@article{Addressable:3604,
      recid = {3604},
      author = {Kovos, Berk Diler},
      title = {Transition Metal Ions as Optically Addressable Spin  Qubits},
      publisher = {The University of Chicago},
      school = {Ph.D.},
      address = {2021-12},
      pages = {232},
      abstract = {This thesis investigates transition metal ions (TMIs) as  an emerging platform to create quantum bits (qubits). The  electronic orbitals of TMIs can be tuned and designed using  basic guiding principles to form various structures that  contain long lived qubits in the ground state and spin  selective optical transitions that form a photonic  interface to initialize and readout the quantum  states.

This thesis starts with describing the physics  behind electron spin qubits and TMI orbitals that host the  electrons. We then narrow the focus to a few symmetry  configurations based on basic design principles from  understanding TMI physics. Through optical spectroscopy we  confirm the expected electronic structure that allows for a  spin-photon interface of chromium ions within two different  semiconducting hosts: silicon carbide (SiC) and gallium  nitride (GaN). We observe a striking similarity of the  optical and spin structure between the qubits in these  different semiconducting hosts. This is a result of the  similar local environment of the defects, demonstrating the  portability of TMI qubits across various hosts. We then  further narrow our focus to TMI qubits within SiC, a  technologically mature semiconducting material widely used  in industry. We create qubits in this material on demand  through ion implantation and annealing, a first step  towards scalable quantum devices based on transition metal  qubits within solid state. In this system, we show long  spin lifetimes for ensembles of chromium ions with high  optical initialization and readout fidelities, which  demonstrates their viability as spin qubits with optical  addressability. We also characterize vanadium ion defect  spins that possess an optical interface within the telecom  O-band compatible with single-ion detection, showing  promise for using them in long distance quantum  communication devices that can utilize the existing  low-loss telecommunications fiberoptic infrastructure.  Finally, we leverage a new synthetic chemistry approach to  atomistically design the local ligand environment of TMIs  to generate optically addressable molecular spin qubits and  show their coherent control. By changing the ligand  environment and/or the core transition metal type, we can  keep the physics of the qubit the same while changing both  the optical transition over 200 nm and the microwave  transitions over 100 GHz, showing the promise of transition  metal based molecules as tailor-made qubits for different  quantum applications that can range from self-assembled  individually addressable spin arrays for quantum  computation to highly multiplexed quantum sensors that are  a nanometer in size.

The demonstrations of long coherence  times with high initialization and readout fidelities,  detection of single emitters within the telecom band, and  synthetically tunable molecular qubits highlight the  promise of TMIs as a flexible, emerging quantum technology  platform with potential applications in quantum  communication, computation, and sensing.},
      url = {http://knowledge.uchicago.edu/record/3604},
      doi = {https://doi.org/10.6082/uchicago.3604},
}