We demonstrate heralded initialization of charge state and optical transition frequency of diamond tin-vacancy centers, using (off-)resonant lasers, photon detection and real-time logic. Using this, we show frequency tunability > 100 MHz and strongly improved optical coherence.

Diamond tin-vacancy centers have emerged as a promising platform for quantum information science and technology. A key challenge for their use in more-complex quantum experiments and scalable applications is the ability to prepare the center in the desired charge state with the optical transition at a predefined frequency. Here we report on heralding such successful preparation using a combination of laser excitation, photon detection, and real-time logic. We first show that fluorescence photon counts collected during an optimized resonant probe pulse strongly correlate with the subsequent charge state and optical-transition frequency, enabling real-time heralding of the desired state through threshold photon counting. We then implement and apply this heralding technique to photoluminescence-excitation measurements, coherent optical driving, and an optical Ramsey experiment, finding strongly increased optical coherence with increasing threshold. Finally, we demonstrate that the prepared optical frequency follows the probe laser across the inhomogeneous linewidth, enabling tuning of the transition frequency over multiple homogeneous linewidths.

We present our optimized diamond fabrication process based on quasi-isotropic crystal-plane-dependent reactive-ion-etching at low and high temperature plasma regime. We demonstrate successful integration of SnV centers in diamond waveguides showing quantum non-linear effects. We report on our latest results on all-diamond photonic crystal cavities.

We show coupling of an SnV center to a diamond waveguide of 20% with almost transform-limited optical transitions. Besides, we show control over the SnV spin qubit and extend its coherence to over a millisecond.

Color centers integrated with nanophotonic devices have emerged as a compelling platform for quantum science and technology. Here, we integrate tin-vacancy centers in a diamond waveguide and investigate the interaction with light at the single-photon level in both reflection and transmission. We observe single-emitter-induced extinction of the transmitted light up to 25% and measure the nonlinear effect on the photon statistics. Furthermore, we demonstrate fully tunable interference between the reflected single-photon field and laser light backscattered at the fiber end and show the corresponding controlled change between bunched and antibunched photon statistics in the reflected field.