we presents a 32 × 1 linear Single Photon Avalanche Diode array for quantum communication applications. The array provides the position of the single photon detected, and can identify multiple photon coincidences.
Quantum communication is a fast-growing field that takes advantage of the quantum physics laws to protect and secure sensitive data. This work takes part of the European project UNIQORN (Affordable Quantum Communication for Everyone: Revolutionizing the Ecosystem from Fabrication to Application) whose aim is to develop a Quantum System on Chip (QSoC) for telecom application. The Integrated Circuit (IC) designed contributes in the QRNG block of the system, tailored to communicate with the integrated non-linear optics circuit. Such detector is a 32×1 linear array based on Single-Photon Avalanche-Diode (SPAD) detectors for the generation of a raw random number, by revealing the position on the array of the single photon impinging on it, realized in a BCD 0.16 μm technology. The linear array architecture consists of 32 pixels, pitched at 125 μm, each made by 4 SPADs with different diameter (5 μm, 10 μm, 20 μm, 50 μm). Two operation modes are implemented: Single-Hit Mode, needed to reveal the (5-bit) position of the pixel triggered by a single photon, representing a random number, in a time window synchronous with the laser emission. Multi Hit Mode, used to identify a coincidence of a certain number of photons(more than one, two, three or four) detected within a specified time window, thanks to a multi threshold coincidence detection logic.
Quantum random number generators (QRNGs) can generate true random numbers and have significant applications in quantum communication, numerical computation, and model simulation. However, the rate of random number generation based on photon detection is constrained by the maximum count rate of a single-photon detector. Therefore, improving the efficiency of random number generation for individual photon detection events becomes an optional way to increase the rate of random number generation. In this paper, multidimensional photon detection is implemented to enhance single-photon detection events, thereby providing a new, to the best of our knowledge, technical development strategy for high-speed random number generators. The temporal and spatial coherence of coherent-state photons is utilized as a valuable quantum resource, enabling us to achieve the simultaneous extraction of time-space measurement collapsed randomness for single-photon detection events using a chip-scale CMOS-integrated single-photon avalanche diode array. The efficiency of random number generation for single-photon detection events is effectively improved. In our experiments, up to 20 bits can be extracted from an individual photon detection event, and the rate of random number generation reaches up to 2.067 Gbps.
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 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.
During this thesis work, two approaches to single-photon detection at telecom wavelengths have been investigated. The first one focuses on improving the performance of commercially available semiconductor single photon avalanche diodes (SPADs) to meet quantum communication requirements, and the second one describes the development and characterization of large active-area superconducting nanowire single-photon detectors (SNSPDs). On the application side, quantum random number generation (QRNG) was implemented using two schemes based on two different types of single photon detectors activated by a LED.