Quantum Random Generator Research Articles

Analysis of the effects of imperfections in an optical heterodyne quantum random-number generator

Quantum random numbers generators (QRNGs) rely on quantum systems to produce sequences of random numbers with an overall lower level of predictability than classical algorithmic systems. Over the past two decades, phase randomizations of coherent sources from quantum spontaneous emission effects have gained a lot of interest due to their operational simplicity, cost-contained components, and ability to generate random numbers at high rates. However, many QRNGs require optimal calibration and alignment to ensure efficient and effective random-number generation. This work demonstrates a detailed analysis of a heterodyne measurement based QRNG, which implements phase randomization from two independent laser sources. The analysis also quantifies the effects of setup misalignments using the Kullback-Leibler divergence as a benchmark to assess the limiting conditions of secure random-number generation.

A SPAD-based random number generator pixel based on the arrival time of photons

A quantum random generator based on photon detection is here presented. The system consists of a photon source, typically a commercial LED, coupled with a detector with single photon detection capability. The detector is composed of a Single-Photon Avalanche Diode (SPAD) and a time stamp circuit, which samples the arrival time of impinging photons within a predefined temporal window. The proposed implementation optimizes the area, allowing embedding all circuitry into a single pixel, and increases the efficiency of random bit extraction. Moreover, the adopted fast pre-charge mode of the SPAD quenching circuit reduces the afterpulsing probability, and hence possible undesirable correlation in the resulting random bit sequence. Thanks to the implemented random bit extraction, experimental results show that the pixel has a flat behavior for a significant range of light intensity, which makes the pixel robust against variations of external PVT parameters. The maximum achievable bit rate has been measured equal to 1 Mbps, while random sequences are shown to pass NIST tests without any post-processing.

Light, matter, and quantum randomness generation: A relativistic quantum information perspective

We study how quantum randomness generation based on unbiased measurements on a hydrogen-like atom can get compromised by the unavoidable coupling of the atom with the electromagnetic field. We improve on previous literature by analyzing the light–atom interaction in 3+1 dimensions with no single-mode or rotating-wave approximations and taking into account the non-pointlike nature of the atom, its orbital structure, and the exchanges of angular momentum between atom and field. We show that preparing the atom in the ground state in the presence of no field excitations is not universally the safest state to generate randomness.

Generation of intensity difference squeezed state at a wavelength of 1.34 μm

The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO4 crystal operates above the threshold, an intensity difference squeezed state at a telecommunication wavelength can be obtained. The squeezing of 7.7±0.5 dB below the SNL is achieved in an analysis frequency region of 2.4–5.0 MHz.

Realization of a Quantum Random Generator Certified with the Kochen-Specker Theorem.

Random numbers are required for a variety of applications from secure communications to MonteCarlo simulation. Yet randomness is an asymptotic property, and no output string generated by a physical device can be strictly proven to be random. We report an experimental realization of a quantum random number generator (QRNG) with randomness certified by quantum contextuality and the Kochen-Specker theorem. The certification is not performed in a device-independent way but through a rigorous theoretical proof of each outcome being value indefinite even in the presence of experimental imperfections. The analysis of the generated data confirms the incomputable nature of our QRNG.

Randomness: Quantum versus classical

Recent tremendous development of quantum information theory has led to a number of quantum technological projects, e.g. quantum random generators. This development had stimulated a new wave of interest in quantum foundations. One of the most intriguing problems of quantum foundations is the elaboration of a consistent and commonly accepted interpretation of a quantum state. Closely related problem is the clarification of the notion of quantum randomness and its interrelation with classical randomness. In this short review, we shall discuss basics of classical theory of randomness (which by itself is very complex and characterized by diversity of approaches) and compare it with irreducible quantum randomness. We also discuss briefly “digital philosophy”, its role in physics (classical and quantum) and its coupling to the information interpretation of quantum mechanics (QM).

Two-slit experiment: quantum and classical probabilities

Inter-relation between quantum and classical probability models is one of the most fundamental problems of quantum foundations. Nowadays this problem also plays an important role in quantum technologies, in quantum cryptography and the theory of quantum random generators. In this letter, we compare the viewpoint of Richard Feynman that the behavior of quantum particles cannot be described by classical probability theory with the viewpoint that quantum–classical inter-relation is more complicated (cf, in particular, with the tomographic model of quantum mechanics developed in detail by Vladimir Man'ko). As a basic example, we consider the two-slit experiment, which played a crucial role in quantum foundational debates at the beginning of quantum mechanics (QM). In particular, its analysis led Niels Bohr to the formulation of the principle of complementarity. First, we demonstrate that in complete accordance with Feynman's viewpoint, the probabilities for the two-slit experiment have the non-Kolmogorovian structure, since they violate one of basic laws of classical probability theory, the law of total probability (the heart of the Bayesian analysis). However, then we show that these probabilities can be embedded in a natural way into the classical (Kolmogorov, 1933) probability model. To do this, one has to take into account the randomness of selection of different experimental contexts, the joint consideration of which led Feynman to a conclusion about the non-classicality of quantum probability. We compare this embedding of non-Kolmogorovian quantum probabilities into the Kolmogorov model with well-known embeddings of non-Euclidean geometries into Euclidean space (e.g., the Poincaré disk model for the Lobachvesky plane).

