True randomness from realistic quantum devices

TL;DR

This paper presents a framework for analyzing realistic quantum random number generators (QRNGs) to ensure their output achieves true randomness despite noise and imperfections.

Contribution

It introduces a method to evaluate and determine the necessary post-processing for QRNGs to produce genuinely unpredictable randomness.

Findings

Framework for analyzing QRNG noise effects

Guidelines for post-processing to ensure true randomness

Applicable to practical quantum devices

Abstract

Even if the output of a Random Number Generator (RNG) is perfectly uniformly distributed, it may be correlated to pre-existing information and therefore be predictable. Statistical tests are thus not sufficient to guarantee that an RNG is usable for applications, e.g., in cryptography or gambling, where unpredictability is important. To enable such applications a stronger notion of randomness, termed "true randomness", is required, which includes independence from prior information. Quantum systems are particularly suitable for true randomness generation, as their unpredictability can be proved based on physical principles. Practical implementations of Quantum RNGs (QRNGs) are however always subject to noise, i.e., influences which are not fully controlled. This reduces the quality of the raw randomness generated by the device, making it necessary to post-process it. Here we provide a framework to analyse realistic QRNGs and to determine the post-processing that is necessary to turn their raw output into true randomness.