Polarization-encoded quantum key distribution with a room-temperature telecom single-photon emitter

Area of Science:

• Quantum communication
• Solid-state physics
• Photonics

Background:

• Single-photon sources (SPSs) are crucial for quantum key distribution (QKD) but often require cryogenic cooling or frequency conversion.
• Existing QKD systems face limitations in practical deployment due to operational complexity and fiber transmission challenges.

Purpose of the Study:

• To demonstrate polarization-encoded QKD using a room-temperature SPS based on a gallium nitride (GaN) defect.
• To assess the performance of this novel SPS in real-world fiber optic conditions.

Main Methods:

• Utilized a gallium nitride (GaN) defect as a room-temperature single-photon source (SPS).
• Conducted field tests of polarization-encoded quantum key distribution (QKD) over deployed optical fibers of varying lengths and losses.
• Measured quantum bit error rate (QBER) and secure key rates.

Main Results:

• Achieved a secure key rate of 585.9 bps with a 5.0% QBER over 3.5 km of fiber (4.0 dB loss).
• Demonstrated a secure key rate of 50.4 bps with a 3.2% QBER over 32.5 km of fiber (11.2 dB loss).
• Observed improved performance with lower polarization mode dispersion in longer fiber spools.

Conclusions:

• Gallium nitride (GaN) defects show significant potential as room-temperature single-photon sources for practical quantum communication.
• The developed system offers a viable alternative to cryogenic or frequency-converted SPSs for QKD.
• Further research can optimize GaN defect SPSs for enhanced QKD performance and scalability.