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[ANGLÈS] Random numbers are extensively used in a broad range of applications. Nevertheless, there are two main markets from a commercial point of view: (i) secure communications and (ii) stochastic simulation. According to the generation rate and quality of the random numbers required, different approaches have been used so far, most of them based on pseudo-random number generation. However, these type of generators have already started showing weakness both in the quality and the generation rate. Thus, novel techniques based on physical processes are being studied and used nowadays. In this work an ultra-fast random number generator based on quantum vacuum fluctuations is demonstrated. Not only assuring the intrinsic randomness of quantum mechanics, but also being compliant with the speed needs of current applications. Employing a DFB laser diode in gain-switched mode and interferometry, the random phase generated in spontaneous emission events is translated into random amplitudes easily measurable using off-the-shelf components, i.e. measuring a quantum phenomena in a macroscopic way. Thus, using established models of semiconductor lasers, we predict a regime of high-visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These predictions are confirmed by measurement of pulse amplitude statistics at the exit of the interferometer.