Towards a scalable solid-state platform for spin qubits with a telecom optical interface

Scalable solid-state materials platforms with integrated spin qubits and silicon CMOS compatibility are highly desirable for quantum communication and computing applications. Platforms with qubits operating at telecom wavelengths are well suited for such optical quantum networks. Isolated atomic defects in crystals with a spin-photon interface are ideal quantum emitters and spin qubits; however, the brightest of these defect qubits often have transitions outside telecom wavelengths, limiting their direct use for long distance protocols. Meanwhile, defects with telecom optical transitions such as erbium have long radiative lifetimes and thus low photon emission rates. Current approaches addressing this challenge through Purcell enhancement present challenges in heterogeneous defect-device integration and processing complexities. Here we present a scalable approach towards high-quality CMOS-compatible telecom qubits enabled by rare-earth doped oxide films coupled to silicon photonic crystal cavities. The fabricated devices exhibit high quality factors and Purcell-enhanced optical lifetimes limited by the emitter homogeneous linewidths. This materials platform represents a significant step forward towards realizing quantum memories in a scalable qubit architecture compatible with mature silicon technologies.