Gain-switched vcsel as a quantum entropy source: the problem of quantum and classical noise

TL;DR

This paper investigates how classical and quantum noise affect the extraction of true quantum randomness from a gain-switched VCSEL used as a quantum entropy source, emphasizing the importance of noise evaluation for secure random number generation.

Contribution

It introduces a method to evaluate classical noise contribution and calculates the quantum reduction factor necessary for post-processing in VCSEL-based quantum random number generators.

Findings

Classical noise significantly impacts polarization-based quantum randomness extraction.

A procedure to quantify quantum reduction factor for secure post-processing.

Insights into optimizing VCSEL operation for quantum entropy sources.

Abstract

We consider the problem of quantum noise extraction from polarization swapping in a gain-switched VCSEL. The principle of operation of a quantum random number generator is based on the generation of laser pulses with one of two orthogonal polarization states, followed by digitization of polarization-resolved pulses with a comparator. At intensity values of laser pulses close to the threshold value of the comparator, the contribution of the classical noise of the photodetector will have a crucial role in making a decision on the choice of a logical zero or one. We show how to evaluate the contribution of classical noise and how to calculate the quantum reduction factor required for post-processing.