Join the Department of Physics and Astronomy on Wednesday, September 18 at 2:30pm in White Hall G09 for a colloquium presented by Ezekiel Johnston-Halperin (The Ohio State University). The title of the talk is, "Molecular Materials for Quantum Information Science and Engineering."  A reception will precede the colloquium at 2:00pm in White Hall 105.

Abstract

The rise of quantum information as a topic of combined fundamental and technological interest presents new challenges to the development of the electronic and photonic materials from which qubits are assembled. In addition to traditional challenges for these materials (defects, crystallinity, compatibility) they exhibit additional sensitivity to the quantum phase and coherence of the targeted degrees of freedom. In this context molecular materials are particularly appealing as they allow for atomic-scale manipulation of electronic, nuclear, and structural degrees of freedom that leverages decades (centuries?) of work in chemical synthesis. While this potential may seem academic given the apparent barriers to integrating molecular systems into the solid-state device architectures that dominate the quantum application space, I will discuss our recent demonstrations of the ability to utilize molecular materials for multiple applications that have traditionally been dominated by solid-state materials. For example, as a proof of concept we have developed the ability to deposit and pattern molecule-based thin films of the ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) that exhibit ultra-low damping under magnetic resonance (a ~ 4 x 10-5) and have been successfully integrated into high quality factor (high-Q) superconducting resonators, demonstrating strong microwave-magnon coupling [1]. Further, we have recently demonstrated a technique that allows for the encapsulation of molecular monolayers of the spin qubit vanadyl phthalocyanine (VOPc) within a solid-state tunnel junction constructed using exfoliation and stacking of the 2D materials graphene and hexagonal boronitride (hBN) [2]. These structures are sensitive to the electronic states of the VOPc, and the mechanical nature of the device assembly provides a platform that is general and modular – capable of measuring a wide variety of molecules as well as electrically active defects in 2D materials. Taken together, these advances point to a bright future for the development of novel quantum systems based on molecular materials that are directly competitive with their solid-state counterparts, with potential applications across the full spectrum of quantum information technologies, including sensing, communication, and computing.

• [1] Qin Xu, et al., Strong Photon-Magnon Coupling Using a Lithographically Defined Organic Ferrimagnet, Advanced Science, 2310032 (2024); https://doi.org/10.1002/advs.202310032
• [2] Marzieh Kavand, et al. “A general and modular approach to solid-state integration and readout of zero-dimensional quantum systems,” arXiv:2407.11189

Biography

Prof. Johnston-Halperin received his B.S. in physics from Case Western Reserve University in 1996, followed in 2003 by his Ph.D. in Physics at the University of California at Santa Barbara in the research group of Prof. David D. Awschalom in the area of semiconductor spintronics. His postdoctoral studies at the California Institute of Technology in the research group of Prof. James R. Heath extended from 2003 to 2006 and covered a number of projects ranging from nanostructured materials and sublithographic patterning to integrating molecular and solid-state materials to form extremely dense electronic circuits. He has been a faculty member in the Department of Physics at The Ohio State University since 2006 and has served as the co-Director of the Center for Quantum Information Science and Engineering at Ohio State since 2022. His research program exploits the ability to apply techniques and insights from one subfield of physics in the traditional wheelhouse of another. For example, one current focus is on exploring quantum coherent excitations of organic-based magnets and is informed by his prior work in exploring spin transport and magnetization dynamics in inorganic expitaxial ferromagnet/non-magnetic (FM/NM) heterostructures. In particular, he has been able to demonstrate coherent magnon states that demonstrate the lowest loss of any magnetic thin film developed to date, organic or inorganic. This remarkable discovery is driving much of his current work, as he explores the implications of this unprecedented coherence for applications ranging from non-reciprocal microwave electronics, to topologically protected magnon modes in artificially patterned magnon crystals, to use as a “quantum bus” to transduce between quantum computation and quantum communications in future quantum information systems (QIS). Parallel efforts that are currently at an earlier stage, but with similar long-term focus, include the demonstration of tunnel junctions based on mechanical exfoliation and stacking of 2D materials that can be used as a modular and general approach to studying 0D quantum systems (atoms, molecules, defects) encapsulated in the junctions.