14 April 2014 The fastest random numbers ever

Credit: Petty Officer 2nd Class Morgan E. Dial, U.S. Navy/ Morgan Mitchell

“Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode” in Optics Express In a recent study published in Optics Express, the Quantum Optics research group, led by ICREA Prof at ICFO Morgan Mitchell, and the Optoelectronics research group, led by ICREA Prof at ICFO Valerio Pruneri, were able to build the fastest quantum random number generator to date, generating pure randomness at a rate of 43 Gbps. This study was also achieved with the collaboration of the Quantum information theory group, led by ICREA Prof at ICFO Antonio Acín, under the ERC Proof of Concept project entitled MAMBO.

Most random number generators (RNGs) are based on computer algorithms known as pseudo-random number generators, which are fast but not truly random. A short string of bits from a pseudo-RNG appears random, but eventually the sequences repeat. Moreover, if you know the inner workings of the algorithm, you can predict the exact sequence. This is troubling in communications security, where random numbers are used to choose encryption keys.

In contrast, quantum random number generators (QRNGs) extract randomness from quantum mechanical processes that are believed to be truly random and unpredictable. In this study, researchers were able to achieve a quantum number generator that gives out numbers at a rate 1000 times faster than previous QRNGs. By using phase diffusion in a DFB laser diode, they produced a train of picosecond duration pulses with nearly equal amplitudes and random phases. Then, with the help of an interferometer, they were able to interfere the pulses, generating random-amplitude pulses, which were subsequently detected and digitized to produce the high-rate random sequence of numbers.

QRNGs have important implications for improvements not only in secure communications, cryptography, and quantum key distributions but also in the the realm of computer simulations for physical, meteorological and even astrophysical scenarios.