Quantum light sources with configurable lifetime leveraging parity-time symmetry

Quantum light sources with configurable photon lifetimes are essential for large-scale quantum circuits, enabling applications in programmable quantum computing, various quantum key distribution protocols, and quantum tomography techniques. However, the fundamental trade-off between efficiency and photon lifetime imposes significant challenges on the design of high-performance large configurable lifetime quantum light sources. Here, we report on such chip-scale quantum light sources by harnessing the unique feature of parity-time (PT) symmetry. The core design centers on employing PT-symmetric coupling between two microresonators of distinct circumferences, enabling broad-range and selective tuning of intracavity photon density of states. By controlling the alignment between resonators, we achieved a 38-fold photon lifetime tuning range (4 ~ 158 ps), with the shortest lifetimes near the exceptional points of the PT-symmetric systems. The device generates energy-time entangled photon pairs with 87.1 ± 1.1% interference visibility and a heralded second-order autocorrelation of 𝑔 _ℎ ⁽²⁾ (0)= 35 0.069 ± 0.001. Our work highlights the potential of PT symmetry for advanced quantum applications, including high-speed communication and programmable quantum computing, quantum coherent tomography, and beyond.