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, quantum communications, and quantum metrology. 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 a broad range and selective tuning of the intracavity photon density of states. By controlling the alignment between resonators, we achieved a near 20-fold photon lifetime tuning range (7.1 ± 1.5 ~ 129.6 ± 1.9 ps), with the shortest lifetimes near the exceptional point (EP). The device generates energy-time entangled photon pairs with 87.1 ± 1.1% interference visibility and a heralded second-order autocorrelation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mi>g</mml:mi></mml:mrow> <mml:mrow><mml:mi>H</mml:mi></mml:mrow> <mml:mrow> <mml:mfenced><mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:mfenced> </mml:mrow> </mml:msubsup> <mml:mfenced><mml:mrow><mml:mn>0</mml:mn></mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo></mml:math> 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.