Investigation of fractal noise in phase measurement of optical QRNG systems using digital and analog processing methods

Inhalt:
Quantum noise sources exhibit true randomness, ensuring secure random numbers than classical noise sources. Optical quantum random number generators (QRNGs) exploit a wide range of quantum phenomena, making them a suitable candidate for harnessing randomness. Among these, phase fluctuation based optical QRNGs are particularly popular owing to their straightforward approach. Conventional phase fluctuation QRNGs rely on translation of phase fluctuation to amplitude variation to produce randomness. Contemporary phase fluctuation QRNGs have also demonstrated simultaneous dual quadrature measurement methods, enabling phase measurements between quadrature components. In comparison to former conventional methods, phase measurement between quadratures intrinsically has improved quantum to classical noise properties. However, such phase measurements employ digital sampling prior to digital phase measurement which in turn gives rise to unintended deterministic fractal noise patterns in the probability distribution. Digital sampling due to its inherent amplitude quantization results in varying density of the measurable phase noise levels leading to deterministic fractal patterns. Alternatively, analog methods with analog building blocks act on the signal in the continuous domain. This paper primarily aims at analysing the occurrence of such deterministic fractal noise patterns due to digital sampling and in further explores analog methods to mitigate quantization induced adverse effects. To complement this study, the emergence of fractal noise patterns on phase measurements will be investigated with varying quantization levels. Additionally, SPICE simulations of the intended analog system will be performed using existing commercial models. The system's effectiveness will be evaluated, and its non-idealities will be compared against conventional methods.