  We propose a new approach to nondeterministic random number generation. In
theory, the randomness originated from the uncorrelated nature of consecutive
laser pulses with Poissonian photon number distribution and that of the
consecutive single photon detections is used to generate random bit. In
experiment, von Neumann correction method is applied to extract the final
random bit. This method is proved to be bias free in randomness generation,
provided that the single photon detections are mutually independent, and
further, it has the advantage in generation efficiency of random bits since no
postprocessing is needed. A true random number generator based on this new
method is realized and its randomness is guaranteed using three batteries of
statistical tests.
