Chithresh’s work addresses what limits the lifetime of a spin state in a solid host. A defect spin used as a quantum bit loses phase coherence primarily through coupling to the surrounding nuclear-spin bath via hyperfine interactions. The resulting coherence time T₂ is therefore constrained by host isotopics and the spatial distribution of nuclear spins around the defect.

He combines density functional theory with linear-response Hubbard corrections (DFT+U), all-electron projector-augmented-wave hyperfine reconstructions, and Green’s-function coherent potential approximation (KKR-CPA) methods to compute the electronic, vibrational, and exchange properties that govern spin relaxation channels.

In cerium dioxide (CeO₂), he examines rare-earth spin centres formed when native oxygen vacancies donate electrons that localise as Ce³⁺ (4f¹, S = 1/2) small polarons. Because every stable cerium isotope is nuclear-spin-free (I = 0), the magnetic bath is carried entirely by dilute ¹⁷O (0.038% natural abundance). His calculations show that this bath is further thinned by orbital symmetry: transferred spin density follows the lobe structure of the single occupied 4f orbital rather than the coordination polyhedron, placing only one oxygen per polaron in a strongly coupled tier (~5.5 MHz Fermi-contact coupling) while leaving outer nuclei weakly coupled and inter-polaron exchange negligible. These tensors provide the microscopic bath parameterisation required for cluster-correlation-expansion (CCE) modeling of spin coherence.