The method for generating a random bit sample involves a quantum tunneling barrier. The method generally has: generating a current of charges tunneling across said quantum tunneling barrier, the current of the tunneled charges having an instantaneous level varying randomly due to quantum tunneling fluctuations and forming a raw signal; from said raw signal, obtaining a raw bit sample having a first bit number n, the first bit number n being an integer; extracting the randomness out of the raw bit sample into the random bit sample, the random bit sample having a second bit number m being smaller than the first bit number n, said extracting being based on calibration data comprising at least a quantum contribution value of said quantum tunneling fluctuations in said raw bit sample; and on an external contribution value in said raw bit sample.