Ultrafast Telecom Single Photons from Colloidal Quantum Dots

Quantum science has transitioned from laboratory experiments to real-world applications, such as secure long-distance communication and enhanced computational speed. The telecom industry has evolved to meet the increasing need for faster data transmission, particularly within the low-loss C-band (1530-1565 nm). Significant progress has been made in single-photon generation within the telecom O-band (1260-1360 nm) at both low and room temperatures across various material platforms. However, existing telecom sources are still limited by long radiative lifetimes, material instability, and the need for cryogenic conditions.<br/>Our research addresses these challenges by using stable colloidal PbS/CdS quantum dots emitting at 1550 nm (C-band) or 1350 nm (O-band), embedded in a solution-synthesized nanoparticle-on-mirror cavity. These quantum dots experience extreme Purcell factors of several thousands, resulting in ultrafast emission lifetimes on the picosecond scale. The single-photon action of the nanocavity-coupled quantum dots is confirmed pulsed second-order autocorrelation measurements.<br/>Future improvements in quantum dot synthesis, aimed at minimizing intrinsic linewidth and enhancing coherence, similar to advances seen in colloidal lead halide perovskite quantum dots, could further reduce bandwidth to its lifetime limit, paving the way for ideal on-demand and indistinguishable single-photon generation.