Quantum Physics Commons^™

Non-Gaussian Measurements Of Coherent States Of Light For Metrology And Communication, Matthew Dimario

Physics & Astronomy ETDs

Conventional measurement technology is unable to extract the most amount of information possible from coherent states of light. Non-Gaussian measurements which can count individual photons can surpass the sensitivity limits of ideal conventional strategies, and approach the ultimate limits achievable given by quantum mechanics. This thesis presents investigations and demonstrations of these unconventional measurements, which utilize coherent operations and single photon counting. This thesis shows that non-Gaussian measurements can outperform conventional strategies in estimation tasks as well as a variety of communication problems. This thesis also investigates novel approaches and algorithms for building robustness to static and dynamic noise which …

Radial Basis Densities And The Density Functional-Based Atom-In-Molecule: Designing Charge-Transfer Potentials, Godwin Amo-Kwao

Nanoscience and Microsystems ETDs

Classical potentials that are capable of describing charge transfer and charge polarization in complex systems are of central importance for classical atomistic simulation of biomolecules and materials. Current potentials—regardless of the system—do not generalize well, and, with the exception of highly-specialized empirical potentials tuned for specific systems, cannot describe chemical bond formation and breaking. The charge-transfer embedded atom method (CT-EAM), a formal, DFT-based extension to the original EAM for metals, has been developed to address these issues by modeling charge distortion and charge transfer in interacting systems using pseudoatom building blocks instead of the electron densities of isolated atoms. CT-EAM …

On The Complexity Of Boson Sampling Using Atoms In Optical Lattices, Gopikrishnan Muraleedharan

Physics & Astronomy ETDs

The extended Church-Turing thesis says that any computation that can be done by a physically realizable model of computers can be efficiently computed by the simplest model of classical computer, a Turing machine. Since the introduction of the concept of quantum computers, a central goal has been to find instances where the extended Church- Turing thesis fails. In the current noisy intermediate-scale quantum devices era, one looks for such instances that can be simulated on modest devices of small scale in the presence of noise. In this thesis, we work with one such problem, namely the Boson Sampling problem. We …

Measurement And Control For Quantum State Tomography, State Preparation, And Metrology, Ezad Shojaee Mr.

Physics & Astronomy ETDs

Quantum information science can deliver its promises in technology if we have access to near-perfect quantum states, quantum channels, and readout. These are the building blocks of any quantum informatics in computation, communication, and simulation. Invasiveness of quantum measurement is one of the major challenges in this realm. The fact that after a measurement the quantum state changes is now a rule of the game. We need smart ways to gain information about a quantum state, given finite resources, in order to characterize it prior to any task.

In this dissertation, we realize the optimal way to do quantum state …

Quantum Algorithms With Applications To Simulating Physical Systems, Anirban Ch Narayan Chowdhury

Physics & Astronomy ETDs

The simulation of quantum physical systems is expected to be an important application for quantum computers. The work presented in this dissertation aims to improve the resource requirements of quantum computers for solving simulation problems, by providing both novel quantum algorithms and improved implementations of existing ones. I present three main results that cover diverse aspects of simulation including equilibrium physics, the preparation of useful quantum states, and simulations based on classical stochastic processes. The results rely on established quantum algorithms and other recent techniques which I review. My first original contribution is a new quantum algorithm to sample from …

Topics In Three-Dimensional Imaging, Source Localization And Super-Resolution, Zhixian Yu

Physics & Astronomy ETDs

The realization that twisted light beams with helical phasefronts could carry orbital angular momentum (OAM) that is in excess of the photon's spin angular momentum (SAM) has spawned various important applications. One example is the design of novel imaging systems that achieve three-dimensional (3D) imaging in a single snapshot via the rotation of point spread function (PSF).

