Photonic integrated quantum key distribution receiver for multiple users.

Area of Science:

• Quantum communication technology
• Integrated photonics
• Quantum key distribution (QKD)

Background:

• Integrated photonics offers miniaturization, cost-effectiveness, and CMOS compatibility for quantum key distribution (QKD).
• Single-photon detectors (SPDs) remain the most expensive component in practical QKD systems, hindering widespread adoption.
• Multiplexing SPDs is crucial for reducing the overall cost and increasing the practicality of QKD systems.

Purpose of the Study:

• To design and fabricate a QKD receiver chip enabling multiple users to share a single set of SPDs.
• To demonstrate the feasibility of using time-division multiplexing on a photonic integrated chip for multi-user QKD.
• To reduce the cost barrier associated with SPDs in QKD systems.

Main Methods:

• Development of a novel QKD receiver chip utilizing integrated photonics.
• Implementation of a time-division multiplexing technique to share a single set of SPDs among multiple users.
• Fabrication and testing of a proof-of-principle chip-based QKD system.

Main Results:

• The chip successfully supports QKD for up to four users by multiplexing a single set of SPDs.
• The system achieved an average secret key rate of 13.68 kbps for four users.
• A low quantum bit error rate (QBER) of 0.51% was recorded over a simulated 20 km fiber distance.

Conclusions:

• The developed photonic integrated chip demonstrates the feasibility of multiplexing SPDs for multi-user QKD channels.
• This approach significantly reduces the cost of QKD systems by optimizing SPD utilization.
• The findings pave the way for the commercialization of quantum communication technology.