Fully discrete 2.5-GHz balanced homodyne detector with 66-dB common-mode rejection ratio

Area of Science:

• Quantum Optics
• High-Frequency Electronics

Background:

• Balanced homodyne detectors (BHDs) are crucial for quantum information processing.
• Previous discrete BHD designs faced limitations in bandwidth and performance.

Purpose of the Study:

• To develop a high-performance, fully discrete balanced homodyne detector (BHD).
• To achieve a bandwidth exceeding 2 GHz with excellent gain flatness and common-mode rejection.

Main Methods:

• Utilized a Rogers 4350B PCB and a broadband RF choke bias network.
• Incorporated inter-stage π-section attenuators and precise photodiode matching.
• Implemented phase-magnitude compensation for signal integrity and noise suppression.

Main Results:

• Achieved a -3 dB bandwidth of 2.5 GHz and 1 dB gain flatness up to 2.4 GHz.
• Demonstrated a 16.5 dB signal-to-noise ratio at 2 GHz with excellent linearity.
• Attained a 66 dB common-mode rejection ratio at 2 GHz.

Conclusions:

• The developed discrete BHD represents state-of-the-art performance.
• This cost-effective and flexible detector is suitable for high-speed quantum key distribution and quantum random number generation.