In general, any observed random process includes two qualitatively different forms of randomness: apparent randomness, which results both from ignorance or lack of control of degrees of freedom in the system, and intrinsic randomness, which is not ascribable to any such cause. While classical systems only possess the first kind of randomness, quantum systems may exhibit some intrinsic randomness. In this Letter, we provide quantum processes in which all the observed randomness is fully intrinsic. These results are derived under minimal assumptions: the validity of the no-signaling principle and an arbitrary (but not absolute) lack of freedom of choice. Our results prove that quantum predictions cannot be completed already in simple finite scenarios, for instance of three parties performing two dichotomic measurements. Moreover, the observed randomness tends to a perfect random bit when increasing the number of parties, thus, defining an explicit process attaining full randomness amplification.

• Received 8 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.100402