Basic entropy source

Light can be described as quantum particles – called photons.

Our Quantum Random Number Generator (QRNG) is utilizing fluctuations in the vacuum field |0> of light to generate a truly random seed. The vaccum state can be considered as the absense of a photon.

Traditionally, QRNGs based on measurements of the vacuum field use balanced homodyne detection. The vacuum state is mixed in a 50:50 beam splitter with light from a local oscillator and detected by two differentially coupled photo-diodes. However, this kind of optical homodyne detection is challenging to implement in a simple and cost-efficient manner.

Our approach simplifies the detection circuit by allowing for an arbitrary transmissivity η < 1 of the beam splitter and replacing one of the photodiodes by a beam dump. A compact implementatin of this scheme can be made by using the responsitivity of the photo-diode η as the beam splitter. In this way, the entropy source can be realized using a single VCSEL and a photo-diode.

Random number extraction

From the analogue output of the entropy source we extract a high speed sequence of random numbers using an Analogue to Digital Converter (ADC) and an Field Programmable Gate Array.

Traditional homodyne vacuum field detection
Alea’s simplified entropy source approach
Block diagram of QRNG module