Extension of orbital lifetimes of silicon-vacancy centers in diamond using phononic crystals

Silicon-vacancy (SiV) centers in diamond are promising solid-state quantum emitters for various quantum photonic applications because of their strong and stable zero phonon line emission and optically accessible spin. However, their spin coherence time is short at 4K, mainly limited by phonon transitions between ground-state orbital branches. In this work, we demonstrate suppression of the phonon transitions by using phononic crystals (PnCs) to control the phonon density of states. We fabricate free-standing 1D PnCs with a complete phononic bandgap using a quasi-isotropic etching technique on single-crystal diamond. We observe a more than ten-fold increase in orbital lifetimes for single SiVs embedded in PnCs compared to SiVs in bulk, with values of up to 500 ns. This result demonstrates the potential of PnCs to control emitter-phonon interactions and paves the way for developing quantum network nodes using SiV centers in PnCs.