  Electro-optical control of on-chip photonic devices is an essential tool for
efficient integrated photonics. Lithium niobate on insulator (LNOI) is an
emerging platform for on-chip photonics due to its large electro-optic
coefficient and high nonlinearity [1]. Integrating quantum emitters into LNOI
would extend their versatile use in classic photonics to quantum computing and
communication [2, 3]. Here, we incorporate single rare-earth ions (REI) quantum
emitters in electro-optical tunable lithium niobite (LN) thin films and
demonstrate control of LN microcavities coupled to REI over a frequency range
of 160 GHz with 5 \mus switching speed. Dynamical control of the cavities
enables the modulation of the Purcell enhancement of the REIs with short time
constants. Using the Purcell enhancement, we show evidence of detecting single
Yb3+ ions in LN cavities. Coupling quantum emitters in fast tunable photonic
devices is an efficient method to shape the waveform of the emitter [4]. It
also offers a platform to encode quantum information in the integration of a
spectral-temporal-spatial domain to achieve high levels of channel
multiplexing, as well as an approach to generate deterministic single-photon
sources [5, 6].
