Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1961. / Includes bibliographical references (leaf [106]). / by David S. Wiley. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1951. / Vita. / Includes bibliographical references (leaves 266-274). / by Robert Auger Dudley. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 45-46). / This work considers some implications of viewing gravity as an emergent force. In such a viewpoint, general relativity arises as the thermodynamic limit of some microscopic theory. As such, one would expect the macroscopic variables such as the curvature tensors to fluctuate about their mean. This thesis presents a method for analyzing the effects of curvature fluctuations on spacetime thermodynamics. This is done by examining the evolution equations for time-like and null congruences, and recasting them as stochastic differential equations. The purpose of viewing the congruence evolution equations as stochastic is in the spirit of nonequilibrium thermodynamics, and may lead to an application of the fluctuation-dissipation theorem to spacetime. It is expected that this reformulation of the congruence equations will lead to further insights on the effects of fluctuations in general relativity. / by Antony John Speranza. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004. / Includes bibliographical references (leaf 43). / The Laser Interferometer Gravitational-wave Observatory (LIGO) measures relative displacements of the interferometer mirrors induced by passing gravitational waves (GWs). At low frequencies, typically below 30 Hz, seismic noise is the dominant noise source that limits the sensitivity with which GW-induced mirror displacements can be measured. To shield the mirrors from the seismically driven motion of the ground, they are suspended from pendula which are in turn mounted on optical platforms with vibration isolation systems. The Advanced LIGO goal for strain sensitivity is factor of 10 to 15 lower than that for Initial LIGO. This requires improved seismic isolation techniques to reduce the seismic noise limit by this factor. This is being achieved in two ways: active vibration isolation of the optical platform on which the suspended mirrors are mounted; and suspension of the interferometer mirrors from the final stage of multiple pendula. In this thesis we characterize the dynamics of a prototype quadruple pendulum system. The figure of merit in evaluating and improving the performance of the quadruple pendulum is the motion of the mirror at frequencies between 1 and 100 Hz. To determine this, it is necessary to measure the frequency response (transfer functions) of the mirror displacement to motion of the penultimate mass of the pendulum. We describe the construction of a sensing and actuation system used to measure the transfer functions between the third and fourth masses, toward the ultimate goal of exploring the possibilities of third-mass system control. The measured transfer functions were compared to theoretical predictions generated by a simplified computer simulation of the complex system. / by Andrew C. Thomas. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 66-73). / In conventional superconductors the superconducting gap in the electronic excitation spectrum prevents scattering of low energy electrons. In high temperature superconductors (HTS) an additional gap, the pseudogap, develops well above the superconducting transition temperature Tc. The identity of this pseudogap and its relationship to high temperature superconductivity is one of the most interesting outstanding problems in condensed matter physics today. In this thesis I present a new avenue of investigating the pseudogap state, using scanning tunneling microscopy (STM) of resonances generated by single atom scatterers. First, I report that impurity resonance peaks, near zero bias in the excitation spectrum, continue to exist above the superconducting transition temperature and prove that the impurity resonance peak is unchanged through the superconducting transition. I also show that native impurity resonances coexist spatially with the superconducting gap at low temperatures. These findings demonstrate that properties of impurity resonances in HTS are not determined by the nature of the superconducting state, as previously suggested, but instead provide new insights into the pseudogap state. I will further provide preliminary results of doping dependence as a probe to study the pseudogap. In addition to these scientific results, I will also discuss advances I have made in STM instrumentation, from a novel technology to provide the excitation for the coarse approach mechanism of the STM to current amplifier circuits for faster spectroscopy measurements. / by Kamalesh Chatterjee. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 217-221). / Understanding the underlying mechanisms involved in the interactions between nucleons is one of the fundamental problems in nuclear physics. Over roughly the last 70 years, this question has been approached on many different fronts. We believe that the theory underlying the interaction between nucleons is that between quarks and gluons described by Quantum Chromodynamics; however, a complete solution to the nucleon-nucleon interaction within this framework has yet to emerge. In parallel, the advent of polarization experiments involving both polarized beams and targets has provided new experimental avenues to test our understanding the reaction mechanisms involved in the nucleon-nucleon interaction. One important example is the electrodisintegration of the deuteron, ... (e[over-arrow], e'p)n, in particular the measurement of the beam-vector asymmetry, AV, and the tensor asymmetry, AT. Both of these asymmetries are sensitive to the d-wave components of the deuteron and are thus measurements of the effects of the tensor force in the nucleon-nucleon interaction. This work reports on measurements of AV and A T in the electrodisintegration of the deuteron that were performed by the BLAST collaboration at the Bates Linear Accelerator Center involving two data runs during 2004 and 2005. The measurements consisted of cross sections and asymmetries vs. missing momentum for a Q2 range of 0.1(GeV/c) 2 < Q2 < 0.5(GeV/c) 2 . Comparisons between Monte Carlo simulations based on a particular theoretical framework are made, and conclusions are drawn. / by Adam DeGrush. / Ph.D.

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.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1999. / Includes bibliographical references (p. 187-191). / by Nilanga Kumara Bamunusinha Liyanage. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 183-209). / .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. / by Keigo Arai. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1992. / Includes bibliographical references (leaves 100-102). / by Peter Kurt Fritschel. / Ph.D.