Integrated photonics can bring million-atom quantum trap to chips

Researchers at the University of California Santa Barbara have made significant advances in miniaturizing cold atom quantum experiments, traditionally confined to large, delicate laboratory setups, onto palm-sized photonic chips. By leveraging integrated photonics—technology that manipulates light on silicon nitride chips—they developed a 3D magneto-optical trap capable of cooling and trapping over a million rubidium atoms to ultra-cold temperatures (around 250 microkelvin). This breakthrough enables highly precise quantum measurements previously only possible in bulky optical tables, opening the door to portable quantum sensors for applications such as earthquake detection, sea level rise monitoring, gravitational experiments, and dark matter searches. A key challenge addressed by the team was the noise and instability of commercial lasers, which hinder quantum precision. In 2024, they engineered an ultra-low linewidth, self-injection-locked 780 nm laser integrated directly on the chip, significantly reducing noise and enhancing measurement sensitivity. This integration of lasers, mirrors, modulators, and stabilizers onto