In this work, we present a histogram post-processing method for Single Photon Avalanche Diode (SPAD)-based direct Time of Flight (d-ToF) depth measurement systems that compensates for the nonlinear behavior of the SPAD. The proposed compensation method approximates a linear behavior of the SPAD detector over time, resulting in a linearized histogram of timestamps even under strong background illumination conditions. The process can compensate for the distortion problem known as pile-up, which causes the corruption of the histogram of timestamps due to the variability of the intensity of the background and reflected laser light. The proposed approach has been first demonstrated with simulations, based on a physical model for the computation of the optical power budget and a numerical engine for the generation of the simulated train of timestamps. In particular, we consider a set of realistic parameters for typical SPAD-based d-ToF sensors, allowing us to validate the compensation method over a wider range of values. Finally, the method is validated with data from a real d-ToF sensor to demonstrate the effectiveness in mitigating the pile-up distortion phenomenon in the computation of the ToF.
The present paper shows possible ways to design monolithic Quantum Random Number Generators (QRNGs) in a standard CMOS technology. While all commercial QRNGs based on SPAD technology use an external light as main source of entropy, in the present implementation silicon-based photon sources are used. This approach allows the integration of monolithic QRNGs paving the way towards miniaturized and low-cost devices. Moreover, being the QRNG realized in a standard CMOS technology, in perspective, it can potentially be embedded in secure microprocessor. In the paper we show that the proposed approach is compact, produces a minimum event rate of about 1kHz, possibly extended in case of the implementation of multi-QRNGs working in parallel.
In this work we present a proof-of-concept of a photonic quantum random number generation scheme based on the entanglement between two internal degrees of freedom of single photons. The quantum correlations between momentum and polarization at the single photon level are verified by a Bell test in the CHSH form. The violation of this inequality not only ensures the entanglement, but also provides an estimation of the minimum entropy of the generated sequence. This allows to optimize the application of randomness extractor to obtain an unbiased sequence of random numbers.
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