Środowiskowe Seminarium z Informacji i Technologii Kwantowych

The Seminar will take a HYBRID form. It will take place in room 1.03 but will be simmultaneously tranmitted via ZOOM under the following link: https://zoom.us/j/92894130767 (Passcode: R6Vx6E)

While the ambition of QKD technology is to make the cryptographic key distribution secure even against the most sophisticated physical attacks permitted by quantum theory, it falls short of delivering high key rates when the distance between Alice and Bob is large enough that one has to use either satellite communication or a series of quantum repeaters. Hence, it is interesting to consider alternative key distribution protocols which are still secure against restricted class of attacks such as passive eavesdropping where an unauthorized third party collects passively a fraction of the signal that escapes detection by the legitimate recipient. Here we introduce and analyze theoretically the performance of the optical key distribution (OKD) relying on intensity modulation/direct detection of the optical carrier, where the security is ensured by the presence of the shot noise that inevitably accompanies eavesdropper’s attempt to detect the collected signal. We show that the key rate depends on a ratio that compares legitimate recipient’s and eavesdropper’s capabilities to detect the signal, including noise contributed by their respective detectors. Finally we present a realistic numerical example to estimate an attainable key length distributed during a single low-earth-orbit satellite pass which significantly exceeds key lengths attained in satellite QKD missions realized until now.