Based on a scalar-field analysis, a particular simple version of rotating PSF imagery, which was proposed by my advisor Dr. Prasad, furnishes a practical approach to perform 3D source localization using a spiral phase mask that generates a combination of Bessel vortex beams. …

Improving The Readout Of Semiconducting Qubits, Matthew Jon Curry

Physics & Astronomy ETDs

Semiconducting qubits are a promising platform for quantum computers. In particular, silicon spin qubits have made a number of advancements recently including long coherence times, high-fidelity single-qubit gates, two-qubit gates, and high-fidelity readout. However, all operations likely require improvement in fidelity and speed, if possible, to realize a quantum computer.

Readout fidelity and speed, in general, are limited by circuit challenges centered on extracting low signal from a device in a dilution refrigerator connected to room temperature amplifiers by long coaxial cables with relatively high capacitance. Readout fidelity specifically is limited by the time it takes to reliably distinguish qubit …

Towards Scalable Characterization Of Noisy, Intermediate-Scale Quantum Information Processors, Travis Luke Scholten

Physics & Astronomy ETDs

In recent years, quantum information processors (QIPs) have grown from one or two qubits to tens of qubits. As a result, characterizing QIPs – measuring how well they work, and how they fail – has become much more challenging. The obstacles to characterizing today’s QIPs will grow even more difficult as QIPs grow from tens of qubits to hundreds, and enter what has been called the “noisy, intermediate-scale quantum” (NISQ) era. This thesis develops methods based on advanced statistics and machine learning algorithms to address the difficulties of “quantum character- ization, validation, and verification” (QCVV) of NISQ processors. In the …

Plasmon-Enhanced Quadrupolar Transitions With Nanostructured Graphene, Stephen Sanders

Shared Knowledge Conference

Many important molecules have quadrupolar excitations which occur at much slower rates than the competing dipolar transitions and hence are termed forbidden. In this work, we propose a new approach to enhance quadrupolar transitions using graphene nanostructures. We provide a detailed investigation of the enhanced transition rate in the vicinity of graphene nanoislands and use rigorous computational methods to analyze how this quantity changes with the geometrical and material parameters of the nanoisland. To support these calculations we also provide a semi-analytic approach. Finally, we investigate the performance of arrays of graphene nanoribbons, which constitutes a suitable platform for the …

Sampling Complexity Of Bosonic Random Walkers On A One-Dimensional Lattice, Gopikrishnan Muraleedharan, Akimasa Miyake, Ivan Deutsch

Shared Knowledge Conference

Computers based quantum logic are believed to solve problems faster and more efficiently than computers based on classical boolean logic. However, a large-scale universal quantum computer with error correction may not be realized in near future. But we can ask the question: can we devise a specific problem that a quantum device can solve faster than current state of the art super computers? One such problem is the so called "Boson Sampling" problem introduced by Aaronson and Arkhipov. The problem is to generate random numbers according to same distribution as the output number configurations of photons in linear optics. It …

Weak Measurements For Quantum Characterization And Control, Jonathan A. Gross

Physics & Astronomy ETDs

This dissertation concerns itself with the virtues and vices of weak measurements. Weak measurements are all around us, but this does not mean that one should manufacture weakness on all occasions. We critically evaluate two proposals that claim weak measurements provide a novel means of performing quantum state tomography, allegedly increasing tomographic efficacy and yielding foundational insights into the nature of quantum mechanics. We find weak measurements are not an essential ingredient for most of their advertised features. In contrast to this negative finding, we highlight an optimal tomographic scheme for which weak continuous measurements are the best known implementation, …

Localization And Scrambling Of Quantum Information With Applications To Quantum Computation And Thermodynamics, Adrian Kristian Chapman

Physics & Astronomy ETDs

As our demand for computational power grows, we encounter the question: "What are the physical limits to computation?" An answer is necessarily incomplete unless it can incorporate physics at the smallest scales, where we expect our near-term high-performance computing to occur. Microscopic physics -- namely, quantum mechanics -- behaves counterintuitively to our everyday experience, however. Quantum matter can occupy superpositions of states and build stronger correlations than are possible classically. This affects how quantum computers and quantum thermodynamic engines will behave.

