Quantum Physics Commons^™

Formulation Of Causality-Preserving Quantum Time Of Arrival Theory, Denny Lane B. Sombillo, Neris I. Sombillo

Physics Faculty Publications

We revisit the quantum correction to the classical time of arrival to address the unphysical instantaneous arrival in the limit of zero initial momentum. In this study, we show that the vanishing of arrival time is due to the contamination of the causality-violating component of the initial wave packet. Motivated by this observation, we propose to update the temporal collapse mechanism in Galapon (2009) [18] to incorporate the removal of causality-violating spectra of the arrival time operator. We found that the quantum correction to the classical arrival time is still observed. Thus, our analysis validates that the correction is an …

Sensitive Capacitance Measurements Of The Quantum Hall Effect In Graphene, Vergil Schreiber, Justin Alvarez, Joshua Island

Undergraduate Research Symposium Podium Presentations

Research on how electrons respond to confinement holds potential for breakthroughs in quantum computing and more energy efficient electronics. In intense magnetic fields and near-zero temperatures, electrons in confined to 2D display unique quantum behaviors. These conditions quantize electron motion into circular orbits, resulting in discrete Landau energy levels.

Nuclear Charge Radius Determination Of Iridium Using Euv Spectroscopy Of Highly Charged Ions, Adam Hosier

All Dissertations

Highly charged ions have emerged on the scene of atomic physics because of their compressed electron cloud enhancing various physical phenomena. While transitions in ions and highly charged ions provide valuable information to different communities, their application in nuclear charge radius measurements becomes increasingly prominent. In this work, we report the extreme ultra-violet spectroscopy of Na-like ions and x-ray spectroscopy of Cu-like, Co-like, and Ni-like ions that explore nuclear charge distributions and the identification of new transitions, respectively.

In the first part of this work, extreme ultra-violet spectroscopy of highly charged ions of Na-like osmium and iridium was performed using …

Robust Zero Modes In Non-Hermitian Systems Without Global Symmetries, Jose D. H. Rivero, Courtney Fleming, Bingkun Qi, Liang Feng, Li Ge

Publications and Research

We present an approach to achieve zero modes in lattice models that do not rely on any symmetry or topology of the bulk, which are robust against disorder in the bulk of any type and strength. Such symmetry-free zero modes (SFZMs) are formed by attaching a single site or small cluster with zero mode(s) to the bulk, which serves as the “nucleus” that expands to the entire lattice. We identify the requirements on the couplings between this boundary and the bulk, which reveals that this approach is intrinsically non-Hermitian. We then provide several examples with either an arbitrary or structured …

Weak Measurements And Quantum-To-Classical Transitions In Free Electron–Photon Interactions, Yiming Pan, Eliahu Cohen, Ebrahim Karimi, Avraham Gover, Norbert Schönenberger, Tomáš Chlouba, Kangpeng Wang, Saar Nehemia, Peter Hommelhoff, Ido Kaminer, Yakir Aharonov

Mathematics, Physics, and Computer Science Faculty Articles and Research

How does the quantum-to-classical transition of measurement occur? This question is vital for both foundations and applications of quantum mechanics. Here, we develop a new measurement-based framework for characterizing the classical and quantum free electron–photon interactions and then experimentally test it. We first analyze the transition from projective to weak measurement in generic light–matter interactions and show that any classical electron-laserbeam interaction can be represented as an outcome of weak measurement. In particular, the appearance of classical point-particle acceleration is an example of an amplified weak value resulting from weak measurement. A universal factor, exp(-Γ²/2) , quantifies the …

Contributions Of Tunneling In 8Π-6Π Electrocyclic Cascade Reactions Of Bicyclo[4.2.0]Octa-2,4-Diene Moieties, Ishika Jain, Claire Castro, William L. Karney

Featured Student Work

Six-electron electrocyclic reactions usually require relatively high temperatures; however recent research has shown that such reactions can occur at significantly lower temperatures in biosynthetic and biomimetic pathways. Pathways resulting in bicyclo[4.2.0]octa-2,4-diene moieties arise from thermally allowed 8π-6π electrocyclization cascade reactions of 1,3,5,7-octatetraenes, as in the biosynthesis of endiandric acids, elysiapyrones, and numerous other natural products. We report multidimensional tunneling calculations to explore the possible contribution of heavy-atom tunneling (e.g. by carbon) to biosynthetic pathways and biomimetic syntheses, and thus to provide a more complete picture of biochemical kinetics. M06-2X/cc-pVDZ calculations on the 8π-6π cascade cyclizations of methylated octatetraene model systems …

Extended Defects And Linear Junctions At The Surfaces Of Topological Insulators, Eklavya Thareja

