We introduce a randomness beacon that the public can verify. It is based on a heralded spontaneous parametric down-conversion (SPDC) single-photon quantum random number generator (QRNG) along with a 50:50 non-polarizing beamsplitter. We time-tagged detection events from two spatial modes and processed them using a von Neumann debiasing step and SHA-256 entropy extraction. The resulting binary stream meets all NIST SP 800-22 statistical tests, demonstrating its strong randomness. We used epoch-based segmentation and a forward hash-chain to create a clear and repeatable beacon log. This lets users verify information using open-source cryptographic tools and online platforms.
We introduce a randomness beacon that the public can verify. It is based on a heralded spontaneous parametric down-conversion (SPDC) single-photon quantum random number generator (QRNG) along with a 50:50 non-polarizing beamsplitter. We time-tagged detection events from two spatial modes and processed them using a von Neumann debiasing step and SHA-256 entropy extraction. The resulting binary stream meets all NIST SP 800-22 statistical tests, demonstrating its strong randomness. We used epoch-based segmentation and a forward hash-chain to create a clear and repeatable beacon log. This lets users verify information using open-source cryptographic tools and online platforms.
Spontaneous parametric down-conversion (SPDC), an inherently random quantum process, produces pair photons with strong temporal and spatial correlations due to energy and momentum conservation, and acts as the key for quantum random number generation (QRNG). Standard QRNG methods primarily use temporal correlations with beam splitters, limiting bit rates. However, due to spatial correlation, the pair photons in non-collinear phase-matched SPDC-setup appear at diametrically opposite points on an annular spatial distribution. Therefore, exploring the temporal correlation between the spatially correlated photon-pairs from different sections of the annual ring can directly lead to device-independent, multi-bit QRNG at a high rate, eliminating the need of a physical object such as a beam splitter. As a proof-of-concept, we report on high-bit-rate QRNG by using spatial correlation of photon-pairs by sectioning the SPDC ring of a non-collinear, degenerate, high-brightness source and temporal correlation between the diametrically opposite sections. Dividing the annular ring of the high-brightness photon-pair source based on a 20-mm-long, type-0 phase-matched, periodically poled KTP crystal into four sections, recording the timestamp of the coincidences (window of 1 ns) between photons from diametrically opposite sections and assigning bits (0 and 1), we extracted 90 × 106 raw bits over 27.7 s at a pump power of 17 mW. Using minimum entropy evaluation, we determined an extraction ratio of over 95 % for raw bits. Further, using Toeplitz matrix-based post-processing, we developed QRNG with bit rate of 3 Mbps, passing all NIST 800-22 and TestU01 test suites. The generic scheme shows the possibility of further enhancement of bit rate with more sectioning of the SPDC ring.
Device-independent quantum random number generators (DI-QRNGs) are crucial for many information-processing applications, requiring certified quantumness to ensure genuine randomness. However, inherent technical challenges in implementing quantumness tests often result in a low bit rate. Here, we present a high-bit-rate DI-QRNG with live quantumness certification through the Bell test. By employing spontaneous parametric down-conversion (SPDC) in a polarization Sagnac interferometer, which generates entangled degenerate pair-photons in annular ring distribution with strong temporal and spatial correlations due to energy and momentum conservation, we divide the annular ring into six diametrically opposite sections, forming three robust entangled photon sources from a single laser and nonlinear crystal. The pair-photons from these three sources exhibit bias-free quantum mechanical randomness. By utilizing the coincidence counts of pair-photons from two sources, we generate raw bits, while the third source simultaneously measures the Bell’s parameter without any loss of QRNG bits. We have generated 90 million raw bits in 46.4 seconds with the Bell parameter (S > 2), with a minimum entropy extraction ratio exceeding 97%. Post-processed using a Toeplitz matrix, the DI-QRNG achieves a bit rate of 1.8 Mbps, passing all NIST 800-22 and TestU01 tests. In the absence of Bell’s parameter for a non-maximally entangled state, g (2) (0) can be the metric for quantumness measure. Free from the requirement of any physical devices such as beam-splitters, this scalable DI-QRNG scheme promises high bit-rates and trustworthy certifications essential for practical applications.
Abstract This work proposes a quantum true random number generator (QTRNG) architecture based on spontaneous parametric down-conversion (SPDC) photon sources, single-photon avalanche diodes (SPADs), and Schmidt-mode-resolved joint spectral intensity (JSI) filtering. The system employs a numerically optimized spectral filter to isolate the dominant Schmidt mode, effectively suppressing spectral entanglement and enhancing source-level purity. Simulation results confirm that the optimized configuration achieves a Schmidt number of 1.0008, spectral purity of 0.9992, and entanglement entropy of 0.0052 bits. The bitstream generated from coincidence detections demonstrates ideal statistical properties, including a min-entropy per bit of H∞=0.9997 and a total of 17.85 million extractable bits, without requiring post-processing. The randomness output passes all tests in the NIST SP 800-22 and Dieharder suites with a 100% success rate, confirming its unpredictability and cryptographic suitability. The system is also computationally efficient, with a runtime of 320 seconds and memory usage of 12.83~MB for 109 pulses, making it suitable for real-time embedded applications. This study establishes a scalable and physically secure QTRNG framework grounded in spectral mode engineering and finite-size security certification.
