Quantum Measurements Cannot be Proved to be Random

The postulates of quantum mechanics say that when a measurement is made on a quantum state the outcome of the measurement is random [1]. In classical physics, if the state of a closed system is known, then the state of that system is completely predictable. As far as we know, randomness only exists in quantum mechanics [2]. Everett proposed a purely unitary quantum theory [3] (without probability). However no known version of Everett’s purely unitary quantum theory can account for the appearance of probabilities without extra ad hoc postulates [4]. The probabilities in quantum mechanics are thought to be caused by randomness [1]. In this letter we show that, given a sufficiently large sequence of experimental data, there is no proof that the data is random [5]. Thus it is actually impossible to prove that randomness exists in quantum mechanics.