulation of the experimental setup, and full radiative corrections to the measured cross sections were performed. Preliminary results for the experiment show a statistically significant two-photon exchange effect, increasing over the measurement range of 0.6 GeV2