New Fun with the Quantum Nuclei

We have developed the first ab initio computational method to calculate the temperature shift of spin-transition energies (zero-field splitting, hyperfine interaction, nuclear quadrupole interaction) and zero phonon line (ZPL) in lattice defects such as the nitrogen-vacancy center in diamond. [J. Phys. Chem. Lett. 14 (2023) 3266] Supported by these computational predictions, Cappellaro group has shown that the temperature and strain variations in point-defect qubit ensembles can be largely filtered out in an “unbalanced spin echo” protocol, demonstrating a 20-fold increase in the dephasing time in an ensemble of 10^10 nuclear spins in diamond and robust quantum coherence protection. [ PRL 131 (2023) 043602; PNAS 120 (2023) e2305621120 ] We have also developed a theory called optonuclear quadrupolar (ONQ) effect [Physical Review X 13 (2023) 011017], where two photons (100 THz and above) are used to manipulate nuclear spins that typically evolve at much slower (~MHz) timescales. The ONQ effect has been scoped for potential applications in laser cooling of nuclear magnons [PRL 130 (2023) 063602], quantum memory, microwave-to-optical quantum transduction, isotope spectroscopy, and for inducing population inversion between the isomeric and ground state of 229Th (8.3 eV) that could lead to gamma-ray laser, using a Watt-scale UV-B pumping laser and ultrawide bandgap thorium compound gain medium [PRA 108 (2023) L021502].