# Lecture Videos

Dr. Mario Hofmann and Dr. Ya-Ping Hsieh from the National Taiwan University and Academia Sinica gave a talk titled "Why and How to Integrate 2D Materials in Future Electronics" in the Pittsburgh Quantum Institute Fall Seminar series on Nov. 17th, 2020.

**Abstract**: 2D materials are atomically thin nanostructures that are considered enabling elements in future electronics due to their unique geometry and exciting physical properties. To realize such applications, however, challenges in materials quality and production have to be addressed. In this talk we will first introduce a novel growth method that can enhance the scale, reliability, and controllability of 2D materials synthesis. Through control of the gas phase kinetics of the chemical vapor deposition process, efficient 2D materials growth could be achieved in atomically confined conditions. This advance permits the synthesis of 2D materials, such as graphene and TMDCs, at unprecedented scale and at crystalline qualities that rival exfoliated materials. Moreover, synthesis in the van-der-Waals gap of a host 2D material is demonstrated to facilitate a novel 2D crystallization process that yields novel transition-metal monochalcogenides with unexpected thermodynamic properties and finely adjustable thickness. Finally, the atomic length scales in confined growth enable controllable multi-precursor synthesis of diluted magnetic semiconductor 2D materials. The high quality of thus grown materials reveal novel interfacial ordering effects of 2D materials that are fundamentally different from bulk and present both challenges and opportunities towards their integration in electronics. Organization of ionic impurities on high quality graphene was shown to introduce a novel scattering process, that modulates graphene’s mobility by six times and is independent of charge concentration, necessitating improvements in materials’ characterization and handling. On the other hand, ordering effects at 2D materials interfaces can provide routes towards enhanced fabrication and performance of electronic devices. Interaction of graphene surfaces with gaseous adsorbates was shown to stabilize graphene in chemical reactions, permitting atomic-precision lithography approaches for large-scale semiconductor fabrication. Finally, assembly of monolayer water films on graphene under nanomechanical confinement was shown to produce a novel ferroelectric ice phase that can be exploited in mechanical memristive devices.

Dr. Dave Wallace from the University of Pittsburgh gave a talk titled "What is 'Orthodox' Quantum Mechanics?" in the Pittsburgh Quantum Institute Fall Seminar series on Nov. 12th, 2020.

Abstract: What is called "orthodox'' quantum mechanics, as presented in standard foundational discussions, relies on two substantive assumptions --- the projection postulate and the eigenvalue-eigenvector link --- that do not in fact play any part in practical applications of quantum mechanics. I argue for this conclusion on a number of grounds, but primarily on the grounds that the projection postulate fails correctly to account for repeated, continuous and unsharp measurements (all of which are standard in contemporary physics) and that the eigenvalue-eigenvector link implies that virtually all interesting properties are maximally indefinite pretty much always. I present an alternative way of conceptualizing quantum mechanics that does a better job of representing quantum mechanics as it is actually used, and in particular that eliminates use of either the projection postulate or the eigenvalue-eigenvector link, and I reformulate the quantum measurement problem within this new presentation of orthodoxy.

Dr. Chris Lirakis from IBM-Q gave a talk titled "What does it Take to Build a Quantum Computer" in the Pittsburgh Quantum Institute Fall Seminar series on Oct. 1st, 2020.

Abstract: IBM has been working on realizing a quantum computer since the idea first surfaced in 1982. Early instantiations were photon-based and proved that indeed bit like information could be stored in a quantum state. Since then many different modalities have sprung up, Trapped Ions and Superconducting qubits being the most popular. The IBM systems are on the path to error correction. However, we still have a long way to go. The path to success will be paved by wide scale acceptance and training in these using this new computational paradigm. All manner of expertise will be important on the road to success. Beyond the need for experts in quantum computation, the nation will need experts in mechanical engineering, electrical engineering, computer science and other disciplines. During this talk I will show how IBM is using superconducting technology as quantum bits (qubits) and all of the ancillary technology along with notions of the types of problems we wish to solve. The goal is to show how each of this disciplines can help on the path to large scale system.

Dr. Paul Ohodnicki from the University of Pittsburgh gave a talk titled "Energy Infrastructure Sensing Technologies and Opportunities for Quantum" in the Pittsburgh Quantum Institute Fall Seminar series on Sept. 24th, 2020.

Abstract: An overview will be presented of some emerging platforms that are relevant for energy infrastructure sensing applications including both optical fiber and passive wireless technologies. Example motivating applications will be presented including grid modernization, energy resource recovery and transport, and power generation, along with an overview of existing and future sensing technologies under investigation. A specific emphasis will be placed upon opportunities and limitations in such applications for quantum materials and quantum sensing concepts to enhance capabilities of current and emerging technology platforms, as well as to realize new capabilities which would not be otherwise possible.

