High-Fidelity Ion State Detection Using Trap-Integrated Avalanche Photodiodes

Integrated technologies greatly enhance the prospects for practical quantum information processing and sensing devices based on trapped ions. High-speed and high-fidelity ion state readout is critical for any such application. Integrated detectors offer significant advantages for system portability and can also greatly facilitate parallel operations if a separate detector can be incorporated at each ion-trapping location. Here we demonstrate ion quantum state detection at room temperature utilizing single-photon avalanche diodes (SPADs) integrated directly into the substrate of silicon ion trapping chips. We detect the state of a trapped \(^{88}\text{Sr}^{+}\) ion via fluorescence collection with the SPAD, achieving \(99.92(1)\%\) average fidelity in 450 \(\mu\)s, opening the door to the application of integrated state detection to quantum computing and sensing utilizing arrays of trapped ions.