Investigation of the clock transition and its pressure-dependent behavior of the trigonal 171Yb3+ centers in lithium niobate crystal.

The application of rare earth (RE) doped crystals in quantum information processing has attracted more and more attention in the past decade. How to change the clock transitions of RE ion in crystal and control their lifetime of maintaining coherent quantum state is a valuable question. In this work, the trigonal ¹⁷¹Yb³⁺ centers in lithium niobate (LN) crystal are investigated theoretically to obtain their accurate ground and excited hyperfine sublevels under external magnetic field B by a combined method of density functional theory-based geometric optimization and parametric effective Hamiltonian modeling. An optical clock transition at |B| = 45.73 mT along the c axis of the LN crystal is successfully found by calculation. To show the pressure-dependent behavior of optical clock transition, the variation of such transition under hydrostatic pressure up to 3 GPa is also obtained theoretically. The calculated results show that applying external pressure is an effective way to control these transitions of RE ion doped crystal. Moreover, the optical coherence time T₂ at zero magnetic field for ¹⁷¹Yb³⁺ ion with C₃ symmetry in the LN crystal is estimated by our calculations. The calculated results indicate that if the magnetic field noise is 33 μT in the LN crystal, it is possible to find an optical clock transition with long coherence time T₂ (≈382 μs) at the zero magnetic field. The present methods of seeking optical clock transition and calculating its coherence time T₂ caused by a fluctuating magnetic field noise in the host crystal can be applied to other Kramers RE ions doped materials. [ABSTRACT FROM AUTHOR]