Free-Space Quantum Key Distribution

Abstract

Based on the firm laws of physics rather than unproven foundations of mathematical complexity, quantum cryptography provides a radically different solution for encryption and promises unconditional security. Quantum cryptography systems are typically built between two nodes connected to each other through fiber optic. This chapter focuses on quantum cryptography systems operating over free-space optical channels as a cost-effective and license-free alternative to fiber optic counterparts. It provides an overview of the different parts of an experimental free-space quantum communication link developed in the Spanish National Research Council (Madrid, Spain).Comment: 22 pages, 15 figure

The Evolution of Free-Space Quantum Key Distribution

“…One big challenge in free space QKD is that during daytime transmission the background noise is significantly higher and it can increase the dark count rate which results in a higher QBER and that lowers the key−rate. In an experiment at the Spanish National Research Council [18], researchers performed a 24 hour experiment and monitored how the background noise effects the QBER and thus the secret key−rate. The results show that there is a significant difference between the daylight and nighttime transmission.…”

Discrete phase CV-QKD over a hybrid free space - fiber channel with K-means clustering

“…7 For my research, we conducted a literature survey for a free space QKD. 8 The main challenge in establishing a long-distance CVQKD is to account for channel loss. Other CV-QKD deployments in the literature have demonstrated a frame error rate of 20% with a 100 MHz repetition rate and a loss of 6 dB in the channel.…”

Promising single-photon emitter in the blue-green spectral range with an epitaxial CdSe/ZnSe nanowire quantum dot

“…Only CdSe/ZnSe QDs have shown the possibility of room temperature single photon emissions in the visible spectral range [7]. Moreover, their emission spectral range at 520-600 nm is perfectly suited for QKD in free-space seawater and can also be used for free-space air QKD [8]. In this contribution we present a promising solid-state system able to emit triggered single-photons in the blue-green range up to room temperature.…”