Efficient fibre-pigtailed source of indistinguishable single photons.

Semiconductor quantum dots in microcavities are an excellent platform for the efficient generation of indistinguishable single photons. However, their use in a wide range of quantum technologies requires their controlled fabrication and integration in compact closed-cycle cryocoolers, with a key challenge being the efficient and stable extraction of the single photons into a single-mode fibre. Here we report on a method for the fibre-pigtailing of deterministically fabricated single-photon sources. Our technique allows for nanometre-scale alignment accuracy between the source and a fibre, alignment that persists all the way from room temperature to 2.4 K. We demonstrate high performance of the device under near-resonant optical excitation with a photon indistinguishability of 97.5 % and a brightness at the output fibre of the system of 20.8 %. We show that the indistinguishability and single-photon rate are stable for over ten hours of continuous operation in a single cooldown. We further confirm that the device performance is not degraded by nine successive cooldown-warmup cycles.