LSU Doctoral Dissertations

Topological Insulators (TIs) have emerged as promising candidates for spintronics and quantum computing applications. Two properties that underlie these applications are the locking of spin and momentum of the surface electrons and topological protection of surface states. While the existence of gapless surface states is guaranteed by topology, as long as time-reversal symmetry is intact, other properties of the surface states are still tunable. Spin-momentum locking makes these states immune to scattering from non-magnetic point impurities. However, extended defects can scatter the states even with electrostatic potential. We show that a line defect with magnetic and electrostatic potential scattering hosts …

Quantum Criticality At Cryogenic Melting Of Polar Bubble Lattices, Wei Luo, Alireza Akbarzadeh, Yousra Nahas, Sergei Prokhorenko, Laurent Bellaiche

Physics Faculty Publications and Presentations

Quantum fluctuations (QFs) caused by zero-point phonon vibrations (ZPPVs) are known to prevent the occurrence of polar phases in bulk incipient ferroelectrics down to 0 K. On the other hand, little is known about the effects of QFs on the recently discovered topological patterns in ferroelectric nanostructures. Here, by using an atomistic effective Hamiltonian within classical Monte Carlo (CMC) and path integral quantum Monte Carlo (PI-QMC), we unveil how QFs affect the topology of several dipolar phases in ultrathin Pb(Zr_0.4Ti_0.6)O₃ (PZT) films. In particular, our PI-QMC simulations show that the ZPPVs do not suppress polar …

Why Interference Phenomena Do Not Capture The Essence Of Quantum Theory, Lorenzo Catani, Matthew Leifer, David Schmid, Robert W. Spekkens

Mathematics, Physics, and Computer Science Faculty Articles and Research

Quantum interference phenomena are widely viewed as posing a challenge to the classical worldview. Feynman even went so far as to proclaim that they are the only mystery and the basic peculiarity of quantum mechanics. Many have also argued that basic interference phenomena force us to accept a number of radical interpretational conclusions, including: that a photon is neither a particle nor a wave but rather a Jekyll-and-Hyde sort of entity that toggles between the two possibilities, that reality is observerdependent, and that systems either do not have properties prior to measurements or else have properties that are subject to …

Tunneling Time And Faraday/Kerr Effects In Pt-Symmetric Systems, Peng Guo, Vladimir Gasparian, Antonio Antonio Perez-Garrido, Ester Jodar Ferrandez

Research & Publications

We review the generalization of tunneling time and anomalous behaviour of Fara- day and Kerr rotation angles in parity and time (PT )-symmetric systems. Similarities of two phenomena are discussed, both exhibit a phase transition-like anomalous behaviour in a certain range of model parameters. Anomalous behaviour of tunneling time and Faraday/Kerr angles in PT -symmetric systems is caused by the motion of poles of scattering amplitudes in the en- ergy/frequency complex plane.

Dynamics Of Spin And Charge Of Color Centers In Diamond Under Cryogenic Conditions, Richard G. Monge

Dissertations, Theses, and Capstone Projects

Individual quantum systems in semiconductors are currently the most sought-after platform for applications in quantum science. Most notably, the nitrogen-vacancy (NV) center in diamond features a defect deep within the electronic bandgap, making it amenable for precise manipulation to help pave the way to perform fundamental quantum physics experimentation. The NV center also offers long coherence times and versatile spin-dependent fluorescent properties, making it an ideal candidate for a nanoscale magnetometer. Furthermore, multi-color excitation offers deterministic charge state manipulation. While ambient operation has been key to their appeal, bringing NVs to cryogenic conditions opens new opportunities for alternate forms of …

Nonlinear Processes In Room Temperature Exciton-Polaritons, Prathmesh Deshmukh

Dissertations, Theses, and Capstone Projects

Strong light-matter coupling in solid state systems is an intriguing process that allows one to exploit the advantages of both light and matter. In this context, microcavities have become essential platforms for studying the strong coupling regime, where hybrid light-matter states known as exciton-polaritons form, leading to enhanced light matter interaction, modified material properties, and novel quantum phenomena. In this thesis, we explore the phenomenology of exciton-polaritons in strained TMD microcavities, 2D perovskites, fluorescent proteins and organic dyes encompassing thermalization, polariton lasing, and the observation of nonlinear effects.

Transition metal dichalcogenides (TMDs) have emerged as a remarkable class of two- …

Aspects Of The Phenomenology Of Interference That Are Genuinely Nonclassical, Lorenzo Catani, Matthew Leifer, Giovanni Scala, David Schmid, Robert W. Spekkens

Mathematics, Physics, and Computer Science Faculty Articles and Research

Interference phenomena are often claimed to resist classical explanation. However, such claims are undermined by the fact that the specific aspects of the phenomenology upon which they are based can in fact be reproduced in a noncontextual ontological model [Catani et al., arXiv:2111.13727]. This raises the question of what other aspects of the phenomenology of interference do in fact resist classical explanation. We answer this question by demonstrating that the most basic quantum wave-particle duality relation, which expresses the precise tradeoff between path distinguishability and fringe visibility, cannot be reproduced in any noncontextual model. We do this by …

Modifying The Composition Of A High Temperature Superconductor, Drue Lubanski

Electronic Theses and Dissertations

The purpose of this research was to recreate a known superconductor, YBa₂Cu₃O_x, and modify it in an attempt to raise its transition temperature. A superconductor is any material that excludes magnetic flux from its interior when at a temperature below its transition temperature. A “high temperature” superconductor refers to material that shows superconductivity at or above the temperature of liquid nitrogen temperatures (77.15K).

