Towards a Multi-Pixel Photon-to-Digital Converter for Time-Bin Quantum Key Distribution

Area of Science:

• Quantum Information Science
• Integrated Photonics
• Semiconductor Device Physics

Background:

• Quantum Key Distribution (QKD) systems require highly sensitive and precise single-photon detectors.
• Existing QKD receivers can be bulky and complex, limiting system miniaturization.
• Time-bin encoding is a robust method for QKD, but demands accurate temporal resolution.

Purpose of the Study:

• To design and demonstrate an integrated photon-to-digital converter (PDC) for time-bin encoded QKD.
• To develop a compact and efficient single-photon detection solution for QKD receivers.
• To improve the performance and robustness of QKD systems through advanced integrated electronics.

Main Methods:

• Integration of an 8x8 single-photon avalanche diode (SPAD) array with on-chip digital signal processing using TSMC 65 nm CMOS technology.
• Utilizing an array of time-to-digital converters (TDCs) for timestamping and processing photon detection events.
• Implementation of window gating for noise reduction and on-chip sorting of photon detections into time-bins.

Main Results:

• Achieved a timing resolution of 22.7 picoseconds (ps) Root Mean Square (RMS).
• Demonstrated successful operation in a time-bin setup with 158 ps time-bins.
• Operated at an optical wavelength of 410 nm, suitable for various QKD protocols.

Conclusions:

• The developed PDC is a key building block for next-generation QKD receivers.
• This integrated device enables the creation of compact, robust, and high-performance time-bin QKD systems.
• The PDC's capabilities pave the way for wider adoption and practical implementation of QKD technology.