Method and system for quantum key distribution

Abstract The present disclosure refers to a method for quantum key distribution, the method being implementable in a system which comprises: a transmission line (1o) for transmitting optical 5 signals between a first data processing device (11) and a second data processing device (12) and an optical amplifier (14) disposed at the transmission line (1o), the optical amplifier (14) comprising an active fiber section (15) and a pumping device (16), the method comprising: determining a ratio between a target maximum gain and a target operating gain of the optical amplifier (14); determining an active fiber section length such that the optical signals with a o target maximum signal power are amplified with at most the target maximum gain; determining an operating pumping power of the pumping device (16) below the maximum pumping power such that the optical signals are amplified with a target operating gain according to the determined ratio between the target maximum gain and the target operating gain; and determining a shared key between the first data processing device (1o) and the sec 5 ond data processing device (11) by quantum key distribution comprising amplifying the optical signals via the optical amplifier (14) by operating the pumping device (16) at the operating pumping power. (Fig.1) C_) -El