Investigating The Talbot Effect In Arrays Of Optical Dipole Traps For Neutral Atom Quantum Computing, 2019 California Polytechnic State University, San Luis Obispo

#### Investigating The Talbot Effect In Arrays Of Optical Dipole Traps For Neutral Atom Quantum Computing, Sergio Aguayo

*Physics*

Quantum computers are devices that are able to perform calculations not achievable for classical computers. Although there are many methods for creating a quantum computer, using neutral atoms offers the advantage of being stable when compared to other methods. The purpose of this investigation is to explore possible optical dipole trap configurations that would be useful for implementing a quantum computer with neutral atoms. Specifically, we computationally investigate arrays of pinholes, the diffraction pattern generated by them, and the onset of the Talbot effect in these traps. We manipulate the radius of the pinholes, the number of pinholes in the ...

Optimization Of Quantum Optical Metrology Systems, 2019 Louisiana State University

#### Optimization Of Quantum Optical Metrology Systems, Nicholas Michael Studer

*LSU Doctoral Dissertations*

It can be said that all of humanity's efforts can be understood as a problem of optimization. We each have a natural sense of what is ``good'' or ``bad'' and thus our actions tend towards maximizing -- or optimizing -- some notion of good and minimizing those things we perceive as bad or undesirable.

Within the sciences, the greatest form of good is knowledge. It is this pursuit of knowledge that leads to not only life-saving innovations and technology, but also to furthering our understanding of our natural world and driving our philosophical pursuits.

The principle method of obtaining knowledge in ...

Precision Of Parameter Estimation In Quantum Metrology, 2019 Louisiana State University and Agricultural and Mechanical College

#### Precision Of Parameter Estimation In Quantum Metrology, Chenglong You

*LSU Doctoral Dissertations*

The fundamental precision limit of an interferometer is crucial since it bounds the best possible sensitivity one could achieve using such a device. This thesis will focus on several different interferometers and try to give the ultimate precision bounds by carefully counting all the resources used in the interferometers.

The thesis begins with the basics of the quantum state of light. The fundamentals of quantum metrology are also reviewed and discussed. More specifically, the terminology of classical and quantum Cram\'er-Rao bound and classical and quantum Fisher information are introduced.

Chapter 3 discusses the conclusive precision bounds in two-mode interferometer ...

Optimization Of An Injection Locked Laser System For Cold Neutral Atom Traps, 2019 California Polytechnic State University, San Luis Obispo

#### Optimization Of An Injection Locked Laser System For Cold Neutral Atom Traps, Elliot M. Lehman

*Physics*

Many types of quantum systems are being explored for use in quantum computers. One type of quantum system that shows promise for quantum computing is trapped neutral atoms. They have long coherence times, since they have multiple stable ground states and have minimal coupling with other atoms and their environment, and they can be trapped in arrays, making them individu- ally addressable. Once trapped, they can be initialized and operated on using laser pulses. This experiment utilizes a pinhole diffraction pattern, which can trap atoms in both bright and dark areas. To maximize trap strength, an injection-locked laser amplification system ...

Kondo Signatures Of A Quantum Magnetic Impurity In Topological Superconductors, 2019 Shanghai Jiao Tong University

#### Kondo Signatures Of A Quantum Magnetic Impurity In Topological Superconductors, Rui Wang, Wei-Yi Su, Jian-Xin Zhu, Chin-Sen Ting, Hai Li, Changfeng Chen, Baigeng Wang, Xiaoqun Wang

*Physics & Astronomy Faculty Publications*

We study the Kondo physics of a quantum magnetic impurity in two-dimensional topological superconductors (TSCs), either intrinsic or induced on the surface of a bulk topological insulator, using a numerical renormalization group technique. We show that, despite sharing the p+ip pairing symmetry, intrinsic and extrinsic TSCs host different physical processes that produce distinct Kondo signatures. Extrinsic TSCs harbor an unusual screening mechanism involving both electron and orbital degrees of freedom that produces rich and prominent Kondo phenomena, especially an intriguing pseudospin Kondo singlet state in the superconducting gap and a spatially anisotropic spin correlation. In sharp contrast, intrinsic TSCs ...

