GHz QKD at telecom wavelengths using up-conversion detectors

TL;DR

This paper presents a novel hybrid detection scheme for telecom wavelength QKD using nonlinear up-conversion and silicon SPADs, achieving high raw count rates and low error rates over 25 km.

Contribution

The work introduces a high-efficiency wavelength conversion method combined with low-jitter silicon SPADs for improved telecom wavelength QKD performance.

Findings

Achieved MHz raw count rates in QKD over 25 km

Demonstrated QBER below 2%

Estimated secure key rates over 100 kbit/s

Abstract

We have developed a hybrid single photon detection scheme for telecom wavelengths based on nonlinear sum-frequency generation and silicon single-photon avalanche diodes (SPADs). The SPAD devices employed have been designed to have very narrow temporal response, i.e. low jitter, which we can exploit for increasing the allowable bit rate for quantum key distribution. The wavelength conversion is obtained using periodically poled Lithium niobate waveguides (W/Gs). The inherently high efficiency of these W/Gs allows us to use a continuous wave laser to seed the nonlinear conversion so as to have a continuous detection scheme. We also present a 1.27GHz qubit repetition rate, one-way phase encoding, quantum key distribution experiment operating at telecom wavelengths that takes advantage of this detection scheme. The proof of principle experiment shows a system capable of MHz raw count rates with a QBER less than 2% and estimated secure key rates greater than 100 kbit/s over 25 km.