Quantum random number generators (QRNGs) play a crucial role in cryptography, secure communications, and stochastic simulations. This study presents the metrological characterization of a QRNG implemented on the Quandela photonic quantum computer, available via the cloud. The system generates random sequences using single photons and beam splitters, where quantum superposition ensures a fundamentally probabilistic outcome. A key aspect of this characterization involves defining the sample size and the number of qubits used. The Quandela quantum processor operates with up to six qubits, corresponding to six photons in twelve optical modes. However, the simultaneous use of multiple photons can introduce unintended correlations due to quantum interference, affecting the quality of randomness. To ensure independent bit generation, experiments were conducted with a single photon per measurement, producing one-bit outcomes per detection event. The analysis focuses on repeatability and reproducibility, examining the statistical properties of the generated sequences. Raw sequences underwent randomness testing using NIST SP800-22 and entropy assessment with NIST SP800-90B. Initial results indicate that raw sequences exhibit biases due to imperfections in single-photon sources and optical elements. The sequences generated by the Quandela photonic quantum processor failed most NIST SP800-22 tests, including Frequency (Global and Block), Runs, and Approximate Entropy, with six tests showing a 100% failure rate. Additionally, under the NIST SP800-90B evaluation, 100% of the raw sequences failed the independence and identically distributed (IID) test, highlighting strong correlations and statistical dependencies. To enhance randomness quality, post-processing techniques were applied, including Von Neumann and the combination Samuelson + Von Neumann extractors. These methods significantly improved bit balance and reduced statistical dependencies. After post-processing, all sequences passed the NIST SP800-90B IID test, and the entropy per bit increased to 0.771 ± 0.005 for the Ascella processor, ensuring improved randomness quality. The findings highlight the metrological challenges in QRNGs based on photonic quantum processors, emphasizing the need for rigorous statistical validation. Despite system-specific noise, the quantum origin of randomness remains preserved, ensuring that the extracted sequences retain their fundamental unpredictability. Additionally, limitations associated with photonic quantum systems, such as hardware imperfections, photon losses, and optical misalignment, are discussed in the context of their impact on randomness quality. Despite these limitations, rigorous statistical validation and post-processing enable the generation of high-quality random sequences suitable for cryptographic protocols, secure key distribution, and high-performance computing This study reinforces the importance of metrology in quantum technologies, providing a structured methodology for optimizing QRNG reliability and performance.
What is the most efficient way to generate random numbers deviceindependently using a photon pair source based on spontaneous parametric down conversion (SPDC)? We consider this question by comparing two implementations of a detection-loophole-free Bell test. In particular, we study in detail a scenario where a heralded single photon source (HSPS) is used to herald path-entangled states, i.e. entanglement between two spatial modes sharing a single photon and where nonlocality is revealed using photon counting preceded by small displacement operations. ar X iv :1 40 9. 80 51 v1 [ qu an tph ] 2 9 Se p 20 14 Device-independent quantum random number generator with a photon pair source 2 We start by giving a theoretical description of such a measurement. We then show how to optimize the Bell-CHSH violation through a non-perturbative calculation, taking the main experimental imperfections into account. We finally bound the amount of randomness that can be extracted and compare it to the one obtained with the conventional scenario using photon pairs entangled e.g. in polarization and analyzed through photon counting. While the former requires higher overall detection efficiencies, it is far more efficient in terms of both the entropy per experimental run and the rate of random bit generation. PACS numbers: 03.65.Ud Device-independent quantum random number generator with a photon pair source 3
Quantum random number generators (QRNG) are the prime source of randomness, by exploiting the unpredictable nature of Quantum mechanics QRNG aims to provide a string of completely random utterly unpredictable numbers. QRNGs are crucial for cryptography, scientific calculation, simulation, and many more real-world applications. Our Optical Quantum Random Number Generator (OQRNG) utilizes a high-speed pulsating laser, a Polarizing beam splitter (PBS), photodetectors, and advanced signal processing units that capture and digitize random photon intensity forming the raw random bit stream. This technique is famously known as Branching Path Technique. After that, we implement rigorous testing that encompasses the statistical randomness tests developed by National Institute of Standards and Technology (NIST) to ensure the guaranteed ran-domness meets security standards. A user-friendly Graphic user interface (GUI) simplifies interaction with the QRNG allowing the user to configure device settings, monitor system performance, and securely extract random numbers. Our findings help us demonstrate the superiority of QRNGs over classical random number generators, and highlight the potential of photon-based QRNGs and their environmentally friendly and efficient random number generation.