Physics - Bachelor's degree
http://hdl.handle.net/1721.1/7696
2015-01-31T13:11:50ZQuantum capacitance measurements of single-layer molybdenum disulfide
http://hdl.handle.net/1721.1/92704
Quantum capacitance measurements of single-layer molybdenum disulfide
Kononov, Alina
Through this thesis, heterostructures composed of a thin layer of hexagonal boron nitride atop a monolayer of molybdenum disulfide were fabricated with the goal of measuring quantum capacitance and probing the transition metal dichalcogenide's density of states. In the final devices, no modulation of the quantum-capacitance was observed due to large Schottky barriers between the metal contacts and the molybdenum disulfide. Lessons learned from this investigation inform improved fabrication and measurement techniques for future iterations of these fascinating devices.
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 45-46).
2014-01-01T00:00:00ZQuantum state reconstruction and tomography using phase-sensitive light detection
http://hdl.handle.net/1721.1/92703
Quantum state reconstruction and tomography using phase-sensitive light detection
Mello, Olivia L
In this thesis we present an optical and electronic setup that is capable of performing coherent state tomography. We fully characterize it in order to verify whether or not it will be capable to perform non-demolition homodyne detection of squeezed light in a high-finesse cavity QED setup with an ensemble of Cesium atoms coupled to the cavity. After quantifying sources of noise, the photodiode efficiency, we perform a series of measurements of low photon number coherent states and compare them against the standard quantum limit. We discuss a variety of technical challenges encountered in such systems and some methods to overcome them. Lastly, we test the apparatus' ability to do quantum state tomography and quantum state reconstruction by reconstructing the density matrix and Wigner functions for low photon-number coherent states.
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 69-70).
2014-01-01T00:00:00ZThe life of quanta : entanglement wormholes and the second law
http://hdl.handle.net/1721.1/92702
The life of quanta : entanglement wormholes and the second law
Gharibyan, Hrant
This thesis explores two different topics in physics. The first is related to the study of the ER = EPR conjecture that relates the entanglement entropy of a collection of black holes to the cross sectional area of Einstein-Rosen (ER) bridges (or wormholes) connecting them. We show that the geometrical entropy of classical ER bridges satisfies the subadditivity, triangle, strong subadditivity, and CLW inequalities. These are nontrivial properties of entanglement entropy, so this is evidence for ER = EPR. We further show that the entanglement entropy associated to classical ER bridges has nonpositive tripartite information. This is not a property of entanglement entropy, in general. For example, the entangled four qubit pure state IGHZ4) = (I0000) + (I1111))/[square root]2 has positive tripartite information, so this state cannot be described by a classical ER bridge. Large black holes with massive amounts of entanglement between them can fail to have a classical ER bridge if they are built out of IGHZ4) states. States with nonpositive tripartite information are called monogamous. We conclude that classical ER bridges require monogamous EPR correlations. The second is a generalization of the second law of thermodynamics. We prove a generalization of the classic Groenewold-Lindblad entropy inequality, combining decoherence and the quantum Bayes theorem into a simple unified picture where decoherence increases entropy while observation decreases it. This provides a rigorous quantum-mechanical version of the second law of thermodynamics, governing how the entropy of a system evolves under general decoherence and observation. The powerful tool of spectral majorization enables both simple alternative proofs of the classic Lindblad and Holevo inequalities without using strong subadditivity, and also novel inequalities for decoherence and observation that hold not only for von Neumann entropy, but also for arbitrary concave entropies.
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 105-111).
2014-01-01T00:00:00ZHigher levels of the transmon qubit
http://hdl.handle.net/1721.1/92701
Higher levels of the transmon qubit
Bader, Samuel James
This thesis discusses recent experimental work in measuring the properties of higher levels in transmon qubit systems. The first part includes a thorough overview of transmon devices, explaining the principles of the device design, the transmon Hamiltonian, and general Circuit Quantum Electrodynamics concepts and methodology. The second part discusses the experimental setup and methods employed in measuring the higher levels of these systems, and the details of the simulation used to explain and predict the properties of these levels.
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 91-95).
2014-01-01T00:00:00Z