Dr. Venkat Gopalan from Pennsylvania State University gave a talk titled "Antisymmetry: Fundamentals and Applications" in the Pittsburgh Quantum Institute Fall Seminar series on Sept. 17th, 2020.

Abstract: Symmetry is fundamental to understanding our physical world. An antisymmetry operation switches between two different states of a trait, such as two time-states, position-states, charge-states, spin-states, chemical-species etc. This talk will cover the fundamental concept of antisymmetry, with brief mentions of two well-established antisymmetries, namely spatial inversion in point groups and time reversal. Then it will introduce two new ones, namely, distortion reversal and wedge reversion. The distinction between classical and quantum mechanical descriptions of time reversal will be discussed. Applications of these antisymmetries will be presented such as crystallography, property tensors, transition state theory, magnetic structures, ferroelectric and multiferroic switching, and classifying physical quantities in arbitrary dimensions.

Dr. Arthur Davidson, retiree from Carnegie Mellon University, gave a talk titled "Rings and tunnel junctions: Quantum mechanics on a circle" in the Pittsburgh Quantum Institute Fall Seminar series on Sept. 10th, 2020.

Abstract: We show by standard quantum principles that two circuits, a small tunnel junction and a small metal loop with an electron, are related by a gauge transformation. We show further that this same transform prevents momentum eigen functions from having gauge invariant de Broglie wave lengths around a ring. Thus persistent current on a metal ring and the Coulomb blockade on a small tunnel junction seem to be the same dynamical theory based on discontinuous Bloch waves on the perimeter of a circle. This is historically an area of simple quantum circuits where the principle of gauge invariance has not been applied. It is remarkable that some of these circuits are of intense current interest as candidates for qubit circuits for quantum computers.

Dr. Jim Freericks from Georgetown University gave a talk titled "Operator Mechanics: A new form of quantum mechanics without waves or matrices" in the Pittsburgh Quantum Institute Fall Seminar series on Sept. 3rd, 2020.

His presentation slides can be found here: https://drive.google.com/drive/folders/1zLohpkcooZx7fPrht0gZOfWvBg9Ja34B

**Abstract**: Quantum mechanics was created with the matrix mechanics of Heisenberg, Born, and Jordan. Schroedinger's wave mechanics shortly followed and allowed for simpler and more powerful calculations. Both Pauli and Dirac introduced a formulation of quantum mechanics based on operators and commutation relations, but it was never fully developed in the 1920's. Instead, Schroedinger formulated the operator approach with his factorization method, which later was adopted by the high-energy community as supersymmetric quantum mechanics. In this talk, I will explain how one can formulate nearly all of quantum mechanics algebraically by a proper use of the translation operator on top of Schroedinger's factorization method. I will give examples of how one can compute spherical harmonics algebraically, how one can find harmonic oscillator wavefunctions, and will even describe an operator-based derivation of the wavefunctions of Hydrogen. I will end with a proposal for a novel way to teach quantum mechanics, focusing first on conceptual ideas related to superposition, projective measurements, and entanglement. Then developing more conventional topics like spin, harmonic oscillator, angular momentum, interacting spin models, central potentials, particles in a box and so on. This is the subject of a book in progress entitled Quantum Mechanics without Calculus.

This week's focus is on quantum computing and we are pleased to be joined by our featured speaker, So Hirata from UI Urbana-Champaign. Rongchao Jin was unable to join due to unforeseen circumstances.

So Hirata, UIUC, “Numerical Evidence Invalidating Textbook Finite-Temperature Perturbation Theory”

This week's focus is on quantum materials and we are pleased to be joined by our featured speaker, Chris Van de Walle from UC Santa Barbara, and PQI member contributing speaker, Linda Peteanu from CMU.

Linda Peteanu (CMU) "Probing Single- and Bi-excitonic States in Silicon Nanoparticles"

Chris Van de Walle, UCSB, “Modeling Point Defects for Quantum Information Science”

This weeks focus is on quantum optics and we are pleased to be joined by our featured speaker, Dan Stamper-Kurn from UC Berkeley, and PQI member contributing speakers, Andrew Daley from the University of Strathclyde and Tom Purdy from Pitt.

Andrew Daley (UStrathclyde), “Reaching practical quantum advantage in quantum simulation”

Dan Stamper-Kurn (UC Berkeley) “Using Light to Measure and Control Quantum Systems"

Tom Purdy (Pitt), "The Quantum Optical Level”