Self-testing quantum random number generator.

The generation of random numbers is a task of paramount importance in modern science. A central problem for both classical and quantum randomness generation is to estimate the entropy of the data generated by a given device. Here we present a protocol for self-testing quantum random number generation, in which the user can monitor the entropy in real time. Based on a few general assumptions, our protocol guarantees continuous generation of high quality randomness, without the need for a detailed characterization of the devices. Using a fully optical setup, we implement our protocol and illustrate its self-testing capacity. Our work thus provides a practical approach to quantum randomness generation in a scenario of trusted but error-prone devices.

Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode

We demonstrate a high bit-rate quantum random number generator by interferometric detection of phase diffusion in a gain-switched DFB laser diode. Gain switching at few-GHz frequencies produces a train of bright pulses with nearly equal amplitudes and random phases. An unbalanced Mach-Zehnder interferometer is used to interfere subsequent pulses and thereby generate strong random-amplitude pulses, which are detected and digitized to produce a high-rate random bit string. Using established models of semiconductor laser field dynamics, we predict a regime of high visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These are confirmed by measurement of pulse power statistics at the output of the interferometer. Using a 5.825 GHz excitation rate and 14-bit digitization, we observe 43 Gbps quantum randomness generation.

Quantum random bit generation using energy fluctuations in stimulated Raman scattering

Random number sequences are a critical resource in modern information processing systems, with applications in cryptography, numerical simulation, and data sampling. We introduce a quantum random number generator based on the measurement of pulse energy quantum fluctuations in Stokes light generated by spontaneously-initiated stimulated Raman scattering. Bright Stokes pulse energy fluctuations up to five times the mean energy are measured with fast photodiodes and converted to unbiased random binary strings. Since the pulse energy is a continuous variable, multiple bits can be extracted from a single measurement. Our approach can be generalized to a wide range of Raman active materials; here we demonstrate a prototype using the optical phonon line in bulk diamond.

Quantum Random Number Generation Based on Quantum Phase Noise

We experimentally demonstrate a kind of high-quantum correlated, practical quantum random generation based on the quantum phase noise of a laser, which uniformly distributes in the range of (−π, π] by driving the laser with a stream of narrow electrical pulses. We propose a working mode to further suppress the impact of phase drift after we use the passive measures (thermal and mechanical isolation) to slow it down. Moreover, a new method which ensures random numbers to be true representations of quantum characteristics is presented to quantify the quantum randomness. This scheme has an inherent advantage for multiplex generation.

All-optical quantum random bit generation from intrinsically binary phase of parametric oscillators

We demonstrate a novel all-optical quantum random number generator (RNG) based on above-threshold binary phase state selection in a degenerate optical parametric oscillator (OPO). Photodetection is not a part of the random process, and no post processing is required for the generated bit sequence. We show that the outcome is statistically random with 99% confidence, and verify that the randomness is due to the phase of initiating photons generated through spontaneous parametric down conversion of the pump, with negligible contribution of classical noise sources. With the use of micro- and nanoscale OPO resonators, this technique offers a promise for simple, robust, and high-speed on-chip all-optical quantum RNGs.

POST PROCESSING OF QUANTUM RANDOM BIT GENERATORS

This letter considers quantum random bit generators which use continuous wave (CW) or pulse lasers with Poisson characteristics. The statistical characteristics of randomly generated bits are investigated, and the efficiency of the random generators is analyzed via the bit rate.

Quantum random bit generation using stimulated Raman scattering

Random number sequences are a critical resource in a wide variety of information systems, including applications in cryptography, simulation, and data sampling. We introduce a quantum random number generator based on the phase measurement of Stokes light generated by amplification of zero-point vacuum fluctuations using stimulated Raman scattering. This is an example of quantum noise amplification using the most noise-free process possible: near unitary quantum evolution. The use of phase offers robustness to classical pump noise and the ability to generate multiple bits per measurement. The Stokes light is generated with high intensity and as a result, fast detectors with high signal-to-noise ratios can be used for measurement, eliminating the need for single-photon sensitive devices. The demonstrated implementation uses optical phonons in bulk diamond.

Note: A sampling method for quantum random bit generation

In this note, we present a new sampling method for quantum random bit generation. The new method requires only one single-photon detector and does not measure the time slots of emitted photons. A binary random bit sequence obtained is independent on the time slot of the pulses and the precision of the measurement instrument. The effect of the exclusive-or operation for eliminating the bias in the raw sequences is also discussed.

A quantum random bit generator for secure communication

A quantum random bit generator for secure communication