Ultrafast Manipulation Of Topologically Enhanced Surface Transport Driven By Mid-Infrared And Terahertz Pulses In Bi2se3, 2019 Iowa State University and Ames Laboratory

#### Ultrafast Manipulation Of Topologically Enhanced Surface Transport Driven By Mid-Infrared And Terahertz Pulses In Bi2se3, Liang Luo, Xu Yang, X. Liu, Zhiyan Liu, Chirag Vaswani, Di Cheng, M. Mootz, Xin Zhao, Yongxin Yao, Cai-Zhuang Wang, Kai-Ming Ho, I. E. Perakis, M. Dobrowolska, J. K. Furdyna, Jigang Wang

*Ames Laboratory Accepted Manuscripts*

Topology-protected surface transport of ultimate thinness in three-dimensional topological insulators (TIs) is breaking new ground in quantum science and technology. Yet a challenge remains on how to disentangle and selectively control surface helical spin transport from the bulk contribution. Here we use the mid-infrared and terahertz (THz) photoexcitation of exclusive intraband transitions to enable ultrafast manipulation of surface THz conductivity in Bi2Se3. The unique, transient electronic state is characterized by frequency-dependent carrier relaxations that directly distinguish the faster surface channel than the bulk with no complication from interband excitations or need for reduced bulk doping. We determine the topological enhancement ...

Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, 2019 Chapman University

#### Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, José Raúl González Alonso, Nicole Yunger Halpern, Justin Dressel

*Mathematics, Physics, and Computer Science Faculty Articles and Research*

Out-of-time-ordered correlators (OTOCs) have received considerable recent attention as qualitative witnesses of information scrambling in many-body quantum systems. Theoretical discussions of OTOCs typically focus on closed systems, raising the question of their suitability as scrambling witnesses in realistic open systems. We demonstrate empirically that the nonclassical negativity of the quasiprobability distribution (QPD) behind the OTOC is a more sensitive witness for scrambling than the OTOC itself. Nonclassical features of the QPD evolve with timescales that are robust with respect to decoherence and are immune to false positives caused by decoherence. To reach this conclusion, we numerically simulate spinchain dynamics and ...

Control Of Light-Matter Interactions Via Nanostructured Photonic Materials, 2019 The Graduate Center, City University of New York

#### Control Of Light-Matter Interactions Via Nanostructured Photonic Materials, Nicholas Proscia

*All Dissertations, Theses, and Capstone Projects*

The thesis here investigates the manipulation of light-matter interactions via nanoscale engineering of material systems. When material systems are structured on the nanoscale, their optical responses can be dramatically altered. In this thesis, this is done in two primary ways: One method is by changing the geometry of nanostructures to induce a resonant behavior with incident electromagnetic field of optical wavelengths. This allows field enhancement in highly localized areas to strengthen exotic light-matter interactions that would otherwise be too weak to measure or for practical use. In this regard, the work presented here studies a voltage produced in a metal ...

Peculiar Optical Properties Of Bilayer Silicene Under The Influence Of External Electric And Magnetic Fields, 2019 Academia Sinica

#### Peculiar Optical Properties Of Bilayer Silicene Under The Influence Of External Electric And Magnetic Fields, Thi-Nga Do, Godfrey Gumbs, Po-Hsin Shih, Danhong Huang, Chih-Wei Chiu, Chia-Yun Chen, Ming-Fa Lin

*Publications and Research*

We conduct a comprehensive investigation of the effect of an applied electric field on the optical and magneto-optical absorption spectra for AB-bt (bottom-top) bilayer silicene. The generalized tightbinding model in conjunction with the Kubo formula is efficiently employed in the numerical calculations. The electronic and optical properties are greatly diversified by the buckled lattice structure, stacking configuration, intralayer and interlayer hopping interactions, spin-orbital couplings, as well as the electric and magnetic fields (Ez ˆz & Bz ˆz ). An electric field induces spin-split electronic states, a semiconductor-metal phase transitions and the Dirac cone formations in different valleys, leading to the special absorption ...

