Dr. Vlad Pribiag, UMN (STO Seminar)

Dr. Vlad Pribiag
Friday, March 26, 2021 - 3:00pm

Title: Magnetic properties of NdTiO3/SrTiO3 interfaces and broader implications

Abstract: SrTiO3-based thin-film heterostructures are a powerful platform for studying a wide array of electronic phases in two dimensions, at high carrier densities. I will discuss our low-temperature electronic transport studies of NdTiO3/SrTiO3 interfaces, which reveal an interplay between local ferromagnetic order, Kondo scattering and spin-orbit coupling. As the magnetic field angle is gradually tilted away from the sample normal,...

Dr. Beate Heinemann, DESY (Pitt/CMU Colloquium)

Dr. Beate Heinemann
Monday, March 22, 2021 - 4:00pm

A new experiment to study non-perturbative QED in electron-LASER and photon-LASER collisions

Abstract: The LUXE experiment (LASER Und XFEL Experiment) is a new experiment in planning at DESY Hamburg using the electron beam of the European XFEL. LUXE is intended to study collisions between a high-intensity optical LASER and 16.5 GeV electrons from the XFEL electron beam, as well as collisions between the optical LASER and high-energy secondary photons. The physics objective of LUXE are processes of Quantum Electrodynamics (QED) at the strong-field...

Quantum Bipartite Systems: Theory and Applications

Dr. Lu Wei
Tuesday, March 16, 2021 - 10:00am


Quantum information theory, a multi-disciplinary area of quantum physics, computer science, and mathematics, aims at understanding the theoretical underpinnings of quantum sciences that enables quantum computing and communications. Crucial to successful exploitation of the quantum revolutionary advances is the understanding of the non-classical phenomena of quantum entanglement. In this talk, we study the entanglement of quantum bipartite model and its applications to quantum information processing. 
In the first part of the talk, we discuss our...

Superconductivity in low-density Dirac materials

Dr. Vladyslav Kozii
Tuesday, March 2, 2021 - 4:00pm

The experimental observation of superconductivity in doped semimetals and semiconductors, where the Fermi energy is comparable to or smaller than the characteristic phonon frequencies, is not captured by the standard lore. In this talk, I present a mechanism for superconductivity in low-density three-dimensional Dirac materials that are close to a ferroelectric quantum critical point. I show that while the Coulomb repulsion between electrons is strongly screened by the lattice polarization near the critical point, the electron-phonon coupling is significantly...

"Quantum Advantage in Quantum-Limited Classical Optical Communications using NISQ Processors

Dr. Kaushik Seshadreesan
Thursday, March 4, 2021 - 10:00am

Demonstrating quantum advantage using near-term, noisy intermediate-scale quantum (NISQ) processors is a topic of keen interest in quantum computing. In laser communication systems that operate in the quantum-limited weak signal regime, such as deep-space optical communications, it has been rigorously proven that there exists a fundamental gap in terms of capacity and decoding error probability between conventional receivers that detect received modulated optical pulses one at a time, and "joint detection" receivers that collectively process optical pulse sequences (codeword blocks) in the...

Shedding Light on the Enigma of High Temperature Superconductivity in Monolayer FeSe / SrTiO3

Dr. Kyle Shen
Monday, March 1, 2021 - 4:00pm

Quantum materials host a vast array of emergent electronic phenomena, including high-temperature superconductivity, topological properties, and nanoscale charge / spin ordering. One of the challenges is to be able to precisely and deterministically manipulate their properties. To achieve this control, we employ molecular beam epitaxy (MBE) to synthesize artificial quantum materials with atomic layer precision, combined with angle-resolved photoemission spectroscopy (ARPES) which provides direct insights into the electronic structure. In particular, I will focus on...

