Near Infrared Devices and Protocols for Short Distance Quantum Key Distribution via Telecom Fibers

Quantum computers threaten current secure communication methods, prompting the emergence of new ideas to ensure communication resistant to this threat. Quantum Key Distribution (QKD) is one such technology leveraging quantum physics for secure symmetric key distribution. We, therefore, present an experimental setup with accompanying programs for initialization, calibration, and data processing designed for implementing QKD based on the BB84 protocol, using lasers at wavelengths of 810 nm. In our approach, Alice and Bob do not need to have synchronized watches nor share a synchronizing signal: their alignment in time is achieved by minimization of the bit error rate (BER). The protocol has been successfully executed at up to 8.3 dB loss, equivalent to 2.7 km of G.652.D telecom fiber, commonly used in current communications. Achieved BER is 1.0% at 0.7 dB loss and rises to 1.7% for 8.3 dB loss. While usual QKD solutions prefer expensive IR components and detectors in the telecom wavelength range, our study shows the viability of using affordable near-infrared (NIR) optics and silicon SPAD-based detectors for shorter distances.