Comparisons Of Performance Between Quantum And Classical Machine Learning, 2019 Southern Methodist University

#### Comparisons Of Performance Between Quantum And Classical Machine Learning, Christopher Havenstein, Damarcus Thomas, Swami Chandrasekaran

*SMU Data Science Review*

In this paper, we present a performance comparison of machine learning algorithms executed on traditional and quantum computers. Quantum computing has potential of achieving incredible results for certain types of problems, and we explore if it can be applied to machine learning. First, we identified quantum machine learning algorithms with reproducible code and had classical machine learning counterparts. Then, we found relevant data sets with which we tested the comparable quantum and classical machine learning algorithm's performance. We evaluated performance with algorithm execution time and accuracy. We found that quantum variational support vector machines in some cases had higher ...

Quadratic To Linear Magnetoresistance Tuning In Tmb4, 2019 Nanyang Technological University

#### Quadratic To Linear Magnetoresistance Tuning In Tmb4, Sreemanta Mitra, Jeremy Goh Swee Kang, John Shin, Jin Quan Ng, Sai Swaroop Sunku, Tai Kong, Paul C. Canfield, B. Sriram Shastry, Pinaki Sengupta, Christos Panagopoulos

*Ames Laboratory Accepted Manuscripts*

The change of a material's electrical resistance (*R*) in response to an external magnetic field (*B*) provides subtle information for the characterization of its electronic properties and has found applications in sensor and storage related technologies. In good metals, Boltzmann's theory predicts a quadratic growth in magnetoresistance (MR) at low *B* and saturation at high fields. On the other hand, a number of nonmagnetic materials with weak electronic correlation and low carrier concentration for metallicity, such as inhomogeneous conductors, semimetals, narrow gap semiconductors and topological insulators, and two dimensional electron gas, show positive, nonsaturating linear magnetoresistance (LMR). However ...

The Road Less Traveled: Resonant Bose-Einstein Condensates Via A Hyperspherical Lowest-Order Constrained Variational Approach, 2019 University of Colorado at Boulder

#### The Road Less Traveled: Resonant Bose-Einstein Condensates Via A Hyperspherical Lowest-Order Constrained Variational Approach, Michelle Wynne Ching Sze

*Physics Graduate Theses & Dissertations*

In this work, we study the ground state properties of a system of $N$ harmonically trapped bosons of mass $m$ interacting with two-body contact interactions, from small to large scattering lengths. This is accomplished in a hyperspherical coordinate system that is flexible enough to describe both the overall scale of the gas and two-body correlations. By adapting the lowest-order constrained variational (LOCV) method, we are able to semi-quantitatively attain Bose-Einstein condensate ground state energies even for gases with infinite scattering length. In the large particle number limit, our method provides analytical estimates for the energy per particle $E_0/N \approx ...

An Introduction To Supersymmetric Quantum Mechanics, 2019 Virginia Commonwealth University

#### An Introduction To Supersymmetric Quantum Mechanics, Vincent R. Siggia

*Theses and Dissertations*

In this thesis, the general framework of supersymmetric quantum mechanics and the path integral approach will be presented (as well as the worked out example of the supersymmetric harmonic oscillator). Then the theory will be specialized to the case of supersymmetric quantum mechanics on Riemannian manifolds, which will start from a supersymmetric Lagrangian for the general case and the special case for S2. Afterwards, there will be a discussion on the superfield formalism. Concluding this thesis will be the Hamiltonian formalism followed by the inclusion of deforma- tions by potentials.

Theoretical Studies Of The Structure And Stability Of Metal Chalcogenide Crntem (1≤N≤6, 1≤M≤8) Clusters, 2019 Virginia Commonwealth University

#### Theoretical Studies Of The Structure And Stability Of Metal Chalcogenide Crntem (1≤N≤6, 1≤M≤8) Clusters, Fnu Sweta Prabha

*Theses and Dissertations*

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, Cr_{n}Te_{m} clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr_{6}Te_{8} which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher ...

Non-Reciprocity In An Active Two-Dimensional Lattice Circuit, 2019 University of Colorado, Boulder

#### Non-Reciprocity In An Active Two-Dimensional Lattice Circuit, Justin White

*Undergraduate Honors Theses*

Circulators are crucial components in quantum computers that ensure that quantum information is coherently transported. Current commercial circula- tors are too bulky because they use permanent magnets, so producing chip- scale circulators is necessary to feasibly scale up the size of quantum computers using superconducting qubits. Using a model inspired by a paper by Rudner [2], I have designed a lattice circuit that will produce non-reciprocity, which is the property required for proper circulation. These lattice circuits are able to produce circulation because they have periodically time-dependent bonds that control interactions between the sites in the lattice. In this thesis ...

