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.
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.
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.
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
Certifying random number generators is challenging, especially in security-critical fields like cryptography. Here, we demonstrate a measurement-device-independent quantum random number generator (MDI-QRNG) using high-dimensional photonic path states. Our setup extends the standard qubit beam-splitter QRNG to a three-output version with tunable fiber-optic interferometers acting as tunable beam splitters and superconducting detectors. This setup generates over 1.2 bits per round and 1.77 Mbits per second of certifiably secure private randomness without requiring \emph{any} trust in the measurement apparatus, a critical requirement for the security of real-world cryptographic applications. Our results demonstrate certifiably secure high-dimensional quantum random-number generation, paving the way for practical, scalable QRNGs without the need for complex devices.
Quantum mechanics provides the means of generating genuine randomness that is impossible with deterministic classical processes. Remarkably, the unpredictability of randomness can be certified in a manner that is independent of implementation devices. Here, we present an experimental study of device-independent quantum random number generation based on a detection-loophole-free Bell test with entangled photons. In the randomness analysis, without the independent identical distribution assumption, we consider the worst case scenario that the adversary launches the most powerful attacks against the quantum adversary. After considering statistical fluctuations and applying an 80 Gb×45.6 Mb Toeplitz matrix hashing, we achieve a final random bit rate of 114 bits/s, with a failure probability less than 10^{-5}. This marks a critical step towards realistic applications in cryptography and fundamental physics tests.
Quantum key distribution (QKD) using entangled photon sources (EPS) is a cornerstone of secure communication. Despite rapid advances in QKD, conventional protocols still employ beam splitters (BSs) for passive random basis selection. However, BSs intrinsically suffer from photon loss, imperfect splitting ratios, and polarization dependence, limiting the key rate, increasing the quantum bit error rate (QBER), and constraining scalability, particularly over long distances. By contrast, EPSs based on spontaneous parametric down-conversion (SPDC) intrinsically exhibit quantum randomness in spatial and spectral degrees of freedom, offering a natural replacement for BS-based basis selection. Here, we demonstrate a proof-of-concept QKD scheme that exploits the intrinsic spatial randomness of SPDC without employing beam splitters. The annular SPDC emission ring is divided into four spatial sections, effectively generating two independent EPSs whose photon pairs are distributed to Alice and Bob. Crucially, the measurement basis is not predetermined but is assigned after photon detection by exploiting intrinsic detector timing jitter, thereby concealing the basis information from a potential eavesdropper. This post-detection basis assignment emulates stochastic basis choice while avoiding BS-induced losses and bias. Experimentally, our scheme achieves a 6.4-fold enhancement in sifted key rate, a consistently reduced QBER, and a near-ideal encoding balance between linear and rectilinear bases. Furthermore, the need for four spatial channels can be avoided by employing wavelength demultiplexing to generate two EPSs at distinct wavelength pairs. Harnessing intrinsic spatial/spectral randomness thus enables robust, bias-free, high-rate, and low-QBER QKD, offering a scalable pathway for next-generation quantum networks.
Quantum random number generators (QRNGs) can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics, which play important roles in many applications. However, the true randomness acquisition could be subjected to attacks from untrusted devices involved or their deviations from the theoretical modeling in real-life implementation. We propose and experimentally demonstrate a source-device-independent QRNG, which enables one to access true random bits with an untrusted source device. The random bits are generated by measuring the arrival time of either photon of the time–energy entangled photon pairs produced from spontaneous parametric downconversion, where the entanglement is testified through the observation of nonlocal dispersion cancellation. In experiment, we extract a generation rate of 4 Mbps by a modified entropic uncertainty relation, which can be improved to gigabits per second by using advanced single-photon detectors. Our approach provides a promising candidate for QRNGs with no characterization or error-prone source devices in practice.