  Isolated solid-state atomic defects with telecom optical transitions are
ideal quantum photon emitters and spin qubits for applications in long-distance
quantum communication networks. Prototypical telecom defects such as erbium
suffer from poor photon emission rates, requiring photonic enhancement using
resonant optical cavities. Many of the traditional hosts for erbium ions are
not amenable to direct incorporation with existing integrated photonics
platforms, limiting scalable fabrication of qubit-based devices. Here we
present a scalable approach towards CMOS-compatible telecom qubits by using
erbium-doped titanium dioxide thin films grown atop silicon-on-insulator
substrates. From this heterostructure, we have fabricated one-dimensional
photonic crystal cavities demonstrating quality factors in excess of
$5\times10^{4}$ and corresponding Purcell-enhanced optical emission rates of
the erbium ensembles in excess of 200. This easily fabricated materials
platform represents an important step towards realizing telecom quantum
memories in a scalable qubit architecture compatible with mature silicon
technologies.