Three-Particle Systems With Resonant Subprocesses In A Finite Volume, 2019 Old Dominion University

#### Three-Particle Systems With Resonant Subprocesses In A Finite Volume, Raúl A. Briceño, Maxwell T. Hansen, Stephen R. Sharpe

*Physics Faculty Publications*

In previous work, we have developed a relativistic, model-independent three-particle quantization condition, but only under the assumption that no poles are present in the two-particle K matrices that appear as scattering subprocesses [M. T. Hansen and S. R. Sharpe, Phys. Rev. D 90, 116003 (2014); M. T. Hansen and S. R. Sharpe, Phys. Rev. D 92, 114509 (2015); R. A. Briceño et al., Phys. Rev. D 95, 074510 (2017).]. Here we lift this restriction, by deriving the quantization condition for identical scalar particles with a G-parity symmetry, in the case that the two-particle K matrix has a pole in the ...

Polarized Hyperon Production In Single-Inclusive Electron Positron Annihilation At Next-To-Leading Order, 2019 Old Dominion University

#### Polarized Hyperon Production In Single-Inclusive Electron Positron Annihilation At Next-To-Leading Order, Leonard Gamberg, Zhong-Bo Kang, Daniel Pitonyak, Marc Schlegel, Shinsuke Yoshida

*Physics Faculty Publications*

We study the production of polarized A-hyperons in electron-positron annihilation. We are particularly interested in the transverse-spin dependence of the cross section for unpolarized incident electron-positron pairs. At high energies this process may be described in the collinear twist-3 framework, where the hadronization transition of partons into a transversely polarized -hyperon can be written in terms of collinear twist-3 fragmentation matrix elements. We calculate the hard partonic cross sections and interference terms in perturbative QCD to next-to-leading order accuracy. We find that the QCD equation of motion plays a crucial role in our analysis. As a byproduct, assuming the validity ...

Deformations Of G2-Structures, String Dualities And Flat Higgs Bundles, 2019 University of Pennsylvania

#### Deformations Of G2-Structures, String Dualities And Flat Higgs Bundles, Rodrigo De Menezes Barbosa

*Publicly Accessible Penn Dissertations*

We study M-theory compactifications on G2-orbifolds and their resolutions given by total spaces of coassociative ALE-fibrations over a compact flat Riemannian 3-manifold Q. The flatness condition allows an explicit description of the deformation space of closed G2-structures, and hence also the moduli space of supersymmetric vacua: it is modeled by flat sections of a bundle of Brieskorn-Grothendieck resolutions over Q. Moreover, when instanton corrections are neglected, we obtain an explicit description of the moduli space for the dual type IIA string compactification. The two moduli spaces are shown to be isomorphic for an important example involving A1-singularities, and the result ...

Searching For Clean Observables In $B -> D* /Tau- \Bar{\Nu}_{\Tau}$ Decays, 2019 Virginia Commonwealth University

#### Searching For Clean Observables In $B -> D* /Tau- \Bar{\Nu}_{\Tau}$ Decays, Michael D. Williams Jr.

*Theses and Dissertations*

In this thesis, the clean angular observables in the $\bar{B} \to D^{*+} \ell^- \bar{\nu}_{\ell}$ angular distribution is studied. Similar angular observables are widely studied in $B \to K^* \mu^+ \mu^-$ decays. We believed that these angular observables may have different sensitivities to different new physics structures.

Symmetry Reduction In K − P Problems, 2019 Iowa State University

#### Symmetry Reduction In K − P Problems, Benjamin Sheller

*Graduate Theses and Dissertations*

$K-P$ problems are a class of geometric optimal control problems on finite-dimensional real semisimple Lie groups which arise, for example, in the control of quantum systems when the Lie group is $SU(n)$. In these problems, the sub-Riemannian distribution corresponds to the $\p$-part of a Cartan decomposition (also known as the $-1$ eigenspace of a Cartan involution), and these systems are totally controllable. However, finding a particular optimal trajectory can be in general a computationally difficult problem, and from an analytic perspective, the Lie groups are sufficiently complicated to make finding such objects as the cut locus difficult. $K-P ...