Low-loss telecom-band nanofiber cavity for interfacing Yb atomic qubits

Seitaro Horikawa, Shinya Kato, Ryotaro Inoue, Takao Aoki, Akihisa Goban, Hideki Konishi

We demonstrate the fabrication of an optical nanofiber cavity designed for efficient interface with ytterbium (Yb) atoms at telecom-wavelength transitions. Replacing the conventional hydrogen-oxygen flame with a deuterium-oxygen flame in the heat-and-pull method suppresses hydroxyl-induced absorption losses and enables low-loss nanofiber production with minimal modifications to the existing fabrication system. Using this technique, we fabricate a nanofiber cavity at 1389 nm that exhibits an intrinsic round-trip loss of 0.31(2)% and a finesse of 2.0(1) x 10^3. This performance corresponds to a projected cooperativity of 90 when interfaced with Yb atoms, indicating that the cavity is well suited for efficient atom–photon coupling at telecom-wavelength transitions. Our results establish a practical route for developing fiber-integrated atom–photon interfaces in the telecom band, a critical step toward scalable quantum communication and distributed quantum computing.