A compact quantum random number generator (QRNG) based on an array of Single Photon Avalanche Diodes (SPADs) is presented here. The main feature of the proposed chip is the capability to generate random numbers without the use of any external source of light. In this view, SPADs are configured to be used in two ways: 1) as a controlled light emitter and 2) as a detector. An embedded logic is able to distinguish dark events against detected emitted photon in such a way to make the system sensitive only to the presence of light. The extracted random bits show a uniform distribution and the QRNG, thanks to an integrated conditioning block maximizing the output entropy, eventually passes all AIS31 tests. The average raw bit rate in the default device configuration (one enabled column) is measured equal to 800 kbps.
A compact quantum random number generator (QRNG) based on an array of Single Photon Avalanche Diodes (SPADs) is presented here. The main feature of the proposed chip is the capability to generate random numbers without the use of any external source of light. In this view, SPADs are configured to be used in two ways: 1) as a controlled light emitter and 2) as a detector. An embedded logic is able to distinguish dark events against detected emitted photon in such a way to make the system sensitive only to the presence of light. The extracted random bits show a uniform distribution and the QRNG, thanks to an integrated conditioning block maximizing the output entropy, eventually passes all AIS31 tests. The average raw bit rate in the default device configuration (one enabled column) is measured equal to 800 kbps.
A compact quantum random number generator based on an array of Single Photon Avalanche Diode (SP AD) is presented here. As the main feature, the proposed chip has the capability to generate random numbers without the use of an external source of light. In the present approach, SP AD devices are used as emitters and as detectors. An embedded logic allows distinguishing dark events from events coming from the photon emission. The extracted random bit sequence shows a quite uniform distribution and after being post-processed by means of an integrated circuit, used to maximize the entropy of the system, is able to pass the AIS31 test. The average bit rate is 400 kbps.
For globally connected devices like smart phones, personal computers and Internet-of-things devices, the ability to generate random numbers is essential for execution of cryptographic protocols responsible for information security. Generally, a random number generator should be small, robust, utilize as few hardware and energy resources as possible, yet provide excellent randomness at a high enough speed (bitrate) for a given purpose. In this work we present a quantum random number generator (QRNG) which makes use of a photoelectric effect in single-photon avalanche diodes (SPADs) as a source of randomness and is scalable to any desired bitrate. We use the random flip-flop method in which random bits are obtained by periodic sampling of a randomly toggling flip-flop. For the first time we investigate this method in detail and find that, out of two main imperfections, bias is due only to hardware imperfections while autocorrelation predominantly resides with the method itself. SPADs are integrated on a silicon chip together with passive quenching and digital pulse-shaping circuitry, using a standard 180 nm CMOS process. A separate FPGA chip derives random numbers from the detection signals. The basic QRNG cell, made of only two SPADs and a few logic circuits, can generate up to 20 Mbit/s that pass NIST statistical tests without any further postprocessing. This technology allows integration of a QRNG on a single silicon chip using readily available industrial processes.
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.
Single-Photon Avalanche Diodes (SPADs) are solid-state photo-detectors capable of detecting single photons by exploiting the avalanche effect that occurs in the breakdown of a p-n junction biased above breakdown voltage. By this effect, a SPAD translates an incoming photon to a macroscopic current pulse. These devices are currently used for building medical devices characterized by a very high time resolution. An appealing application of SPAD is to use them as a basic block for building the entropy source of true random number generators. In this paper we focus on such application, and we explore the design challenges behind the realization of a quantum random number generator based on a massively parallel array of SPADs. The matrix under investigation comprises 512×128 independent cells that convert photons onto a raw bit-stream, which, as ensured by the properties of quantum physics, is characterized by a very high level of randomness. The sequences are read out in a 128-bit parallel bus, concatenated, and pipelined onto a de-biasing filter. Subsequently, we fabricated the proposed chip using a standard CMOS process. Our results, achieved on the manufactured device and coupling two matrices, show that our architecture can reach up to 5 Gbit/s while consuming 25pJ/bit, thus demonstrating scalability and performance for any random number generators based on SPADs.
A robust true random number generator (TRNG), able to assure high quality output at different working conditions, is an attractive solution in secure communication application, because it increases resilience against possible external attacks. Among different TRNGs, quantum RNGs (QRNG) represent a good candidate for such systems, because of their compactness, low cost and performance [1–6]. They typically consist of a source of photons, such as an attenuated LED, coupled to a detector with single photon capability (SPAD). Many works in the literature have used a single detector [1–4] for random bit extraction. These devices are characterized by a limited bit rate [1], which can be increased by exploiting the arrival time of photons at the cost of circuit and system complexity [2–4]. Recent works [5–6] proposed to implement an array of detectors based on SPAD working in parallel thus extending the speed of QRNG up to 5 Gb/s [5]. Despite the high bit rate, the main drawback of [5] is the strong dependence of each pixel bias on the impinging light intensity which forces the system to work only for a narrow range of photon flux that poses several constraints on the design of the final QRNG system, e.g. the need of a feedback control loop to maintain a constant flux of photons, and of a uniform distribution of light over the entire sensor. Moreover, it is impractical to implement algorithms for bit extraction to all detectors of the array because of different responses and mismatches among SPADs.
This work describes a monolithically integrated photonic quantum random number generator (QRNG) in0.35μmCMOS. This QRNG consists of a light-emitting diode inside a deep N-well, a ring single-photon avalanche diode (SPAD), a fast cascoded active quenching and resetting circuit, and an analog evaluation circuit determining whether the random bit is a “0” or “1”. The random bits are created by comparison of two consecutive time intervals between photon detections using charging and discharging a capacitor with a constant current as well as a comparator. The time intervals can be in the range from 10 ns to10μs. With±3.3Vsupply voltage, the power consumption of the complete circuits is between 1.1 mW and 4.55 mW depending on the LED emission and detection rate of the SPAD. After XOR-hashing, the NIST tests were passed.