Here we were successful in reproducing the original YBa₂Cu₃O_x and measuring its critical temperature; However, our efforts at raising the transition temperature have, as of yet, …

Strong Ultrafast Demagnetization Due To The Intraband Transitions, G. P. Zhang, Mitsuko Murakami

Symposium Projects

Demagnetization in ferromagnetic transition metals driven by a femtosecond laser pulse is a fundamental problem in solid state physics, and its understanding is essential to the development of spintronic devices. Ab initio calculation of time-dependent magnetic moment in the velocity gauge so far has not been successful in reproducing the large amount of demagnetization observed in experiments. In this work, we propose a method to incorporate intraband transitions within the velocity gauge through a convective derivative in the crystal momentum space. Our results for transition-element bulk crystals (bcc Fe, hcp Co and fcc Ni) based on the time-dependent quantum Liouville …

Photon Counting Statistics Of Classical And Quantum Light Sources, Luis Felipe Morales Bultron

Graduate Theses and Dissertations

Multiple sources of light, including coherent light, thermal light, light from a degenerate parametric oscillation and resonance fluorescence from a two level coherently driven atom are considered for the analysis of their wait time statistics. We include the second order normalized correlation function and Mandel's Q parameter for brief discussion. A general framework to analyze the generalized conditional and unconditional wait time distributions is also obtained in order to understand the photo-count statistics of the light sources included in this work. Average and variance of wait times with respect to both unconditional and conditional wait time distribution are also obtained …

Super-Resolution Microscopy With Color Centers In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

This dissertation explores the development and application of diamond color centers, specifically the silicon-vacancy (SiV) and nitrogen-vacancy (NV) centers, in super-resolution microscopy and magnetic imaging techniques. It demonstrates the potential of SiV centers as photostable fluorophores in stimulated emission depletion (STED) microscopy, with a resolution of approximately 90 nm. The research also presents a method for nanoscale magnetic microscopy using NV centers by combining charge state depletion (CSD) microscopy with optically detected magnetic resonance (ODMR) to image magnetic fields produced by 30 nm iron-oxide nanoparticles. The individual magnetic feature width reaches ~100 nm while resolving magnetic field patterns from nanoparticles …

Entangled Photon Anti-Correlations Are Evident From Classical Electromagnetism, Ken Wharton, Emily Adlam

Mathematics, Physics, and Computer Science Faculty Articles and Research

For any experiment with two entangled photons, some joint measurement outcomes can have zero probability for a precise choice of basis. These perfect anti-correlations would seem to be a purely quantum phenomenon. It is, therefore, surprising that these very anti-correlations are also evident when the input to the same experiment is analyzed via classical electromagnetic theory. Demonstrating this quantum–classical connection for arbitrary two-photon states and analyzing why it is successful motivates alternative perspectives concerning entanglement, the path integral, and other topics in quantum foundations.

Nonlinear Charge And Spin Currents In Non-Centrosymmetric Electron Systems, Aniruddha Pan

All Dissertations

In this thesis, we discuss the existence of spin and charge currents in systems with broken spin inversion symmetry proportional to the magnitude square of the driving electric and thermal fields. This outcome is predicated on symmetry considerations in the momentum space, whereby the product between the current operator and the out-of-equilibrium distribution function has to be even.

First, we derive the second-order correction to the particle distribution function $\delta f^{(2)}$ in a semi-classical approximation, considering the local change in the equilibrium distribution function caused by external fields. Our approach departs significantly from the previous theory where $\delta f^{(2)}$ is …

Conservation Laws And The Foundations Of Quantum Mechanics, Yakir Aharonov, Sandu Popescu, Daniel Rohrlich

Mathematics, Physics, and Computer Science Faculty Articles and Research

In a recent paper, [Y. Aharonov, S. Popescu, D. Rohrlich, Proc. Natl. Acad. Sci. U.S.A.118 e1921529118 (2021)], it was argued that while the standard definition of conservation laws in quantum mechanics, which is of a statistical character, is perfectly valid, it misses essential features of nature and it can and must be revisited to address the issue of conservation/nonconservation in individual cases. Specifically, in the above paper, an experiment was presented in which it can be proven that in some individual cases, energy is not conserved, despite being conserved statistically. It was felt however that this is worrisome and …