Molecular Materials for Quantum Information Science and Engineering

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.