Search

We present a new compact photonic quantum random number generator based on an emitter (source of entropy) and a single-photon detector integrated in the same silicon chip. Not only they are integrated one close to the other, but also they are fabricated with the same fabrication process. The emitter is a small silicon photomultiplier, composed of passively-quenched single photon avalanche diodes (SPADs), having the same layout of the single SPAD used as the detector. The emitter is a reverse-biased silicon p-n junction, generating photons mainly due to impact ionization during the avalanche breakdown process. The detector is shielded from ambient light by a top metal layer: only photons from the emitter are detected, making this integrated approach more robust. The random bits are extracted with a robust methodology based on the measurement of photon arrival times, using discrete time bins, in a time frame cyclically repeated in time. No postprocessing is required for the raw data to pass the statistical tests.

A robust quantum random number generation methodology has been developed and tested. The physical setup is based on a silicon nanocrystals light source coupled with a Si single photon avalanche diode driving a fully synchronous digital logic in a field-programmable gate array. After detailed analyses of the source and the detector, methods have been developed to make the nonidealities of the system and their consequent drawbacks decoupled from the quality of the generated random numbers. All the statistical tests in the national institute of standards and technology tests suite and the TestU01 Alphabit battery are consistently passed without a postprocessing operation on the raw data and without any feedback action on the photon source or any other parameter of the system. The maximum demonstrated bit-rate reaches 1.68 Mb/s, with an efficiency of 4 bits per detected photon. The modeling proves that the system is not influenced by variations of the internal and external parameters, such as the aging of the components and changing temperature.

A compact quantum random number generator based on the measurement of the arrival time of photons is presented in this paper. The new system consists of a silicon nanocrystals light emitting device coupled with a SPAD-based detector, integrated in a 3D chip packaging. The miniaturization of the device allows a remarkable reduction of the system size with respect the state of the art. The detector consists of an array of 16 pixels connected to a cluster of 4 reconfigurable TDCs with 12 bit resolution each for photon time stamping. Maximum system bit rate, limited by the emission efficiency of the source, is 0.4 Mbps.

A quantum random number generator (QRNG) based on a silicon nanocrystals (Si-NCs) light emitting device (LED) coupled with a silicon single photon avalanche photodiode (Si-SPAD) is presented. A simple setup is used for the generation of random bits. The modeled approach assures a negligible bias on datasets of ∼100 Mbits length. The raw data pass all the statistical tests in the National Institute of Standards and Technology (NIST) suite without any post-processing operations. The bit-rate of 0.6 Mbps is achieved. The information-theoretically provable randomness extractor of Toeplitz-hashing function is applied to longer datasets (∼1 Gbits) to extract the randomness, to minimize the bias, and consequently pass all the NIST tests. Stabilizing the temperature, resetting the applied current to the LED, or a feedback system can also be used as parameter control solutions to generate good quality, long datasets of random numbers suitable for cryptographic applications.

Silicon is the most common semiconductor in technology. Its main limit is the lacking of efficient light emission properties. Here quantum effects are exploited to fabricate optically active silicon photonics elements. The manuscript reports recent results obtained in different research fields spanning from bio- to integrated-photonics and nonlinear optics.

A small-sized photonic quantum random number generator, easy to be implemented in small electronic devices for secure data encryption and other applications, is highly demanding nowadays. Here, we propose a compact configuration with Silicon nanocrystals large area light emitting device (LED) coupled to a Silicon photomultiplier to generate random numbers. The random number generation methodology is based on the photon arrival time and is robust against the non-idealities of the detector and the source of quantum entropy. The raw data show high quality of randomness and pass all the statistical tests in national institute of standards and technology tests (NIST) suite without a post-processing algorithm. The highest bit rate is 0.5 Mbps with the efficiency of 4 bits per detected photon.

Silicon nanocrystals (Si-nc) are reviewed here for their interesting optical applications. On the one hand, they do exhibit quantum confinement effects. This allows turning silicon into a light-emitting material where luminescence can be excited by electrical injection. On the other hand, small sizes, large surfaces, and dielectric mismatch between the core and the surrounding matrix increase dramatically the nonlinear optical coefficients. This allows using Si-nc as a nonlinear material in different waveguide configurations. In this paper, we discuss specifically two different applications of Si-nc: (i) as a nonlinear material in various devices, e.g., in bistable optical cavities, in waveguide optical mode monitors that are based on two-photon excited luminescence detection, and in wavelength shifters by using four-wave mixing (FWM); (ii) as an entropy source for quantum random number generation, the key device for cryptography. (a) Top view optical image of a Si-nc-based whispering-gallery mode (WGM) microdisk resonator, vertically coupled with a bus waveguide. (b) Detail of the coupling zone. (c) Normalized waveguide transmission spectrum over a wide spectral range. The inset shows a blow up of a resonance with the radial and azimuthal mode orders and the Q factor value indicated.

