| Popis: |
Quantum information science and engineering requires novel low-loss magnetic materials for magnon-based quantum-coherent operations. The search for low-loss magnetic materials, traditionally driven by applications in microwave electronics near room-temperature, has gained additional constraints from the need to operate at cryogenic temperatures for many applications in quantum information science and technology. Whereas yttrium iron garnet (YIG) has been the material of choice for decades, the emergence of molecule-based materials with robust magnetism and ultra-low damping has opened new avenues for exploration. Specifically, thin-films of vanadium tetracyanoethylene (V[TCNE]x) can be patterned into the multiple, connected structures needed for hybrid quantum elements and have shown room-temperature Gilbert damping (α = 4 x 10^(-5)) that rivals the intrinsic (bulk) damping otherwise seen only in highly-polished YIG spheres (far more challenging to integrate into arrays). However, while these properties clearly establish the potential of V[TCNE]x for new applications in traditional microwave electronics, very little is known about its low-temperature magnetization dynamics and therefore its potential for applications in quantum information science and technology. Presented in this thesis a comprehensive and systematic study of the low-temperature magnetization dynamics for V[TCNE]x thin films, with implications for their application in quantum systems. These studies reveal a temperature-driven, strain-dependent magnetic anisotropy that compensates the thin-film shape anisotropy, and the recovery of a magnetic resonance linewidth at 5 K that is comparable to room-temperature values (roughly 2 G at 9.4 GHz). We can account for these variations of the V[TCNE]x linewidth within the context of scattering from very dilute paramagnetic impurities, and anticipate additional linewidth narrowing as the temperature is further reduced. Additionally, ongoing work investigating quantum-to-quantum transduction via spin-magnon coupling between nitrogen vacancy (NV) centers in diamond and magnons in V[TCNE]x are discussed. Here we outline the theoretical confirmation for available magnon modes in V[TCNE]x that can couple to NV spins with cooperativity Cλ of ≈ 15 We also within a wide spatial area within the diamond substrate, sufficiently far below the surface to avoid uncontrolled surface spin noise, thus making our proposal experimentally realizable and not sensitively dependent on the NV center position. Backed up by promising theory work, we also discuss the significant progress towards experimental realization of NV spin-magnon coupling. |