Though these properties may seem to overwhelmingly defeat our attempts to build a quantum computer at-first-glance, what is remarkable …

On Maxwell-Dirac Isomorphism, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

No abstract provided.

Dispersive Quantum Interface With Atoms And Nanophotonic Waveguides, Xiaodong Qi

Physics & Astronomy ETDs

Strong coupling between atoms and light is critical for quantum information processing and precise sensing. A nanophotonic waveguide is a promising platform for realizing an atom-light interface that reaches the strong coupling regime. In this dissertation, we study the dispersive response theory of the nanowaveguide system as the means to create an entangling atom-light interface, with applications to quantum non-demolition (QND) measurement and spin squeezing.

We calculate the dyadic Green's function, which determines the scattering of light by atoms in the presence of a nanowaveguide, and thus the phase shift and polarization rotation induced on the guided light. The Green's …

Vibrational Relaxation Theory For Systems Embedded In Microscopically Specified Reservoirs, Anastasia Aemilia Ierides

Physics & Astronomy ETDs

This dissertation is a study of the theoretical framework of the practical as well as fundamental problem of the process of relaxation to equilibrium of quantum mechanical systems. The fundamental aspect is concerned with the simultaneous occurrence of decoherence and population equilibration. The practical aspect deals with experimental observations of vibrational relaxation of molecules embedded in liquids or solids. The systems include, but are not limited to, the nondegenerate dimer and harmonic oscillator, in one case weak and in the other strong, interaction with a thermal bath. The time dependence of the energy and the temperature dependence of the relaxation …

Studies Of Light Generation With Four-Wave Mixing In A Cold Atomic Ensemble, Andrew Ferdinand

Physics & Astronomy ETDs

Correlated light generated from atomic ensembles can have a central role in prominent quantum information protocols, such as long-distance quantum communication. Here we present our studies on three topics involving the generation of correlated light with four-wave mixing (FWM) in a cold atomic ensemble for applications in quantum communications with high capacity. We experimentally investigate the generation of light with seeded FWM in cold cesium atoms and the time correlations of photon pairs generated with spontaneous FWM. We theoretically investigate the correlations in orbital angular momentum of photon pairs generated with spontaneous FWM for a range of experimental geometries. These …

On Syntropy & Precognitive Interdiction Based On Wheeler-Feynman’S Absorber Theory, Florentin Smarandache, Victor Christianto, Yunita Umniyati

Branch Mathematics and Statistics Faculty and Staff Publications

It has been known for long time that intuition plays significant role in many professions and human life, including in entrepreneurship, government, and also in detective or law enforcement activities. Women are known to possess better intuitive feelings or “hunch” compared to men. Despite these examples, such a precognitive interdiction is hardly accepted in established science. In this letter, we discuss briefly the advanced solutions of Maxwell equations, and then explore plausible connection between syntropy and precognition.

Measurement-Based Quantum Computation And Symmetry-Protected Topological Order, Jacob E. Miller

Physics & Astronomy ETDs

While quantum computers can achieve dramatic speedups over the classical computers familiar to us, identifying the origin of this quantum advantage in physical systems remains a major goal of quantum information science. A useful tool here is measurement-based quantum computation (MQC), a computational framework utilizing the quantum entanglement found in many-body resource states. Not all resource states are useful for quantum computation however, so an important question is what properties of many-body entanglement characterize universal resource states, which can implement any quantum computation.

Many-body states are also studied in condensed matter physics, where the collective behavior of quantum many-body systems …

Quantum Quasi-Paradoxes And Quantum Sorites Paradoxes, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

There can be generated many paradoxes or quasi-paradoxes that may occur from the combination of quantum and non-quantum worlds in physics. Even the passage from the micro-cosmos to the macro-cosmos, and reciprocally, can generate unsolved questions or counter-intuitive ideas. We define a quasi-paradox as a statement which has a prima facie self-contradictory support or an explicit contradiction, but which is not completely proven as a paradox. We present herein four elementary quantum quasi-paradoxes and their corresponding quantum Sorites paradoxes, which form a class of quantum quasi-paradoxes.