A random number generation approach comprising a silicon nanocrystals LED (Si-NCs LED), silicon single photon avalanche photodiode (Si SPAD) and a field-programmable gate array (FPGA) is introduced. The Si-NCs LED is the source of entropy with photon emission in the visible range detectable by silicon detectors allowing the fabrication of an all-silicon-based device. The proposed quantum random number generator (QRNG) is robust against variations of the internal and external parameters such as aging of the components, changing temperature, the ambient interferences and the silicon detector artifacts. The raw data show high quality of randomness and passed all the statistical tests in National Institute of Standards and Technology (NIST) tests suite without the application of a post-processing algorithm. The efficiency of random number generation is 4-bits per detected photon.

We present a post-processing free quantum random number generator (QRNG) based on silicon nanocrystals (Si-NCs) LEDs as a source of randomness. The relatively simple setup for data extraction, a negligible bias measured from the datasets and applying no post-processing operations to the raw data are the main advantages of this QRNG . The obtained bit sequences pass all the NIST tests and the highest bit-rate achieved is 0.6 Mbps.

The increased control over nanoscale materials structuring is reshaping a number of applications and technologies at a fast pace. Semiconducting materials are playing an increasingly important role and Silicon is so far the most investigated one thanks to its broad availability and its fundamental role in microelectronics. Despite all its favorable properties, a major drawback of silicon is the lack of an efficient light emission mechanism that prevents its use in active photonics. Quantum size effects has been demonstrated a viable strategy to overcome this limit and to achieve light emission from silicon nanostructures. Si nanostructures are well controlled and can be tuned to achieve the desired properties, often exploiting the mature CMOS technological platform. Simultaneously several synthetic strategies have been developed in order to fabricate silicon quantum dots from chemical synthesis. Silicon chemistry is (rather) well known and permits to synthesize nanoparticles and to functionalize their surface using a broad number of reactions. Such flexibility allows for the grafting of both organic and inorganic species onto the Si QDs surface, to add functionalities and to protect the nanoparticle from their natural oxidations that, in turn, quenches the photoluminescence properties. Thus, despite the initial research was focused on the possibility to fabricate inorganic light sources that might rival with III-V or II-VI semiconductors. More recently a large research effort has been devoted to the use of Silicon nanostructures in biological-related applications. In such research topics Silicon has several properties take renders it an ideal candidate: it is considered a biocompatible material; it is readily dissolved in biological environment without releasing toxic byproducts; its red and tunable luminescence make it an interesting fluorescent tag able to exploit the tissue transparency window. During the presentation I will make a brief review of the fabrications methods proposed so far and I will discuss in details some of the recent research activities performed in our group in ICT- as well as in bio-related topics, all sharing the common denominator of Si QDs as active optical element. About the ICT-related topics I will discuss two applications of Si QDS. The first is about the use of Si QDs in quantum technologies. Data encryption and cryptography are core technologies hidden in our daily life and their importance is constantly growing. We have developed a robust physical random number generator that exploits Si QDs as a random bit source. The preliminary results are promising and the random sequences pass the standard NIST test suite. Furthermore the system is fully compatible with CMOS technology and can be scaled up to achieve large bit-rate generation. The second case in point is about the large optical nonlinearities possessed by Si QDs and their exploitation to develop integrated photonic devices. As a bio-related application I will discuss how nanostructured silicon microparticles can be used as fluorescent tags and are successfully up-taken by human dendritic cells without stimulating apoptosis up to a very large concentration. Porous silicon micro-particles (micro-pSi) with size in the range of 1-10 um are functionalized obtaining an interface that exposes either positive or negative charges at neutral pH. Their porous structure enables their use as drug carriers. Moreover, the surface modification stabilizes their intense photoluminescence and suggests their use for simultaneous imaging and drug delivery. The few cases discussed underline the great potentialities of Silicon nanostructures in different technologies and suggest its possible implementation as a functional interface between organic and inorganic systems.