Random bits, true and unbiased, from atmospheric turbulence

Random numbers represent a fundamental ingredient for numerical simulation, games, informa- tion science and secure communication. Algorithmic and deterministic generators are affected by insufficient information entropy. On the other hand, suitable physical processes manifest intrinsic unpredictability that may be exploited for generating genuine random numbers with an entropy reaching the ideal limit. In this work, we present a method to extract genuine random bits by using the atmospheric turbulence: by sending a laser beam along a 143Km free-space link, we took advantage of the chaotic behavior of air refractive index in the optical propagation. Random numbers are then obtained by converting in digital units the aberrations and distortions of the received laser wave-front. The generated numbers, obtained without any post-processing, pass the most selective randomness tests. The core of our extracting algorithm can be easily generalized for other physical processes

Source-Device-Independent Ultrafast Quantum Random Number Generation

Secure random numbers are a fundamental element of many applications in science, statistics, cryptography and more in general in security protocols. We present a method that enables the generation of high-speed unpredictable random numbers from the quadratures of an electromagnetic field without any assumption on the input state. The method allows us to eliminate the numbers that can be predicted due to the presence of classical and quantum side information. In particular, we introduce a procedure to estimate a bound on the conditional min-entropy based on the entropic uncertainty principle for position and momentum observables of infinite dimensional quantum systems. By the above method, we experimentally demonstrated the generation of secure true random bits at a rate greater than 1.7 Gbit/s

Loss tolerant device-independent quantum key distribution: a proof of principle

We here present the rate analysis and a proof of principle realization of a device-independent quantum key distribution (QKD) protocol requiring the lowest detection efficiency necessary to achieve a secure key compared to device-independent protocols known so far. The protocol is based on non-maximally entangled state and its experimental realization has been performed by two-photon bipartite entangled states. The improvement with respect to protocols involving maximally entangled states has been estimated.Comment: 8 pages, 4 figure + appendi

Meshing guide-lines for high fidelity CFD: an industrial application

Are investigated characteristic dimensions of turbulent flows in order to define a meshing guideline for high fidelity CFD (DNS, LES). For this purpose in the second chapter, are introduced fundaments of turbulent fields providing a general analysis of turbulent flows and introducing parameters used for turbulent analysis. In the third chapter are reviewed numerical methods for turbulence modeling, with particular regard to those applied in Chapter 5. The mesh guide-line is proposed in chapter four: after a review on turbulence scales characterization, are investigated DNS databases of relevant industrial cases where turbulence plays an important role. An in-depth analysis is provided for high delity methods such as LES and DNS. In the fifth chapter are applied knoweladges of previous chapters on a industrial case of Main Steam Line Break. Results of LES computation are validated thanks to the experimental data of ROCOM test 2.1

Quantum Randomness Certified by the Uncertainty Principle

We present an efficient method to extract the amount of true randomness that can be obtained by a Quantum Random Number Generator (QRNG). By repeating the measurements of a quantum system and by swapping between two mutually unbiased bases, a lower bound of the achievable true randomness can be evaluated. The bound is obtained thanks to the uncertainty principle of complementary measurements applied to min- and max- entropies. We tested our method with two different QRNGs, using a train of qubits or ququart, demonstrating the scalability toward practical applications.Comment: 10 page

Source-device-independent heterodyne-based quantum random number generator at 17 Gbps

For many applications, quantum random number generation should be fast and independent from assumptions on the apparatus. Here, the authors devise and implement an approach which assumes a trusted detector but not a trusted source, and allows random bit generations at ~17 Gbps using off-the-shelf components

Integrated optical modulator manipulating the polarization and rotation handedness of Orbital Angular Momentum states

AbstractRecent studies demonstrated that the optical channels encoded by Orbital Angular Momentum (OAM) are capable candidates for improving the next generation of communication systems. OAM states can enhance the capacity and security of high-dimensional communication channels in both classical and quantum regimes based on optical fibre and free space. Hence, fast and precise control of the beams encoded by OAM can provide their commercial applications in the compatible communication networks. Integrated optical devices are good miniaturized options to perform this issue. This paper proposes a numerically verified integrated high-frequency electro-optical modulator for manipulation of the guided modes encoded in both OAM and polarization states. The proposed modulator is designed as an electro-optically active Lithium Niobate (LN) core photonic wire with silica as its cladding in a LN on Insulator (LNOI) configuration. It consists of two successive parts; a phase shifter to reverse the rotation handedness of the input OAM state and a polarization converter to change the horizontally polarized OAM state to the vertically polarized one. It is shown that all four possible output polarization-OAM encoded states can be achieved with only 6 V and 7 V applied voltages to the electrodes in the two parts of the modulator.</jats:p

Experimental quantum key distribution with finite-key security analysis for noisy channels

In quantum key distribution implementations, each session is typically chosen long enough so that the secret key rate approaches its asymptotic limit. However, this choice may be constrained by the physical scenario, as in the perspective use with satellites, where the passage of one terminal over the other is restricted to a few minutes. Here we demonstrate experimentally the extraction of secure keys leveraging an optimal design of the prepare-and-measure scheme, according to recent finite-key theoretical tight-bounds. The experiment is performed in different channel conditions, and assuming two distinct attack models: individual attacks, or general quantum attacks. The request on the number of exchanged qubits is then obtained as a function of the key size and of the ambient quantum bit error rate. The results indicate that viable conditions for effective symmetric, and even one-time-pad, cryptography are achievable.Comment: 20 pages, 4 figure

Realization of a time-compensated monochromator exploiting conical diffraction for few-femtosecond XUV pulses

The general issue of the spectral selection of a portion of the wide extreme-ultraviolet spectrum obtained via extreme nonlinear processes as high order harmonic generation includes the problem of maintaining the ultrafast temporal duration of the pulses. In this paper, we present an instrument in which the pulse selection is operated in the wide wavelength range from 17 nm to above 60 nm, which is the central portion of the high-harmonics spectrum, with an instrumental function of about three femtoseconds. The design of the monochromator is based on the conical diffraction, which realizes very high diffraction efficiency by exploiting the specular reflection on the grating facets long-wise illuminated. The optical layout makes use of two gratings in the compensated-monochromator scheme already presented by the authors. The discussion of the residual aberration is also presented, with the aims to investigate the ultimate temporal resolution obtainable by this scheme