Dr. Judy Wu, University of Houston (Pitt Chemistry Seminar)

Judy Wu
Thursday, February 25, 2021 - 2:30pm

Title: Molecules in a Hurry to Escape Antiaromaticity

Abstract: Antiaromatic molecules, unless kinetically trapped, fused to aromatic frameworks, or stabilized by chemical modifications, often are short-lived and difficult to work with experimentally—they always find ways of escaping the state of being called “antiaromatic.” Cyclobutadiene, cyclopentadiene, pentalene, and other cyclic, π-conjugated compounds, with formal [4n] ring π-electrons, easily dimerize to get rid of antiaromaticity. Upon irradiation, benzene rather isomerize to fulvene and...

Why Engineers Should Care about Quantum Computing -- From Quantum Hardware to Programming

Abraham Asfaw
Tuesday, February 9, 2021 - 11:00am

This talk will attempt to answer the question, "Why Should Engineers Care about Quantum Computation." In the talk, I will lay out key concepts and potential uses of quantum computers in quantum simulation and computation. As part of the discussion, I will emphasize the urgency of building a quantum-ready workforce, highlighting the relevance of training in engineering for building the physical quantum computing systems and understanding their potential applications. I will not assume knowledge of quantum mechanics and quantum computation, and will take a systems...

Dr. Moïra Hocevar, Institut Néel CNRS, France (CMU MSE Seminar)

Dr. Moïra Hocevar
Friday, April 2, 2021 - 11:30am

Growth of Nanowires Heterostructures for Quantum Devices and Nanotechnology

Abstract: Nanowires are crystals with the morphology of a hair but ten thousand times smaller. They measure several microns in length and tens of nanometers in diameter. For the past twenty years, nanowires have been at the root of important breakthrough in both basic science and nanotechnology in a multitude of scientific areas. They are now commonly developed for transistor and sensor applications, light emitting diodes or solar cells. In quantum technologies, their unique properties enabled the development of bright single photon sources, spin quantum bits and nanomechanical resonators. We fabricate nanowires with crystalline semiconductor materials such as silicon which is the backbone of electronics or gallium arsenide, which emits light and is used to manufacture light emitting diodes. For a certain number of applications, it is necessary to juxtapose different semiconductors to form a heterostructure. Yet, creating heterostructures is not an easy task, especially in thin films. As different crystalline materials have different lattice parameters (distance between atoms), the lattice is strained at the junction (or interface) between two materials. This induces the formation of defects, among them dislocations which deteriorate the targeted physical properties. Thanks to their morphology, nanowires have more flexibility to release strain, preventing the formation of defects. Nanowires have the potential to host heterostructures that cannot be fabricated in standard technologies, enabling the discovery of new physical phenomena and the improvement of existing devices. During the seminar, I will present an overview of my ongoing research on nanowire heterostructures. The first part will be dedicated to embedding light emitters in silicon technology. Different semiconductor families or high-mismatch semiconductors are combined in nanowires. I will show how interfaces are built without structural defects, a prerequisite for optoelectronic devices [1]. Then, I will present superconductor-semiconductor nanowire hybrids. A particular focus will be on the development and study of Sn/InSb interfaces which have recently shown high potential for superconducting and topological quantum circuits [2]. Finally, I will present the development of an ultrasensitive tool to study the mechanical properties of nanowires using a focused electron beam [3].

[1] Beznasyuk et al (2020)

[2] Pendharkar et al (2020)

[3] Pairis et al (2019)

Biography: Moïra Hocevar is a researcher at CNRS Néel Institute in Grenoble since January 2015. She received an Engineering degree in Materials Science from INSA de Lyon in France (2004), a master degree in Environmental Science from Université Denis Diderot in Paris (2005) and her PhD in Electronics from INSA de Lyon in 2008. Prior to joining Néel Institute in Grenoble, she was a Marie Curie postdoctoral fellow at the Technical University of Delft in the Netherlands and a Nanoscience Foundation postdoctoral fellow in Grenoble. Her research focuses on creating novel nanowire heterostructures by molecular beam epitaxy and uncovering their unique physical properties using Mhigh-end characterization tools.